Javassist

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Javassist is a Java bytecode manipulation library that enables runtime class modification and...
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### Example: Adding a Default Constructor

Source: https://www.javassist.org/html/javassist/bytecode/MethodInfo.html

Example code demonstrating how to add a default constructor to a class using MethodInfo, Bytecode, and ClassFile.

```APIDOC
## Example: Adding a Default Constructor

```java
ClassFile cf = ...; // Assume cf is an existing ClassFile object
ConstPool cp = cf.getConstPool();

Bytecode code = new Bytecode(cp);
code.addAload(0);
code.addInvokespecial("java/lang/Object", MethodInfo.nameInit, "()V");
code.addReturn(null);
code.setMaxLocals(1);

MethodInfo minfo = new MethodInfo(cp, MethodInfo.nameInit, "()V");
minfo.setCodeAttribute(code.toCodeAttribute());
cf.addMethod(minfo);
```
```

--------------------------------

### Bytecode Sequence Example

Source: https://www.javassist.org/html/javassist/bytecode/Bytecode.html

This represents the generated bytecode sequence for the previous example, consisting of iconst_3 and ireturn.

```assembly
iconst_3
 ireturn
```

--------------------------------

### Configure ProxyFactory writeReplace Method Installation

Source: https://www.javassist.org/html/javassist/util/proxy/ProxyFactory.html

Configures whether this factory should install a `writeReplace` method in created classes for serialization.

```java
public void setUseWriteReplace(boolean useWriteReplace)
```

--------------------------------

### Viewer Main Method

Source: https://www.javassist.org/html/javassist/tools/web/Viewer.html

Entry point for starting the Viewer application.

```java
public static void main(java.lang.String[] args)
                 throws java.lang.Throwable
```

--------------------------------

### Loader Usage Example with Translator

Source: https://www.javassist.org/html/javassist/Loader.html

Example demonstrating how to use the Javassist Loader with a Translator to modify class files during runtime.

```APIDOC
## Using Javassist Loader with a Translator

### Description
This example shows how to set up a Javassist `Loader` with a custom `Translator` to modify classes before they are loaded. The `run()` method is then used to execute the main application class.

### Example Code
```java
import javassist.*;

public class Main {
  public static void main(String[] args) throws Throwable {
    MyTranslator myTrans = new MyTranslator(); // Assuming MyTranslator implements javassist.Translator
    ClassPool cp = ClassPool.getDefault();
    Loader cl = new Loader(cp);
    cl.addTranslator(cp, myTrans);
    cl.run("MyApp", args); // "MyApp" is the main class to execute
  }
}
```

### Execution
To run this program, compile and execute the `Main` class:
```bash
% java Main _arg1_ _arg2_...
```
This will execute `MyApp` with modifications applied by `MyTranslator` at load time.
```

--------------------------------

### Viewer Usage Example

Source: https://www.javassist.org/html/javassist/tools/web/Viewer.html

Demonstrates how to use the Viewer class to run a remote program.

```APIDOC
## Usage Example

To run a program, use the following command:

```bash
java javassist.tools.web.Viewer _host port_ Main arg1, ...
```

This command calls `Main.main()` with `arg1,...`. All classes, including `Main`, are fetched from a server `http://_host_:_port_`. Only the class file for `Viewer` must exist on the client side.

Example of accessing Viewer methods from a loaded program:

```java
Viewer v = (Viewer)this.getClass().getClassLoader();
String port = v.getPort();
```
```

--------------------------------

### HotSwapAgent Entry Point

Source: https://www.javassist.org/html/index-all.html

The entry point for the HotSwapAgent when started after the JVM.

```APIDOC
## agentmain(String, Instrumentation)

### Description
The entry point invoked when this agent is started after the JVM starts.

### Method
Static method

### Endpoint
N/A (Static method)

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
N/A

### Response
N/A
```

--------------------------------

### ClassFileWriter.MethodWriter.begin

Source: https://www.javassist.org/html/javassist/bytecode/class-use/ClassFileWriter.AttributeWriter.html

Starts the definition of a new method using an AttributeWriter.

```APIDOC
## MethodWriter.begin

### Description
Starts adding a new method to the class.

### Parameters
#### Request Body
- **accessFlags** (int) - Required - The access flags for the method.
- **name** (int/String) - Required - The name of the method.
- **descriptor** (int/String) - Required - The method descriptor.
- **exceptions** (int[]/String[]) - Required - The exceptions thrown by the method.
- **aw** (ClassFileWriter.AttributeWriter) - Required - The attribute writer for the method.
```

--------------------------------

### Get Parameter List Descriptor

Source: https://www.javassist.org/html/javassist/bytecode/Descriptor.html

Creates a descriptor string representing a list of parameter types. For example, `(II)` for two integers.

```java
public static java.lang.String ofParameters(CtClass[] paramTypes)
```

--------------------------------

### Implement AttributeWriter to Write Synthetic Attribute

Source: https://www.javassist.org/html/javassist/bytecode/ClassFileWriter.AttributeWriter.html

Example of implementing the AttributeWriter interface to write a synthetic attribute. Requires a ConstPoolWriter to get the tag for the attribute name.

```java
ConstPoolWriter cpw = ...;
 final int tag = cpw.addUtf8Info("Synthetic");
 AttributeWriter aw = new AttributeWriter() {
     public int size() {
         return 1;
     }
     public void write(DataOutputStream out) throws java.io.IOException {
         out.writeShort(tag);
         out.writeInt(0);
     }
 };
 
```

--------------------------------

### Webserver Method: main

Source: https://www.javassist.org/html/javassist/tools/web/Webserver.html

Starts a web server. The port number is provided as the first argument. This method can throw an IOException.

```java
public static void main(java.lang.String[] args)
                 throws java.io.IOException
```

--------------------------------

### Execute Dump Tool

Source: https://www.javassist.org/html/javassist/tools/Dump.html

Example of how to run the Dump tool from the command line to inspect a class file.

```bash
% java javassist.tools.Dump foo.class
```

--------------------------------

### Alternative Startup Program using Reflection Class

Source: https://www.javassist.org/html/javassist/tools/reflect/Loader.html

This alternative program uses the Reflection class and a Javassist Loader with a specific ClassPool to achieve similar reflective capabilities.

```java
public class Main3 {
  public static void main(String[] args) throws Throwable {
    Reflection reflection = new Reflection();
    javassist.Loader cl
        = new javassist.Loader(ClassPool.getDefault(reflection));
    reflection.makeReflective("Person", "MyMetaobject",
                              "javassist.tools.reflect.ClassMetaobject");
    cl.run("MyApp", args);
  }
 }
```

--------------------------------

### Startup Program for Reflective Classes (Method 1)

Source: https://www.javassist.org/html/javassist/tools/reflect/Loader.html

Use this startup program when the Main class is loaded by javassist.tools.reflect.Loader, ensuring it shares the same security domain.

```java
public class Main {
  public static void main(String[] args) throws Throwable {
    javassist.tools.reflect.Loader cl
        = (javassist.tools.reflect.Loader)Main.class.getClassLoader();
    cl.makeReflective("Person", "MyMetaobject",
                      "javassist.tools.reflect.ClassMetaobject");
    cl.run("MyApp", args);
  }
 }
```

--------------------------------

### Get Next Instruction Index

Source: https://www.javassist.org/html/javassist/bytecode/CodeIterator.html

Returns the index of the next instruction, not the operand. The index is into the byte array obtained from get().getCode(). Throws BadBytecode if there are no more instructions.

```java
public int next() throws BadBytecode
```

--------------------------------

### run Method

Source: https://www.javassist.org/html/javassist/tools/web/Webserver.html

Begins the HTTP service.

```APIDOC
## run

### Description
Begins the HTTP service.

### Method
public

### Endpoint
/

### Response
#### Success Response (200)
- **status** (string) - Indicates the service has started.

#### Response Example
```json
{
  "status": "HTTP service started"
}
```
```

--------------------------------

### Loader Usage Example for Class Modification

Source: https://www.javassist.org/html/javassist/Loader.html

Example demonstrating how to use the Javassist Loader to modify a specific class (e.g., changing its superclass) without a separate Translator.

```APIDOC
## Using Javassist Loader for Direct Class Modification

### Description
This example illustrates how to directly modify a specific class using Javassist `CtClass` and then load it using the `Loader`. This is useful when only a few classes require modification.

### Example Code
```java
import javassist.*;

// Assuming MyApp is the main class to execute and test.Rectangle and test.Point exist
// ClassPool cp = ClassPool.getDefault();
// Loader cl = new Loader(cp);
// CtClass ct = cp.get("test.Rectangle");
// ct.setSuperclass(cp.get("test.Point"));
// cl.run("MyApp", args);
```

### Explanation
In this scenario, `test.Rectangle`'s superclass is changed to `test.Point` before `MyApp` is executed. This modification is applied directly to the `CtClass` object obtained from the `ClassPool`.
```

--------------------------------

### Creating a Proxy Class and Instance

Source: https://www.javassist.org/html/javassist/util/proxy/ProxyFactory.html

Demonstrates how to use ProxyFactory to create a proxy class, instantiate it, and set a method handler.

```APIDOC
## Creating and Using Proxies

### Example Usage
```java
ProxyFactory f = new ProxyFactory();
f.setSuperclass(Foo.class);
f.setFilter(new MethodFilter() {
    public boolean isHandled(Method m) {
        // ignore finalize()
        return !m.getName().equals("finalize");
    }
});
Class c = f.createClass();
MethodHandler mi = new MethodHandler() {
    public Object invoke(Object self, Method m, Method proceed, Object[] args) throws Throwable {
        System.out.println("Name: " + m.getName());
        return proceed.invoke(self, args);  // execute the original method.
    }
};
Foo foo = (Foo)c.newInstance();
((Proxy)foo).setHandler(mi);

// Method call on the proxy instance
foo.bar(); 
```

### Instantiating with MethodHandler
Alternatively, you can use the `create` helper method to generate, instantiate, and set the method handler in one step:
```java
Foo foo = (Foo)f.create(new Class[0], new Object[0], mi);
```

### Setting Method Handler at Runtime
To change the method handler of an existing proxy instance:
```java
MethodHandler mi = ... ;    // alternative handler
((Proxy)foo).setHandler(mi);
```
```

--------------------------------

### Startup Program for Reflective Classes (Method 2)

Source: https://www.javassist.org/html/javassist/tools/reflect/Loader.html

Use this startup program when the Main2 class is not loaded by javassist.tools.reflect.Loader, placing it in a different security domain.

```java
public class Main2 {
  public static void main(String[] args) throws Throwable {
    javassist.tools.reflect.Loader cl = new javassist.tools.reflect.Loader();
    cl.makeReflective("Person", "MyMetaobject",
                      "javassist.tools.reflect.ClassMetaobject");
    cl.run("MyApp", args);
  }
 }
```

--------------------------------

### Check if ProxyFactory Installs writeReplace Method

Source: https://www.javassist.org/html/javassist/util/proxy/ProxyFactory.html

Returns `true` if this factory installs a `writeReplace` method in created classes, enabling conventional serialization. Returns `false` otherwise.

```java
public boolean isUseWriteReplace()
```

--------------------------------

### Custom ClassMap Implementation Example

Source: https://www.javassist.org/html/javassist/ClassMap.html

Define a subclass of ClassMap to implement a custom mapping algorithm. This example demonstrates mapping 'java.' prefixed class names to 'java2.' prefixed names.

```java
class MyClassMap extends ClassMap {
   public Object get(Object jvmClassName) {
     String name = toJavaName((String)jvmClassName);
     if (name.startsWith("java."))
         return toJvmName("java2." + name.substring(5));
     else
         return super.get(jvmClassName);
   }
 }
```

--------------------------------

### javassist.tools.web.Webserver.run()

Source: https://www.javassist.org/html/index-all.html

Begins the HTTP service for the Webserver component.

```APIDOC
## Method run()

### Description
Begins the HTTP service.

### Method
void

### Endpoint
javassist.tools.web.Webserver.run()
```

--------------------------------

### Add exception table entry with CtClass

Source: https://www.javassist.org/html/javassist/bytecode/Bytecode.html

Adds a new entry to the exception table, specifying the start and end of the code range, the handler's starting PC, and the type of exception caught as a CtClass object.

```java
public void addExceptionHandler(int start, int end, int handler, CtClass type)
```

--------------------------------

### Create Proxy Instance with Helper Method

Source: https://www.javassist.org/html/javassist/util/proxy/ProxyFactory.html

The `create` helper method simplifies the process of generating a proxy class, instantiating it, and setting its method handler in a single call. Use this for a more concise way to obtain a configured proxy instance.

```java
Foo foo = (Foo)f.create(new Class[0], new Object[0], mi);
```

--------------------------------

### Webserver Initialization and Control

Source: https://www.javassist.org/html/javassist/tools/web/Webserver.html

Methods for initializing the web server, managing class pools, and handling lifecycle events.

```APIDOC
## Webserver Initialization

### Description
Constructs a new instance of the Webserver to serve files and instrument classes.

### Parameters
#### Path Parameters
- **port** (int/String) - Required - The port number on which the server will listen.

## addTranslator

### Description
Adds a translator to the server, which is invoked whenever a client requests a class file.

### Parameters
- **cp** (ClassPool) - Required - The ClassPool object for obtaining class files.
- **t** (Translator) - Required - The translator instance to process class files.

## end

### Description
Closes the server socket and terminates the service.

### Method
void end()

## setClassPool

### Description
Configures the server to use a specific ClassPool object for class file retrieval.

### Parameters
- **loader** (ClassPool) - Required - The ClassPool instance to be used.
```

--------------------------------

### Add exception table entry with type index

Source: https://www.javassist.org/html/javassist/bytecode/Bytecode.html

Adds a new entry to the exception table, specifying the start and end of the code range, the handler's starting PC, and the type of exception caught as a ConstPool index.

```java
public void addExceptionHandler(int start, int end, int handler, int type)
```

--------------------------------

### Example: Retrieving an Annotation

Source: https://www.javassist.org/html/javassist/bytecode/AnnotationsAttribute.html

Demonstrates how to retrieve a specific annotation (e.g., 'Author') from a MethodInfo object.

```APIDOC
## Example: Retrieving an Annotation

This code snippet retrieves an annotation of the type `Author` from the `MethodInfo` object specified by `minfo`. Then, it prints the value of `name` in `Author`.

```java
import javassist.bytecode.annotation.Annotation;
import javassist.bytecode.MethodInfo;
import javassist.bytecode.AnnotationsAttribute;
import javassist.bytecode.annotation.StringMemberValue;

// Assume 'm' is a CtMethod and 'minfo' is its MethodInfo object
// MethodInfo minfo = m.getMethodInfo(); 

AnnotationsAttribute attr = (AnnotationsAttribute) minfo.getAttribute(AnnotationsAttribute.invisibleTag);
Annotation an = attr.getAnnotation("Author");
String s = ((StringMemberValue)an.getMemberValue("name")).getValue();
System.out.println("@Author(name=" + s + ")"); 
```

**Note:** If the annotation is runtime visible, use `AnnotationsAttribute.visibleTag` instead of `AnnotationsAttribute.invisibleTag`.
```

--------------------------------

### GET /getSuperclass

Source: https://www.javassist.org/html/javassist/CtClass.html

Obtains the superclass of the class.

```APIDOC
## GET /getSuperclass

### Description
Obtains the class object representing the superclass of the class. Returns null if the class is java.lang.Object.

### Method
GET

### Response
#### Success Response (200)
- **return** (CtClass) - The superclass object.

### Errors
- **NotFoundException** - Thrown if the superclass cannot be found.
```

--------------------------------

### Add exception table entry with class name

Source: https://www.javassist.org/html/javassist/bytecode/Bytecode.html

Adds a new entry to the exception table, specifying the start and end of the code range, the handler's starting PC, and the type of exception caught as a class name string.

```java
public void addExceptionHandler(int start, int end, int handler, java.lang.String type)
```

--------------------------------

### Webserver Class and Constructors

Source: https://www.javassist.org/html/index-all.html

Information about the Webserver class and its constructors for running sample programs.

```APIDOC
## Webserver - Class in javassist.tools.web

### Description
A web server for running sample programs.

## Webserver(int) - Constructor for class javassist.tools.web.Webserver

### Description
Constructs a web server.

## Webserver(String) - Constructor for class javassist.tools.web.Webserver

### Description
Constructs a web server.
```

--------------------------------

### Example of using ExprEditor to inspect method calls

Source: https://www.javassist.org/html/javassist/expr/ExprEditor.html

This example demonstrates how to use ExprEditor to inspect all method calls within a CtMethod. It prints the names and line numbers of methods declared in the 'Point' class without modifying the method body.

```java
CtMethod cm = ...;
cm.instrument(new ExprEditor() {
    public void edit(MethodCall m) throws CannotCompileException {
        if (m.getClassName().equals("Point")) {
            System.out.println(m.getMethodName() + " line: "
                               + m.getLineNumber());
    }
});
```

--------------------------------

### Initialize ClassPool with System Path Option

Source: https://www.javassist.org/html/javassist/ClassPool.html

Creates a root class pool, optionally appending the system search path if the useDefaultPath parameter is true.

```java
public ClassPool(boolean useDefaultPath)
```

--------------------------------

### Method: main

Source: https://www.javassist.org/html/javassist/tools/reflect/Loader.html

Static entry point to load a class and execute its main method using the reflective loader.

```APIDOC
## Method: main

### Description
Loads a class with an instance of Loader and calls the main() method in that class.

### Parameters
- **args** (String[]) - Command line parameters. args[0] is the class name to be loaded, args[1..n] are parameters passed to the target main().

### Throws
- java.lang.Throwable
```

--------------------------------

### GET /lookupCflow

Source: https://www.javassist.org/html/index-all.html

Looks up a cflow definition in the ClassPool.

```APIDOC
## GET /lookupCflow

### Description
Undocumented method to lookup cflow.

### Method
GET

### Endpoint
/lookupCflow

### Parameters
#### Query Parameters
- **name** (String) - Required - The name of the cflow to lookup.
```

--------------------------------

### Sample Class - Constructor

Source: https://www.javassist.org/html/javassist/tools/reflect/Sample.html

Details the constructor for the Sample class.

```APIDOC
## Constructor: Sample

### Description
Initializes a new instance of the Sample class.

### Signature
```java
public Sample()
```
```

--------------------------------

### GET /getInterfaces

Source: https://www.javassist.org/html/javassist/CtClass.html

Obtains the interfaces implemented by the class.

```APIDOC
## GET /getInterfaces

### Description
Obtains the class objects representing the interfaces implemented by the class.

### Method
GET

### Response
#### Success Response (200)
- **return** (CtClass[]) - Array of implemented interfaces.

### Errors
- **NotFoundException** - Thrown if interfaces cannot be found.
```

--------------------------------

### Begin Method Definition

Source: https://www.javassist.org/html/javassist/bytecode/ClassFileWriter.MethodWriter.html

Starts the definition of a new method using either string-based or constant pool index-based parameters.

```java
public void begin(int accessFlags,
                  java.lang.String name,
                  java.lang.String descriptor,
                  java.lang.String[] exceptions,
                  ClassFileWriter.AttributeWriter aw)
```

```java
public void begin(int accessFlags,
                  int name,
                  int descriptor,
                  int[] exceptions,
                  ClassFileWriter.AttributeWriter aw)
```

--------------------------------

### GET /getName

Source: https://www.javassist.org/html/javassist/CtClass.html

Obtains the fully-qualified name of the class.

```APIDOC
## GET /getName

### Description
Obtains the fully-qualified name of the class.

### Method
GET

### Response
#### Success Response (200)
- **name** (String) - The fully-qualified class name.
```

--------------------------------

### Obtain a Control Flow Graph

Source: https://www.javassist.org/html/javassist/bytecode/analysis/ControlFlow.html

Demonstrates how to initialize a ControlFlow instance from a CtMethod and retrieve its basic blocks.

```java
CtMethod m = ...
 ControlFlow cf = new ControlFlow(m);
 Block[] blocks = cf.basicBlocks();
 
```

--------------------------------

### GET /isFrozen

Source: https://www.javassist.org/html/javassist/CtClass.html

Checks if the class is frozen and cannot be modified.

```APIDOC
## GET /isFrozen

### Description
Returns true if the class has been loaded or written out and thus it cannot be modified any more.

### Method
GET

### Response
#### Success Response (200)
- **frozen** (boolean) - True if the class is frozen.
```

--------------------------------

### Run Viewer via Command Line

Source: https://www.javassist.org/html/javassist/tools/web/Viewer.html

Execute the Viewer application to load and run a main class from a remote server.

```bash
% java javassist.tools.web.Viewer _host port_ Main arg1, ...
```

--------------------------------

### GET /isModified

Source: https://www.javassist.org/html/javassist/CtClass.html

Checks if the class definition has been modified.

```APIDOC
## GET /isModified

### Description
Returns true if the definition of the class has been modified.

### Method
GET

### Response
#### Success Response (200)
- **modified** (boolean) - True if modified, false otherwise.
```

--------------------------------

### Example: Creating a New AnnotationAttribute

Source: https://www.javassist.org/html/javassist/bytecode/AnnotationsAttribute.html

Shows how to create and add a new AnnotationAttribute to a ClassFile object.

```APIDOC
## Example: Creating a New AnnotationAttribute

This snippet demonstrates how to record a new AnnotationAttribute object.

```java
import javassist.bytecode.ClassFile;
import javassist.bytecode.ConstPool;
import javassist.bytecode.AnnotationsAttribute;
import javassist.bytecode.annotation.Annotation;
import javassist.bytecode.annotation.StringMemberValue;

// Assume 'cf' is a ClassFile object
// ClassFile cf = ... ;
ConstPool cp = cf.getConstPool();
AnnotationsAttribute attr = new AnnotationsAttribute(cp, AnnotationsAttribute.visibleTag);
Annotation a = new Annotation("Author", cp);
a.addMemberValue("name", new StringMemberValue("Chiba", cp));
attr.setAnnotation(a);
cf.addAttribute(attr);
cf.setVersionToJava5(); // Necessary if compiled with JDK 1.4 or earlier
```
```

--------------------------------

### Running Reflective Application (Method 1)

Source: https://www.javassist.org/html/javassist/tools/reflect/Loader.html

Command to run the application using the Main class, which is loaded by javassist.tools.reflect.Loader.

```bash
% java javassist.tools.reflect.Loader Main arg1, ...
```

--------------------------------

### GET /getURL

Source: https://www.javassist.org/html/javassist/CtClass.html

Retrieves the URL of the class file.

```APIDOC
## GET /getURL

### Description
Returns the uniform resource locator (URL) of the class file.

### Method
GET

### Response
#### Success Response (200)
- **URL** (java.net.URL) - The URL of the class file.

### Errors
- **NotFoundException** - Thrown if the URL cannot be found.
```

--------------------------------

### Get Array Dimension

Source: https://www.javassist.org/html/javassist/bytecode/SignatureAttribute.ArrayType.html

Retrieves the dimension of the array.

```java
public int getDimension()
```

--------------------------------

### Run Compiler from Command Line

Source: https://www.javassist.org/html/javassist/tools/reflect/Compiler.html

Example usage of the Compiler class to modify class files with specific metaobject configurations.

```bash
% java Compiler Dog -m MetaDog -c CMetaDog Cat -m MetaCat Cow
```

--------------------------------

### Sample Class Methods

Source: https://www.javassist.org/html/javassist/tools/rmi/Sample.html

Details the instance and static methods of the Sample class.

```APIDOC
## forward(Object[] args, int identifier)

### Description
Handles method invocation forwarding for instance methods.

### Method
Instance Method

### Endpoint
N/A

### Parameters
- **args** (Object[]) - Arguments for the method call.
- **identifier** (int) - Identifier for the method.

### Request Body
None

### Response
- **return value** (Object) - The result of the method invocation.

### Request Example
```java
// Example usage within a proxy context
Object result = sample.forward(methodArgs, methodIdentifier);
```

## forwardStatic(Object[] args, int identifier)

### Description
Handles method invocation forwarding for static methods.

### Method
Static Method

### Endpoint
N/A

### Parameters
- **args** (Object[]) - Arguments for the method call.
- **identifier** (int) - Identifier for the method.

### Request Body
None

### Response
- **return value** (Object) - The result of the method invocation.

### Throws
- **RemoteException** - If a remote communication error occurs.

### Request Example
```java
// Example usage within a proxy context for static methods
Object result = Sample.forwardStatic(methodArgs, methodIdentifier);
```
```

--------------------------------

### Get number of parameters

Source: https://www.javassist.org/html/javassist/bytecode/ParameterAnnotationsAttribute.html

Returns the num_parameters value.

```java
public int numParameters()
```

--------------------------------

### Implement Singleton Pattern with createPoint

Source: https://www.javassist.org/html/javassist/CodeConverter.html

Example of a static method used to intercept instantiation and implement a singleton pattern.

```java
public static Point createPoint(int x, int y) {
     if (aPoint == null)
         aPoint = new Point(x, y);
     return aPoint;
 }
```

--------------------------------

### Get Code Bytes

Source: https://www.javassist.org/html/javassist/bytecode/CodeAttribute.html

Returns the code array.

```java
public byte[] getCode()
```

--------------------------------

### Get Max Locals

Source: https://www.javassist.org/html/javassist/bytecode/CodeAttribute.html

Returns the value of max_locals.

```java
public int getMaxLocals()
```

--------------------------------

### Get Max Stack

Source: https://www.javassist.org/html/javassist/bytecode/CodeAttribute.html

Returns the value of max_stack.

```java
public int getMaxStack()
```

--------------------------------

### Constructor Detail: MethodInfo

Source: https://www.javassist.org/html/javassist/bytecode/MethodInfo.html

Details for the `MethodInfo` constructor.

```APIDOC
## Constructor Detail: MethodInfo

### `public MethodInfo(ConstPool cp, java.lang.String methodname, java.lang.String desc)`

Constructs a `method_info` structure.
```

--------------------------------

### Main Method - Dump.main()

Source: https://www.javassist.org/html/javassist/tools/Dump.html

The `main` method is the entry point for the Dump tool, accepting command-line arguments to specify the class file to process.

```APIDOC
## Dump.main()

### Description
This is the main method for the `javassist.tools.Dump` class. It serves as the entry point for executing the Dump tool from the command line. It processes the provided class file and outputs its structural information.

### Method
`public static void main(java.lang.String[] args)`

### Endpoint
N/A (This is a static method within the Dump class)

### Parameters
#### Method Parameters
- **`args`** (java.lang.String[]) - Required - An array of strings representing command-line arguments. `args[0]` is expected to be the path to the class file to be dumped.

### Throws
- **`java.lang.Exception`** - This exception may be thrown if an error occurs during the processing of the class file.

### Request Example
(This is a method signature, not a direct request example. See Dump Tool Usage for command-line execution.)

### Response
#### Success Response
- The method executes the Dump tool's functionality, printing class file details to standard output.

#### Response Example
(See Dump Tool Usage for example output.)
```

--------------------------------

### CtClass getAccessorMaker()

Source: https://www.javassist.org/html/index-all.html

Undocumented method to get an accessor maker.

```APIDOC
## GET CtClass.getAccessorMaker()

### Description
Undocumented method.

### Method
GET

### Endpoint
N/A (Method within a class)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response (200)
- **Object** - The accessor maker.

#### Response Example
```json
{
  "accessorMakerType": "DefaultAccessorMaker"
}
```
```

--------------------------------

### ProxyFactory.ClassLoaderProvider get(ProxyFactory)

Source: https://www.javassist.org/html/index-all.html

Returns a class loader from the ProxyFactory.

```APIDOC
## GET ProxyFactory.ClassLoaderProvider.get(ProxyFactory)

### Description
Returns a class loader.

### Method
GET

### Endpoint
N/A (Method within an interface implementation)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response (200)
- **ClassLoader** - The ClassLoader instance.

#### Response Example
```json
{
  "classLoaderName": "sun.misc.Launcher$AppClassLoader"
}
```
```

--------------------------------

### Field Detail: nameInit

Source: https://www.javassist.org/html/javassist/bytecode/MethodInfo.html

Details for the `nameInit` static String field.

```APIDOC
## Field Detail: nameInit

### `public static final java.lang.String nameInit`

The name of constructors: `<init>`.

See Also:
    Constant Field Values
```

--------------------------------

### Type get(CtClass)

Source: https://www.javassist.org/html/index-all.html

Obtains the Type for a given class.

```APIDOC
## GET Type.get(CtClass)

### Description
Obtain the Type for a given class.

### Method
GET

### Endpoint
N/A (Static method within a class)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response (200)
- **Type** - The Type object representing the class.

#### Response Example
```json
{
  "typeName": "com.example.MyClass",
  "isPrimitive": false
}
```
```

--------------------------------

### GET /javassist/URLClassPath/fetchClass

Source: https://www.javassist.org/html/index-all.html

Reads a class file from an HTTP server.

```APIDOC
## GET /javassist/URLClassPath/fetchClass

### Description
Reads a class file on an http server.

### Method
GET

### Parameters
#### Query Parameters
- **classname** (String) - Required - The name of the class to fetch.
- **port** (int) - Required - The port number of the server.
- **directory** (String) - Required - The directory path on the server.
- **file** (String) - Required - The filename of the class file.
```

--------------------------------

### Method Detail: accept(MemberValueVisitor visitor)

Source: https://www.javassist.org/html/javassist/bytecode/annotation/LongMemberValue.html

Details on how to accept a MemberValueVisitor.

```APIDOC
#### accept
```java
public void accept(MemberValueVisitor visitor)
```

Accepts a visitor.

Specified by: `accept` in class `MemberValue`
```

--------------------------------

### GET Metalevel._getMetaobject()

Source: https://www.javassist.org/html/javassist/tools/reflect/class-use/Metaobject.html

Retrieves the metaobject currently associated with the object.

```APIDOC
## GET Metalevel._getMetaobject()

### Description
Obtains the metaobject associated with this object.

### Method
GET

### Endpoint
Metalevel._getMetaobject()

### Response
#### Success Response (200)
- **Metaobject** - The metaobject associated with the object.
```

--------------------------------

### FieldInfo Constructor and Usage Example

Source: https://www.javassist.org/html/javassist/bytecode/FieldInfo.html

Demonstrates how to create and add a new public integer field named 'width' to a class file using FieldInfo.

```APIDOC
## FieldInfo Constructor and Usage

### Description
This section shows how to construct a `FieldInfo` object and add it to a `ClassFile`.

### Method
`FieldInfo(ConstPool cp, String fieldName, String desc)`

### Endpoint
N/A (Class method)

### Parameters
#### Constructor Parameters
- **cp** (ConstPool) - The constant pool table.
- **fieldName** (String) - The name of the field.
- **desc** (String) - The descriptor of the field.

### Request Example
```java
ClassFile cf = ...; // Assume cf is an initialized ClassFile object
FieldInfo f = new FieldInfo(cf.getConstPool(), "width", "I");
f.setAccessFlags(AccessFlag.PUBLIC);
cf.addField(f);
```

### Response
N/A (This is a code example demonstrating object creation and manipulation.)
```

--------------------------------

### Sample Class Constructor

Source: https://www.javassist.org/html/javassist/tools/rmi/Sample.html

Details the default constructor for the Sample class.

```APIDOC
## Sample()

### Description
Default constructor for the Sample class.

### Method
Constructor

### Endpoint
N/A

### Parameters
None

### Request Body
None

### Response
None

### Constructor Example
```java
Sample sample = new Sample();
```
```

--------------------------------

### GET SignatureAttribute.ClassSignature.getParameters

Source: https://www.javassist.org/html/javassist/bytecode/class-use/SignatureAttribute.TypeParameter.html

Retrieves the type parameters from a class signature.

```APIDOC
## GET SignatureAttribute.ClassSignature.getParameters

### Description
Returns the type parameters associated with the class signature.

### Method
GET

### Response
- **SignatureAttribute.TypeParameter[]** - An array of type parameters.
```

--------------------------------

### GET /getDeclaringClass

Source: https://www.javassist.org/html/javassist/CtClass.html

Returns the enclosing class if this is a member class.

```APIDOC
## GET /getDeclaringClass

### Description
If this class is a member class or interface of another class, then the class enclosing this class is returned.

### Method
GET

### Response
#### Success Response (200)
- **return** (CtClass) - The enclosing class or null if top-level.

### Errors
- **NotFoundException** - Thrown if the declaring class cannot be found.
```

--------------------------------

### Proxy Class Example

Source: https://www.javassist.org/html/javassist/tools/rmi/StubGenerator.html

Illustrates the structure of a proxy class generated for a given class A. It includes methods for object import and retrieval of the object ID.

```java
public class A implements Proxy, Serializable {
   private ObjectImporter importer;
   private int objectId;
   public int _getObjectId() { return objectId; }
   public A(ObjectImporter oi, int id) {
     importer = oi; objectId = id;
   }

   ... the same methods that the original class A declares ...
 }
```

--------------------------------

### GET dominatorTree()

Source: https://www.javassist.org/html/javassist/bytecode/analysis/ControlFlow.html

Constructs and returns the dominator tree for the method.

```APIDOC
## GET dominatorTree()

### Description
Constructs a dominator tree for the method. The first element of the returned array is the root of the tree.

### Response
#### Success Response (200)
- **ControlFlow.Node[]** - An array of tree nodes, or null if the method has no code.
```

--------------------------------

### Create ClassPool with Default Path

Source: https://www.javassist.org/html/javassist/ClassPool.html

Initializes a root class pool and appends the system search path. This is used to create the default singleton ClassPool.

```java
ClassPool cp = new ClassPool();
 cp.appendSystemPath();
 
```

--------------------------------

### Get Component Type

Source: https://www.javassist.org/html/javassist/bytecode/SignatureAttribute.ArrayType.html

Retrieves the component type of the array.

```java
public SignatureAttribute.Type getComponentType()
```

--------------------------------

### Translator.start

Source: https://www.javassist.org/html/javassist/Translator.html

Initializes the translator when attached to a Loader.

```APIDOC
## void start(ClassPool pool)

### Description
Is invoked by a Loader for initialization when the object is attached to the Loader object. This method can be used for getting (for caching) some CtClass objects that will be accessed in onLoad() in Translator.

### Parameters
#### Request Body
- **pool** (ClassPool) - Required - The ClassPool that this translator should use.

### Response
#### Success Response (200)
- **void** - Method completes successfully.

#### Errors
- **NotFoundException** - if a CtClass cannot be found.
- **CannotCompileException** - if the initialization by this method fails.
```

--------------------------------

### Get Exception Table

Source: https://www.javassist.org/html/javassist/bytecode/CodeAttribute.html

Returns the exception table array.

```java
public ExceptionTable getExceptionTable()
```

--------------------------------

### FactoryHelper Class Overview

Source: https://www.javassist.org/html/javassist/util/proxy/FactoryHelper.html

Provides a summary of the FactoryHelper class, its fields, constructors, and methods.

```APIDOC
## Class: javassist.util.proxy.FactoryHelper

### Description
A helper class for implementing `ProxyFactory`. The users of `ProxyFactory` do not have to see this class.

See Also:
`ProxyFactory`

### Field Summary
Fields Modifier and Type | Field | Description  
---|---|---  
`static int[]` | `dataSize` | The data size of primitive types.
`static java.lang.Class<?>[]` | `primitiveTypes` | `Class` objects representing primitive types.
`static java.lang.String[]` | `unwarpMethods` | The names of methods for obtaining a primitive value from a wrapper object.
`static java.lang.String[]` | `unwrapDesc` | The descriptors of the unwrapping methods contained in `unwrapMethods`.
`static java.lang.String[]` | `wrapperDesc` | The descriptors of the constructors of wrapper classes.
`static java.lang.String[]` | `wrapperTypes` | The fully-qualified names of wrapper classes for primitive types.

### Constructor Summary
Constructors Constructor | Description  
---|---  
`FactoryHelper()` | 

### Method Summary
All Methods Static Methods Concrete Methods Deprecated Methods Modifier and Type | Method | Description  
---|---|---  
`static java.lang.Class<?>` | `toClass(ClassFile cf, java.lang.Class<?> neighbor, java.lang.ClassLoader loader, java.security.ProtectionDomain domain)` | Loads a class file by a given class loader.
`static java.lang.Class<?>` | `toClass(ClassFile cf, java.lang.ClassLoader loader)` | Deprecated.
`static java.lang.Class<?>` | `toClass(ClassFile cf, java.lang.ClassLoader loader, java.security.ProtectionDomain domain)` | Deprecated.
`static java.lang.Class<?>` | `toClass(ClassFile cf, java.lang.invoke.MethodHandles.Lookup lookup)` | Loads a class file by a given lookup.
`static int` | `typeIndex(java.lang.Class<?> type)` | Returns an index for accessing arrays in this class.
`static void` | `writeFile(ClassFile cf, java.lang.String directoryName)` | Writes a class file.

### Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`
```

--------------------------------

### Get Code Length

Source: https://www.javassist.org/html/javassist/bytecode/CodeAttribute.html

Returns the length of the code array.

```java
public int getCodeLength()
```

--------------------------------

### Example of Class Mapping in CtMethod

Source: https://www.javassist.org/html/javassist/CtMethod.html

Demonstrates how class names are replaced in a method body using a ClassMap during copying.

```java
 public X at(int i) {
     return (X)super.elementAt(i);
 }
```

```java
 public String at(int i) {
     return (String)super.elementAt(i);
 }
```

--------------------------------

### Get Constant Value Index

Source: https://www.javassist.org/html/javassist/bytecode/ConstantAttribute.html

Retrieves the constantvalue_index from the attribute.

```java
public int getConstantValue()
```

--------------------------------

### Running Reflective Application (Method 2)

Source: https://www.javassist.org/html/javassist/tools/reflect/Loader.html

Command to run the application using Main2, which is not loaded by javassist.tools.reflect.Loader.

```bash
% java Main2 arg1, ...
```

--------------------------------

### GET /getParameterTypes

Source: https://www.javassist.org/html/javassist/CtBehavior.html

Obtains the parameter types of the method or constructor.

```APIDOC
## GET /getParameterTypes

### Description
Obtains parameter types of this method/constructor.

### Method
GET

### Endpoint
/getParameterTypes

### Response
#### Success Response (200)
- **CtClass[]** - Array of parameter types.

#### Errors
- **NotFoundException** - Thrown if the parameter types cannot be found.
```

--------------------------------

### make(String src, CtClass declaring, String delegateObj, String delegateMethod)

Source: https://www.javassist.org/html/javassist/CtNewMethod.html

Compiles the given source code and creates a method. If the source code includes $proceed(), then it is compiled into a method call on the specified object.

```APIDOC
## POST /ctnewmethod/make/delegate

### Description
Compiles the given source code and creates a method. If the source code includes `$proceed()`, then it is compiled into a method call on the specified object.

### Method
POST

### Endpoint
`/ctnewmethod/make/delegate`

### Parameters
#### Query Parameters
- **src** (String) - Required - The source text.
- **declaring** (CtClass) - Required - The class to which the created method is added.
- **delegateObj** (String) - Required - The source text specifying the object that is called on by `$proceed()`.
- **delegateMethod** (String) - Required - The name of the method that is called by `$proceed()`.

### Request Example
```json
{
  "src": "public Object id(Object obj) { return $proceed(obj); }",
  "declaring": "com.example.MyClass",
  "delegateObj": "super",
  "delegateMethod": "id"
}
```

### Response
#### Success Response (200)
- **CtMethod** (CtMethod) - The newly created method.

#### Response Example
```json
{
  "methodName": "id",
  "returnType": "Object",
  "parameters": ["Object"]
}
```

### Throws
- `CannotCompileException`
```

--------------------------------

### Get Constructor Name

Source: https://www.javassist.org/html/javassist/CtConstructor.html

Obtains the simple name of this constructor.

```java
java.lang.String
getName()
```

--------------------------------

### Static Method: make (Parameters and Body)

Source: https://www.javassist.org/html/javassist/CtNewConstructor.html

Creates a public constructor using specified parameters, exceptions, and a body string.

```APIDOC
## static CtConstructor make(CtClass[] parameters, CtClass[] exceptions, java.lang.String body, CtClass declaring)

### Description
Creates a public constructor.

### Parameters
- **parameters** (CtClass[]) - Required - A list of the parameter types.
- **exceptions** (CtClass[]) - Required - A list of the exception types.
- **body** (java.lang.String) - Required - The source text of the constructor body. It must be a block surrounded by {}. If it is null, the substituted constructor body does nothing except calling super().
- **declaring** (CtClass) - Required - The class to which the created method is added.

### Response
- **CtConstructor** - The created constructor object.
```

--------------------------------

### Webserver Class

Source: https://www.javassist.org/html/javassist/tools/web/package-summary.html

The Webserver class provides functionality for hosting sample programs.

```APIDOC
## Webserver

### Description
A web server implementation designed for running sample programs within the Javassist project environment.

### Exceptions
- **BadHttpRequest**: Thrown when the server receives an invalid HTTP request.
```

--------------------------------

### Define an annotation type

Source: https://www.javassist.org/html/javassist/bytecode/AnnotationDefaultAttribute.html

Example of an annotation interface with default values.

```java
 @interface Author {
   String name() default "Shakespeare";
   int age() default 99;
 }
```

--------------------------------

### StackMap Entry Count

Source: https://www.javassist.org/html/index-all.html

Method to get the number of entries in a StackMap.

```APIDOC
## StackMap Entry Count

### Method
- numOfEntries()
  Method in class javassist.bytecode.StackMap
  Returns `number_of_entries`.
```

--------------------------------

### Method Summary

Source: https://www.javassist.org/html/javassist/CtNewMethod.html

Lists all static and concrete methods available in the CtNewMethod class.

```APIDOC
### Method Summary

All Methods | Static Methods | Concrete Methods | Modifier and Type | Method | Description
---|---|---|---|---|---
 | `static CtMethod` |  | `abstractMethod(CtClass returnType, java.lang.String mname, CtClass[] parameters, CtClass[] exceptions, CtClass declaring)` | Creates a public abstract method.
 | `static CtMethod` |  | `copy(CtMethod src, java.lang.String name, CtClass declaring, ClassMap map)` | Creates a copy of a method with a new name.
 | `static CtMethod` |  | `copy(CtMethod src, CtClass declaring, ClassMap map)` | Creates a copy of a method.
 | `static CtMethod` |  | `delegator(CtMethod delegate, CtClass declaring)` | Creates a method forwarding to a delegate in a super class.
 | `static CtMethod` |  | `getter(java.lang.String methodName, CtField field)` | Creates a public getter method.
 | `static CtMethod` |  | `make(int modifiers, CtClass returnType, java.lang.String mname, CtClass[] parameters, CtClass[] exceptions, java.lang.String body, CtClass declaring)` | Creates a method.
 | `static CtMethod` |  | `make(java.lang.String src, CtClass declaring)` | Compiles the given source code and creates a method.
 | `static CtMethod` |  | `make(java.lang.String src, CtClass declaring, java.lang.String delegateObj, java.lang.String delegateMethod)` | Compiles the given source code and creates a method.
 | `static CtMethod` |  | `make(CtClass returnType, java.lang.String mname, CtClass[] parameters, CtClass[] exceptions, java.lang.String body, CtClass declaring)` | Creates a public (non-static) method.
 | `static CtMethod` |  | `setter(java.lang.String methodName, CtField field)` | Creates a public setter method.
 | `static CtMethod` |  | `wrapped(CtClass returnType, java.lang.String mname, CtClass[] parameterTypes, CtClass[] exceptionTypes, CtMethod body, CtMethod.ConstParameter constParam, CtClass declaring)` | Creates a wrapped method.
```

--------------------------------

### Descriptor Parameter Count

Source: https://www.javassist.org/html/index-all.html

Method to get the number of parameters in a descriptor.

```APIDOC
## Descriptor Parameter Count

### Method
- numOfParameters(String descriptor)
  Static method in class javassist.bytecode.Descriptor
  Returns the number of the parameters included in the given descriptor.
```

--------------------------------

### Sample Class Methods

Source: https://www.javassist.org/html/index-all.html

Methods for handling remote method invocation forwarding.

```APIDOC
## Sample Class Methods

### Description
Methods related to sample implementations for remote method invocation.

### Methods
- `forward(Object[], int)`: Forwards method calls.
- `forwardStatic(Object[], int)`: Forwards static method calls.

### Endpoint
N/A

### Parameters
- `Object[]` - Array of objects.
- `int` - An integer parameter.

### Request Example
N/A

### Response
N/A
```

--------------------------------

### Constructor Navigation

Source: https://www.javassist.org/html/javassist/bytecode/CodeIterator.html

Methods for skipping constructor initialization logic to locate specific invocation instructions.

```APIDOC
## skipConstructor
### Description
Moves to the instruction for either super() or this().

## skipSuperConstructor
### Description
Moves to the instruction for super().

## skipThisConstructor
### Description
Moves to the instruction for this().
```

--------------------------------

### Get MethodHandler

Source: https://www.javassist.org/html/javassist/util/proxy/ProxyObject.html

Retrieves the current MethodHandler associated with the proxy object.

```java
MethodHandler getHandler()
```

--------------------------------

### Sample Class - Methods

Source: https://www.javassist.org/html/javassist/tools/reflect/Sample.html

Details the methods available in the Sample class for reflective operations.

```APIDOC
## Methods: Sample Class

### trap

#### Description
Handles general reflective calls.

#### Signature
```java
public Object trap(Object[] args, int identifier) throws Throwable
```

#### Parameters
- **args** (Object[]) - Arguments for the reflective call.
- **identifier** (int) - Identifier for the method being trapped.

#### Throws
- `java.lang.Throwable`

### trapStatic

#### Description
Handles reflective calls to static methods.

#### Signature
```java
public static Object trapStatic(Object[] args, int identifier) throws Throwable
```

#### Parameters
- **args** (Object[]) - Arguments for the static reflective call.
- **identifier** (int) - Identifier for the static method being trapped.

#### Throws
- `java.lang.Throwable`

### trapRead

#### Description
Handles reflective calls to read field values.

#### Signature
```java
public static Object trapRead(Object[] args, String name)
```

#### Parameters
- **args** (Object[]) - Arguments for the reflective call.
- **name** (String) - The name of the field to read.

### trapWrite

#### Description
Handles reflective calls to write field values.

#### Signature
```java
public static Object trapWrite(Object[] args, String name)
```

#### Parameters
- **args** (Object[]) - Arguments for the reflective call.
- **name** (String) - The name of the field to write.
```

--------------------------------

### Get Port Number

Source: https://www.javassist.org/html/javassist/tools/web/Viewer.html

Retrieves the port number configured for the Viewer.

```java
public int getPort()
```

--------------------------------

### Example Usage of Analyzer

Source: https://www.javassist.org/html/javassist/bytecode/analysis/Analyzer.html

Demonstrates how to use the Analyzer to obtain frame states for a method and inspect local variables and stack types.

```java
public void analyzeIt(CtClass clazz, MethodInfo method) {
    Analyzer analyzer = new Analyzer();
    Frame[] frames = analyzer.analyze(clazz, method);
    frames[0].getLocal(0).getCtClass(); // returns clazz;
    frames[0].getLocal(1).getCtClass(); // returns java.lang.String
    frames[1].peek(); // returns Type.INTEGER
    frames[27].peek().getCtClass(); // returns java.lang.Number
 }
```

--------------------------------

### Get Server Name

Source: https://www.javassist.org/html/javassist/tools/web/Viewer.html

Retrieves the server name configured for the Viewer.

```java
public java.lang.String getServer()
```
Tokens:
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