### WebCommonUtil: Web Request Utility

Source: https://github.com/drchhun/jexframe/blob/main/test.html

WebCommonUtil simplifies servlet request and response handling in web applications. It provides methods to retrieve input domains, create output domains, and access session data. It is typically instantiated using `WebCommonUtil.getInstance(request, response)`.

```Java
// In a servlet or action class
WebCommonUtil util = WebCommonUtil.getInstance(request, response);

// Read incoming parameters
JexData input = util.getInputDomain();

// Prepare output
JexData output = util.createResultDomain();
output.put("STATUS", "OK");

// Send back
util.createResultDomain().put("DATA", output.toJSON());
```

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

### JexConnectionManager: Create IDO Connection

Source: https://github.com/drchhun/jexframe/blob/main/test.html

JexConnectionManager acts as a factory for creating database and session connections. It is essential to call `createIDOConnection()` to obtain a `JexConnection` instance before executing any IDO operations.

```Java
// Acquire a connection to run IDO queries
JexConnection conn = JexConnectionManager.createIDOConnection();
```

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

### StringUtil: String Manipulation Helpers

Source: https://github.com/drchhun/jexframe/blob/main/test.html

StringUtil offers common methods for string manipulation, including conversion, null-safety, and message building. It provides utilities like `null2Void` for default values, `toInt` for safe integer parsing, and `append` for concatenating strings and other types.

```Java
String id = StringUtil.null2Void(request.getParameter("id"), "N/A");
int page = StringUtil.toInt(request.getParameter("page"), 1);
String full = StringUtil.append("User:", id, "|Page:", page);
```

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

### DomainUtil: Error & Validation Helper

Source: https://github.com/drchhun/jexframe/blob/main/test.html

DomainUtil provides utility methods for checking and extracting errors from `JexData` or lists, helping to keep action code concise. It includes functions like `isError`, `getErrorCode`, and `getErrorMessage` to streamline error handling after IDO calls.

```Java
// After an IDO call: 
if (DomainUtil.isError(idoOut)) {
  String code = DomainUtil.getErrorCode(idoOut);
  String msg = DomainUtil.getErrorMessage(idoOut);
  throw new JexWebBIZException("Error " + code + ": " + msg);
}
```

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

### JexData: Core Data Container for IDO Parameters

Source: https://github.com/drchhun/jexframe/blob/main/test.html

JexData is a JSON-compatible key/value store used for request and response payloads in JexFrame. It facilitates building IDO parameters, reading service outputs, and nesting sub-data. It supports putting and retrieving various data types and merging other JexData objects.

```Java
// Create and populate an IDO input object
JexData idoIn = util.createIDOData("TB_BOOK_L001");
idoIn.put("BOOK_ID", "B001");
idoIn.put("END_PAGE_NO", 50);

// Read a single record response
JexData result = conn.execute(idoIn);
String title = result.getString("BOOK_TITLE");
System.out.println("Title: " + title);

// Merge another JexData
JexData extras = new JexData();
extras.put("CATEGORY", "Fiction");
idoIn.putAll(extras);
```

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

### JexConnection: Transactional Query Executor

Source: https://github.com/drchhun/jexframe/blob/main/test.html

JexConnection manages the execution of `JexData` payloads and transaction boundaries. It supports both single-record (`execute`) and multi-record (`executeList`) calls. Proper transaction management with `beginTransaction`, `commit`, `rollback`, and `endTransaction` is crucial for data integrity.

```Java
conn.beginTransaction();
try {
  // Single-record call
  JexData out = conn.execute(idoIn);
  // Multi-record call
  JexDataList list = conn.executeList(idoIn);
  conn.commit();
} catch (Exception e) {
  conn.rollback();
  throw e;
} finally {
  conn.endTransaction();
}
```

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

### JexException Hierarchy: Error Signaling

Source: https://github.com/drchhun/jexframe/blob/main/test.html

The JexException hierarchy defines base classes and subtypes for signaling controlled business logic errors or transaction rollbacks. Uncaught exceptions within this hierarchy can trigger automatic rollbacks, ensuring data consistency.

```Java
// Business logic error
throw new JexBIZException("Invalid data");

// Web-layer error
throw new JexWebBIZException(idoOut);

// Transaction rollback
throw new JexTransactionRollbackException("DB failure")
```

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