### Custom Cell Write Converter

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Implement WriteConverter to transform cell values when writing to Excel. This example appends a string to the converted value.

```java
public class CustomizeFieldWriteConverter implements WriteConverter {

  /**
   * 写文件时，将值进行转换（此处示例为将数值拼接为指定格式的字符串）
   */
  @Override
  public String convert(Object o) throws ExcelKitWriteConverterException {
    return (o + "_convertedValue");
  }
}
```

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

### Custom Cell Read Converter

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Implement ReadConverter to transform cell values when reading from Excel. This example calculates the sum of character integer values in a string.

```java
public class CustomizeFieldReadConverter implements ReadConverter {

  /**
   * 读取单元格时，将值进行转换（此处示例为计算单元格字符串char的总和）
   */
  @Override
  public Object convert(Object o) throws ExcelKitReadConverterException {
    String value = (String) o;

    int convertedValue = 0;
    for (char c : value.toCharArray()) {
      convertedValue += Integer.valueOf(c);
    }
    return convertedValue;
  }
}
```

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

### Custom Dropdown Data Source with Options Interface

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Implement the Options interface to define custom data sources for dropdown lists in Excel import templates.

```java
public class UserGroupNameOptions implements Options {

  @Override
  public String[] get() {
    return new String[]{"管理组", "普通会员组", "游客"};
  }
}
```

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

### Build Excel Import Template with One Line of Code

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Use the ExcelKit API to generate an import template. This will create comments and dropdowns based on the configuration.

```java
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import javax.servlet.http.HttpServletResponse;
import java.util.List;

// Assuming User class and DbUtil are defined elsewhere
// import com.yourpackage.User;
// import com.yourpackage.DbUtil;

@RequestMapping(value = "/downTemplate", method = RequestMethod.GET)
public void downTemplate(HttpServletResponse response) {
  List<User> userList = DbUtil.getUserList(3);
  ExcelKit.$Export(User.class, response).downXlsx(userList, true);
}
```

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

### Execute Excel Batch Export with One Line of Code

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Utilizes Apache POI SXSSF series API for optimized export performance. Generates a large dataset for testing export capabilities.

```java
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import javax.servlet.http.HttpServletResponse;
import java.util.List;

// Assuming User class, DbUtil, and log are defined elsewhere
// import com.yourpackage.User;
// import com.yourpackage.DbUtil;
// import org.slf4j.Logger;
// import org.slf4j.LoggerFactory;

// private static final Logger log = LoggerFactory.getLogger(YourController.class);

@RequestMapping(value = "/downXlsx", method = RequestMethod.GET)
public void downXlsx(HttpServletResponse response) {
  long beginMillis = System.currentTimeMillis();
  List<User> userList = DbUtil.getUserList(100000); // Generate 100,000 test data
  ExcelKit.$Export(User.class, response).downXlsx(userList, false);
  log.info("#ExcelKit.$Export success, size={},timeConsuming={}s",
      userList.size(), (System.currentTimeMillis() - beginMillis) / 1000L);
}
```

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

### Execute File Import with Streaming

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Process Excel files using a streaming approach to avoid memory issues, regardless of file size. Handles both successful and erroneous rows.

```java
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;
import java.io.IOException;
import java.util.List;
import java.util.Map;

// Assuming User class, Lists, MapUtil, CollectionUtil, ExcelReadHandler, ExcelErrorField are defined elsewhere
// import com.yourpackage.User;
// import com.google.common.collect.Lists;
// import com.yourpackage.util.MapUtil;
// import com.yourpackage.util.CollectionUtil;
// import com.yourpackage.handler.ExcelReadHandler;
// import com.yourpackage.model.ExcelErrorField;

@RequestMapping(value = "/importUser", method = RequestMethod.POST)
public ResponseEntity<?> importUser(@RequestParam MultipartFile file)
    throws IOException {
  long beginMillis = System.currentTimeMillis();

  List<User> successList = Lists.newArrayList();
  List<Map<String, Object>> errorList = Lists.newArrayList();

  ExcelKit.$Import(User.class)
      .readXlsx(file.getInputStream(), new ExcelReadHandler<User>() {

        @Override
        public void onSuccess(int sheetIndex, int rowIndex, User entity) {
          successList.add(entity); // Single row read successfully, add to import queue.
        }

        @Override
        public void onError(int sheetIndex, int rowIndex,
            List<ExcelErrorField> errorFields) {
          // Data read failed, record all failed data for the current row
          errorList.add(MapUtil.newHashMap(
              "sheetIndex", sheetIndex,
              "rowIndex", rowIndex,
              "errorFields", errorFields
          ));
        }
      });

  // TODO: Execute the import operation for successList.

  return ResponseEntity.ok(MapUtil.newHashMap(
      "data", successList,
      "haveError", !CollectionUtil.isEmpty(errorList),
      "error", errorList,
      "timeConsuming", (System.currentTimeMillis() - beginMillis) / 1000L
  ));
}
```

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

### XML Mapping Configuration for User Entity

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

XML configuration for mapping User entity fields to Excel columns. This file should be placed at classpath:excel-mapping/{entityClassName}.xml.

```xml
<?xml version="1.0" encoding="UTF-8"?>
<excel-mapping name="用户信息">
  <property name="userId" column="编号" width="30"/>
  <property
    name="username"
    column="用户名"
    required="true"
    validator="com.wuwenze.validator.UsernameValidator"
    comment="请填写用户名，最大长度为12，且不能重复"
  />
  <property name="password" column="密码" required="true" maxLength="32"/>
  <property name="email" column="邮箱" validator="com.wuwenze.validator.UserEmailValidator"/>
  <property
    name="sex"
    column="性别"
    readConverterExp="未知=0,男=1,女=2"
    writeConverterExp="0=未知,1=男,2=女"
    options="com.wuwenze.options.SexOptions"
  />
  <property name="userGroup.name" column="用户组" options="com.wuwenze.options.UserGroupNameOptions"/>
  <property name="createAt" column="创建时间" dateFormat="yyyy/MM/dd HH:mm:ss"/>
  <property
    name="customizeField"
    column="自定义字段"
    maxLength="80"
    comment="可以乱填，但是长度不能超过80，导入时最终会转换为数字"
    writeConverter="com.wuwenze.converter.CustomizeFieldWriteConverter"
    readConverter="com.wuwenze.converter.CustomizeFieldReadConverter"
  />
</excel-mapping>
```

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

### Execute File Import

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Executes file import using a streaming approach to handle large files without memory issues. It processes data row by row and handles success and error cases.

```APIDOC
## POST /importUser

### Description
Imports data from an Excel file, processing it row by row to prevent memory overflows. It separates successful imports from errors.

### Method
POST

### Endpoint
/importUser

### Parameters
#### Query Parameters
- **file** (MultipartFile) - Required - The Excel file to import.

### Request Example
```
POST /importUser HTTP/1.1
Host: example.com
Content-Type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW

------WebKitFormBoundary7MA4YWxkTrZu0gW
Content-Disposition: form-data; name="file"; filename="users.xlsx"
Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet

[Binary Excel file content]
------WebKitFormBoundary7MA4YWxkTrZu0gW--
```

### Response
#### Success Response (200)
- **data** (List<User>) - A list of successfully imported User objects.
- **haveError** (boolean) - Indicates if there were any errors during import.
- **error** (List<Map<String, Object>>) - A list of errors, each containing sheet index, row index, and error fields.
- **timeConsuming** (long) - The time taken for the import process in seconds.

#### Response Example
```json
{
  "data": [
    {
      "name": "John Doe",
      "age": 30
    }
  ],
  "haveError": false,
  "error": [],
  "timeConsuming": 2
}
```
```

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

### Generate Excel Import Template

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Generates an Excel import template based on the provided configuration. This includes features like comments and dropdowns.

```APIDOC
## GET /downTemplate

### Description
Generates an Excel import template with optional example data.

### Method
GET

### Endpoint
/downTemplate

### Parameters
None

### Request Example
None

### Response
#### Success Response (200)
- Binary stream of an Excel file (.xlsx)

#### Response Example
None
```

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

### User Entity with XML Mapping

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Defines the User entity for XML mapping. The actual mapping configuration is provided in a separate XML file.

```java
public class User2 {

  private Integer userId;
  private String username;
  private String password;
  private String email;
  private Integer sex;
  private UserGroup userGroup;
  private Date createAt;
  private Integer customizeField;
  
  // Getter and Setter ..
}
```

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

### Execute Excel Bulk Export

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Performs a bulk export of data to an Excel file (.xlsx) using Apache POI SXSSF for optimized performance, suitable for large datasets.

```APIDOC
## GET /downXlsx

### Description
Performs a bulk export of a large dataset to an Excel file (.xlsx), optimized for performance.

### Method
GET

### Endpoint
/downXlsx

### Parameters
None

### Request Example
None

### Response
#### Success Response (200)
- Binary stream of an Excel file (.xlsx) containing the exported data.

#### Response Example
None
```

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

### ExcelKit Maven Dependency

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Add this dependency to your project's pom.xml to include ExcelKit.

```xml
<dependency>
    <groupId>com.wuwenze</groupId>
    <artifactId>ExcelKit</artifactId>
    <version>2.0.72</version>
</dependency>
```

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

### User Entity with Annotation Mapping

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Defines the User entity and maps its fields to Excel columns using annotations. Supports custom validators, converters, and comments.

```java
@Excel("用户信息")
public class User {

  @ExcelField(value = "编号", width = 30)
  private Integer userId;

  @ExcelField(//
      value = "用户名",//
      required = true,//
      validator = UsernameValidator.class,//
      comment = "请填写用户名，最大长度为12，且不能重复"
  )
  private String username;

  @ExcelField(value = "密码", required = true, maxLength = 32)
  private String password;

  @ExcelField(value = "邮箱", validator = UserEmailValidator.class)
  private String email;

  @ExcelField(//
      value = "性别",//
      readConverterExp = "未知=0,男=1,女=2",//
      writeConverterExp = "0=未知,1=男,2=女",//
      options = SexOptions.class//
  )
  private Integer sex;

  @ExcelField(//
      value = "用户组",//
      name = "userGroup.name",//
      options = UserGroupNameOptions.class
  )
  private UserGroup userGroup;

  @ExcelField(value = "创建时间", dateFormat = "yyyy/MM/dd HH:mm:ss")
  private Date createAt;

  @ExcelField(//
      value = "自定义字段",//
      maxLength = 80,//
      comment = "可以乱填，但是长度不能超过80，导入时最终会转换为数字",//
      writeConverter = CustomizeFieldWriteConverter.class,// 写文件时，将数字转字符串
      readConverter = CustomizeFieldReadConverter.class// 读文件时，将字符串转数字
  )
  private Integer customizeField;
  
  // Getter and Setter ..
}
```

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

### Custom Cell Validation with Validator Interface

Source: https://github.com/wuwenze/excelkit/blob/master/README.md

Implement the Validator interface to define custom validation rules for cells during Excel import.

```java
public class UsernameValidator implements Validator {
  final List<String> ERROR_USERNAME_LIST = Lists.newArrayList(
      "admin", "root", "master", "administrator", "sb"
  );

  @Override
  public String valid(Object o) {
    String username = (String) o;
    if (username.length() > 12) {
      return "用户名不能超过12个字符。";
    }

    if (ERROR_USERNAME_LIST.contains(username)) {
      return "用户名非法，不允许使用。";
    }
    return null;
  }
}
```

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