MyBatis插件开发的完整详细例子(附注释和总结)

import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.apache.ibatis.statement.StatementHandler;

import java.sql.Connection;
import java.sql.Statement;
import java.util.Properties;

@Intercepts({
    @Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}),
    @Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})
})
public class MyPlugin implements Interceptor {

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        // 获取被拦截方法的参数
        Object[] args = invocation.getArgs();

        // 拦截 Executor.query 方法
        if (invocation.getTarget() instanceof Executor) {
            MappedStatement ms = (MappedStatement) args[0];
            Object parameter = args[1];
            RowBounds rowBounds = (RowBounds) args[2];
            ResultHandler resultHandler = (ResultHandler) args[3];

            BoundSql boundSql = ms.getBoundSql(parameter);
            String sql = boundSql.getSql();
            System.out.println("Executing SQL: " + sql);

            // 执行原方法
            return invocation.proceed();
        }

        // 拦截 StatementHandler.prepare 方法
        if (invocation.getTarget() instanceof StatementHandler) {
            StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
            Connection connection = (Connection) args[0];
            Integer integer = (Integer) args[1];

            // 获取原始 SQL
            BoundSql boundSql = statementHandler.getBoundSql();
            String originalSql = boundSql.getSql();
            System.out.println("Original SQL: " + originalSql);

            // 修改 SQL（例如添加注释）
            String newSql = "/* MyPlugin */ " + originalSql;
            BoundSql newBoundSql = new BoundSql(
                boundSql.getMappedStatement().getConfiguration(),
                newSql,
                boundSql.getParameterMappings(),
                boundSql.getParameterObject()
            );
            MetaObject metaObject = SystemMetaObject.forObject(statementHandler);
            metaObject.setValue("delegate.boundSql", newBoundSql);

            // 执行原方法
            return invocation.proceed();
        }

        return invocation.proceed();
    }

    @Override
    public Object plugin(Object target) {
        // 使用 Plugin.wrap 包装目标对象
        return Plugin.wrap(target, this);
    }

    @Override
    public void setProperties(Properties properties) {
        // 设置插件属性（可选）
    }
}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- 配置插件 -->
    <plugins>
        <plugin interceptor="com.example.plugin.MyPlugin">
            <!-- 可以设置插件属性 -->
            <!-- <property name="propertyName" value="propertyValue"/> -->
        </plugin>
    </plugins>

    <!-- 其他配置... -->
</configuration>

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.Reader;

public class PluginTest {
    public static void main(String[] args) throws Exception {
        // 读取 MyBatis 配置文件
        Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);

        try (SqlSession session = sqlSessionFactory.openSession()) {
            UserMapper mapper = session.getMapper(UserMapper.class);

            // 执行查询操作，触发插件拦截
            User user = mapper.selectUserById(1L);
            System.out.println("User: " + user.getName());
        }
    }
}