mybatis插件开发小例子

接上一节，我们继续实现小例子，比如说将查询id=1的员工改为查询id=3的员工：

MyFirstPlugin.java

package com.gong.mybatis.dao;

import java.util.Properties;

import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;


//完成插件签名，用于拦截哪个对象的哪个方法

@Intercepts({
    @Signature(type=StatementHandler.class,method="parameterize",args=java.sql.Statement.class)
})
public class MyFirstPlugin implements Interceptor {
    /**
     * intercept:拦截
     * */
    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        // TODO Auto-generated method stub
        System.out.println("myfirstplugin...intercept："+invocation.getMethod());
        Object target = invocation.getTarget();
        System.out.println("当前拦截到的对象："+target);
        MetaObject metaObject = SystemMetaObject.forObject(target);
        Object value = metaObject.getValue("parameterHandler.parameterObject");
        System.out.println("sql语句中的参数是："+value);
        metaObject.setValue("parameterHandler.parameterObject", 3);
        //执行目标方法
        Object proceed = invocation.proceed();
        //返回执行后的返回值
        return proceed;
    }
    
    //包装目标对象，为目标对象创建一个代理对象
    @Override
    public Object plugin(Object target) {
        System.out.println("-->myfirstplugin...plugin，将要包装的对象："+target);
        // TODO Auto-generated method stub
        Object wrap = Plugin.wrap(target, this);
        //返回为当前target创建的动态代理
        return wrap;
    }
    
    //将插件注册时的property属性设置进来
    @Override
    public void setProperties(Properties properties) {
        // TODO Auto-generated method stub
        System.out.println("插件配置的信息："+properties);
    }

}

注意橙色的代码，进行测试：

package com.gong.mybatis.test;

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

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 org.junit.Test;

import com.gong.mybatis.bean.Department;
import com.gong.mybatis.bean.Employee;
import com.gong.mybatis.dao.EmployeeMapper;
import com.gong.mybatis.mapper.EmployeeMapperDynamicSql;

public class TestMybatis5 {
    
    public SqlSessionFactory getSqlSessionFactory() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream is = Resources.getResourceAsStream(resource);
        return new SqlSessionFactoryBuilder().build(is);
    }

    @Test
    public void test() throws IOException {
        SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
        SqlSession openSession = sqlSessionFactory.openSession();
        
        try {
            EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
            Employee em = mapper.getEmpById(1);
            System.out.println(em);
        } finally {
            // TODO: handle finally clause
            openSession.close();
        }
    }
    
}

测试结果：

插件配置的信息：{password=123456, username=root}
-->myfirstplugin...plugin，将要包装的对象：
-->myfirstplugin...plugin，将要包装的对象：3da5
-->myfirstplugin...plugin，将要包装的对象：4973
-->myfirstplugin...plugin，将要包装的对象：65367
DEBUG 01-23 13:31:26,758 ==>  Preparing: select id,last_name lastName,email,gender from tbl_employee where id = ?   (BaseJdbcLogger.java:145) 
myfirstplugin...intercept：public abstract void org.apache.ibatis.executor.statement.StatementHandler.parameterize(java.sql.Statement) throws java.sql.SQLException
当前拦截到的对象：65367
sql语句中的参数是：1
DEBUG 01-23 13:31:26,837 ==> Parameters: 3(Integer)  (BaseJdbcLogger.java:145) 
DEBUG 01-23 13:31:26,866 <==      Total: 1  (BaseJdbcLogger.java:145) 
Employee [id=3, lastName=小红, gender=0, email, dept=null]