Mybatis插件和批量操作

扩展一个简单的实现 

@Intercepts({
        @Signature(type = StatementHandler.class,method = "parameterize",args = java.sql.Statement.class)
})
public class MyFirstPlugin implements Interceptor {
    /**
     * intercept:拦截
     *      拦截目标对象的方法的执行
     * @param invocation
     * @return
     * @throws Throwable
     */
    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        System.out.println("MyFirstPlugin....interceptor:"+invocation.getMethod());

        //动态改变sql运行的参数：以前1号员工，现在4号

        Object target = invocation.getTarget();
        System.out.println("当前拦截对象："+target);
        //拿到StatementHandler====》ParameterHandler===》ParameterObject
        //拿到目标对象target的元数据
        MetaObject metaObject = SystemMetaObject.forObject(target);
        Object value = metaObject.getValue("parameterHandler.parameterObject");
        System.out.println("SQL语句用的参数是"+value);
        metaObject.setValue("parameterHandler.parameterObject",4);


        //执行目标方法
        Object proceed = invocation.proceed();
        //返回执行后的返回值
        return proceed;
    }

    /**
     * plugin:包装目标对象——包装：为目标对象创建一个代理类
     * @param target
     * @return
     */
    @Override
    public Object plugin(Object target) {
        System.out.println("MyFirstPlugin....plugin:mybatis将要包装的对象"+target);
        //我们可以借助Plugin的wrap方法来使用当前的intercept包装我们目标对象
        Object wrap = Plugin.wrap(target, this);
        //返回为当前target创建好的动态代理
        return wrap;
    }

    /**
     * setProperties:将插件注册时的property属性设置进来
     * @param properties
     */
    @Override
    public void setProperties(Properties properties) {
        System.out.println("插件配置的信息"+properties);
    }
}

@Test
public void testPlugin() throws IOException {
    SqlSession sqlSession = getSqlSession();
    EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);
    Employee e = mapper.getEmps(1);
    System.out.println(e);
}

分页插件pageHelper

配置依赖

    com.github.pagehelper
    pagehelper
    5.1.2

在全局配置文件中配置拦截器

    interceptor="com.github.pagehelper.PageInterceptor">

在代码中使用PageHelper.startPage( )即可实现分页

@Test
public void test() throws IOException {
    SqlSession sqlSession = getSqlSession();
    EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);

    PageHelper.startPage(1,5);

    List employeeList = mapper.getEmps();
    for (Employee e:employeeList) {
        System.out.println(employeeList);
    }
}

插件会自动查询数量和进行分页的sql

其他信息

@Test
public void test() throws IOException {
    SqlSession sqlSession = getSqlSession();
    EmployeeMapper mapper = sqlSession.getMapper(EmployeeMapper.class);

    Page