mybatis的插件机制示例详解

 public ParameterHandler newParameterHandler(MappedStatement mappedStatement, Object object, BoundSql sql, InterceptorChain interceptorChain){
 ParameterHandler parameterHandler = mappedStatement.getLang().createParameterHandler(mappedStatement,object,sql);
 parameterHandler = (ParameterHandler) interceptorChain.pluginAll(parameterHandler);
 return parameterHandler;
 }
public Object pluginAll(Object target) {
 for (Interceptor interceptor : interceptors) {
 target = interceptor.plugin(target);
 }
 return target;
 }

/** 插件签名，告诉mybatis单钱插件用来拦截那个对象的哪个方法 **/
@Intercepts({@Signature(type = ResultSetHandler.class,method ="handleResultSets",args = Statement.class)})
public class MyFirstInterceptor implements Interceptor {

 /** @Description 拦截目标对象的目标方法 **/
 @Override
 public Object intercept(Invocation invocation) throws Throwable {
 System.out.println("拦截的目标对象："+invocation.getTarget());
 Object object = invocation.proceed();
 return object;
 }
 /**
 * @Description 包装目标对象 为目标对象创建代理对象
 * @Param target为要拦截的对象
 * @Return 代理对象
 */
 @Override
 public Object plugin(Object target) {
 System.out.println("将要包装的目标对象："+target);
 return Plugin.wrap(target,this);
 }
 /** 获取配置文件的属性 **/
 @Override
 public void setProperties(Properties properties) {
 System.out.println("插件配置的初始化参数："+properties);
 }
}

<!-- 自定义插件 -->
 <plugins>
  <plugin interceptor="mybatis.interceptor.MyFirstInterceptor">
   <!--配置参数-->
   <property name="name" value="Bob"/>
  </plugin>
 </plugins>

public class MyBatisTest {
 public static SqlSessionFactory sqlSessionFactory = null;

 public static SqlSessionFactory getSqlSessionFactory() {
  if (sqlSessionFactory == null) {
   String resource = "mybatis-config.xml";
   try {
    Reader reader = Resources.getResourceAsReader(resource);
    sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
   } catch (IOException e) {
    e.printStackTrace();
   }
  }
  return sqlSessionFactory;
 }

 public void testGetById()
 {
  SqlSession sqlSession = this.getSqlSessionFactory().openSession();
  PersonMapper personMapper = sqlSession.getMapper(PersonMapper.class);
  Person person=personMapper.getById(2001);
  System.out.println(person.toString());
 }

public static void main(String[] args) {
  new MyBatisTest().testGetById();
 }
}