Mybatis的拦截器

Mybatis采用责任链模式，通过动态代理组织多个拦截器，通过这些拦截器可以改变Mybatis的默认行为。Mybatis的拦截器实现机制,使用的是JDK的InvocationHandler。

 

Mybatis对以下接口进行拦截：

       Executor

             是 Mybatis的内部执行器，它负责调用StatementHandler操作数据库，并把结果集通过 ResultSetHandler进行自动映射，另外，他还处理了二级缓存的操作。

             执行SQL语句，并且对事务、缓存等提供统一接口

 

       StatementHandler

              是Mybatis直接和数据库执行sql脚本的对象。另外它也实现了Mybatis的一级缓存。

              对 statement 进行预处理，并且提供统一的原子的增、删、改、查接口

 

       ResultSetHandler

              是Mybatis把ResultSet集合映射成POJO的接口对象。

              可以对Mybatis的结果集自动映射进行修改。

 

        PameterHandler

              是Mybatis实现Sql入参设置的对象。

 

注解类：

       @Intercepts：用于表明当前对象是一个Interceptor

       @Signature：表明要拦截的接口、方法以及对应的参数类型

 

自定义拦截器：

@Intercepts({
	@Signature(type=Executor.class, method="query"
			, args={MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}),
	@Signature(type=ResultSetHandler.class, method="handleResultSets", args={Statement.class}),
	@Signature(type=ParameterHandler.class, method="setParameters", args=PreparedStatement.class),
	@Signature(type=StatementHandler.class, method="prepare", args={Connection.class, Integer.class})
})
public class SeasyInterceptor implements Interceptor{
	@Override
	public Object intercept(Invocation invocation) throws Throwable {
		System.out.println(invocation.getMethod().getName());
		System.out.println(invocation.getTarget().getClass().getName());

		Object result = null;
		
		if(invocation.getTarget() instanceof ResultSetHandler){
			result = invocation.proceed();
			System.out.println("ResultSetHandler >> " + result.getClass().getName());
			
		}else if(invocation.getTarget() instanceof Executor){
	        System.out.println("Executor...");  
			result = invocation.proceed();
	        
		}else if(invocation.getTarget() instanceof ParameterHandler){
	        System.out.println("ParameterHandler...");  
	        
			ParameterHandler parameterHandler = (ParameterHandler) invocation.getTarget();
            PreparedStatement ps = (PreparedStatement) invocation.getArgs()[0];

            Field boundSqlField = parameterHandler.getClass().getDeclaredField("boundSql");
            boundSqlField.setAccessible(true);
            BoundSql boundSql = (BoundSql) boundSqlField.get(parameterHandler);
            String originalSql = boundSql.getSql();
			System.out.println(originalSql);
			
    		result = invocation.proceed();
    		
		}else if(invocation.getTarget() instanceof StatementHandler){
	        System.out.println("StatementHandler...");  
	        
			StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
			MetaObject metaStatementHandler = SystemMetaObject.forObject(statementHandler);
			BoundSql boundSql = (BoundSql) metaStatementHandler.getValue("delegate.boundSql");
			String originalSql = boundSql.getSql();
			System.out.println(originalSql);
			
			result = invocation.proceed();
			
		}else{
			result = invocation.proceed();
		}
		
        return result;
	}
	
	@Override
	public Object plugin(Object target) {
		return Plugin.wrap(target, this);
	}
	
	@Override
	public void setProperties(Properties properties) {
		String prop1 = properties.getProperty("prop1");
		System.out.println("prop1=" + prop1);
	}
}

 

Mybatis的配置类：

@Configuration
@EnableTransactionManagement  //开启注解式事务
@MapperScan("com.seasy.mybatis.mapper")
public class MybatisConfig implements TransactionManagementConfigurer{
	@Autowired
	DataSource dataSource;
    
    @Bean(name = "sqlSessionFactory")
    public SqlSessionFactory sqlSessionFactoryBean()throws Exception{
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(dataSource);
        
        //加载Mybatis的xml配置文件
    	PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        bean.setMapperLocations(resolver.getResources("classpath:mappers/*.xml"));
        
        //分页插件 PageHelper
        Properties prop = new Properties();
        prop.setProperty("offsetAsPageNum", "true");  
        prop.setProperty("rowBoundsWithCount", "true");  
        prop.setProperty("reasonable", "true");  
        prop.setProperty("dialect", "mysql");
        prop.setProperty("supportMethodsArguments", "true");
        prop.setProperty("returnPageInfo", "check");
        prop.setProperty("params", "count=countSql");

        PageHelper pageHelper = new PageHelper();
        pageHelper.setProperties(prop);

        Properties prop2 = new Properties();
        prop2.setProperty("prop1", "value1");
        
        SeasyInterceptor seasyInterceptor = new SeasyInterceptor();
        seasyInterceptor.setProperties(prop2);
        
        bean.setPlugins(new Interceptor[] { pageHelper, seasyInterceptor });
        
        return bean.getObject();
    }

    @Bean
    public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
        return new SqlSessionTemplate(sqlSessionFactory);
    }

    @Bean
    @Override
    public PlatformTransactionManager annotationDrivenTransactionManager() {
        return new DataSourceTransactionManager(dataSource);
    }
}