Mybatis-Interceptor

先说一下我们要做的事情：在sql执行前对sql进行动态修改。
那拦截器到底如何设计才能做到修改sql呢，就要说到sqlSession的四大对象executor, statementHandler, parameterHandler，resultHandler。对于这四大对象有很多文章解析。

自定义拦截器

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@Signature声明要拦截的Executor对象中的query方法，如果方法不存在则会对该类所有方法进行拦截

/**
     * @param invocation Mybatis将动态代理对象封装而成
     * @return
     * @throws Throwable
     */
    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        Object[] args = invocation.getArgs();
        Executor executor = (Executor) invocation.getTarget();
        MappedStatement mappedStatement = (MappedStatement) args[0];
        Object parameter = args[1];
        RowBounds rowBounds = (RowBounds) args[2];
        ResultHandler resultHandler = (ResultHandler) args[3];
        CacheKey cacheKey = null;
        BoundSql boundSql = null;
        if (4 == args.length) {
            //拦截方法为4个参数时
            boundSql = mappedStatement.getBoundSql(parameter);
            cacheKey = executor.createCacheKey(mappedStatement, parameter, rowBounds, boundSql);
        } else {
            //拦截方法为6个参数时
            cacheKey = (CacheKey) args[4];
            boundSql = (BoundSql) args[5];
        }
        //逻辑判断，对sql做出处理等等
        if (1==1) {
            return executor.query(mappedStatement, parameter, RowBounds.DEFAULT, resultHandler, cacheKey, boundSql);
        }
        return executor.query(mappedStatement, parameter, rowBounds, resultHandler, cacheKey, boundSql);
    }

注册拦截器

 @Bean
    public DataInterceptor myBatisInterceptor() {
        return new DataInterceptor();
    }

最终Mybatis会将拦截器放入一个List中按照顺序执行