Springboot的Mybatis拦截器实现[通俗易懂]

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MyBatis提供了一种插件(plugin)的功能，虽然叫做插件，其实就是拦截器功能

MyBatis 允许拦截的接口

MyBatis 允许你在已映射语句执行过程中的某一点进行拦截调用。默认情况下，MyBatis 允许使用插件来拦截的方法调用包括：

Executor (update, query, flushStatements, commit, rollback, getTransaction, close, isClosed)

ParameterHandler (getParameterObject, setParameters)

ResultSetHandler (handleResultSets, handleOutputParameters)

StatementHandler (prepare, parameterize, batch, update, query)

Executor接口的部分方法，比如update，query，commit，rollback等方法，还有其他接口的一些方法等。

总体概括为：

拦截执行器的方法
拦截参数的处理
拦截结果集的处理,为sql执行之后的结果拦截过滤
拦截Sql语法构建的处理,为sql执行之前的拦截进行sql封装

MyBatis拦截器的接口定义

一共有三个方法intercept 、plugin 、setProperties

`setProperties()`

方法主要是用来从配置中获取属性。

如果是使用xml式配置拦截器，可在Mybatis配置文件中添加如下节点，属性可以以如下方式传递

<plugins>
	<plugin interceptor="tk.mybatis.simple.plugin.XXXInterceptor">
		<property name="propl" value="valuel" />
		<property name="prop2" value="value2" />
	</plugin>
</plugins>

如果在Spring boot中使用，则需要单独写一个配置类，如下：

@Configuration
public class MybatisInterceptorConfig { 
   
    @Bean
    public String myInterceptor(SqlSessionFactory sqlSessionFactory) { 
   
        ExecutorInterceptor executorInterceptor = new ExecutorInterceptor();
        Properties properties = new Properties();
        properties.setProperty("prop1","value1");
        executorInterceptor.setProperties(properties);
        return "interceptor";
    }
}

如果说不需要配置属性，则在spring boot中，不需要去编写配置类，只需要像我一样在拦截器上加个@Component即可。

`plugin()`

方法用于指定哪些方法可以被此拦截器拦截。

`intercept()`

方法是用来对拦截的sql进行具体的操作。

注解实现

MyBatis拦截器用到了两个注解：@Intercepts和@Signature

@Intercepts(
        { 
   
                @Signature(type = Executor.class, method = "query",
                        args = { 
   MappedStatement.class, Object.class,
                                RowBounds.class, ResultHandler.class}),
                @Signature(type = Executor.class, method = "query",
                        args = { 
   MappedStatement.class, Object.class, RowBounds.class,
                                ResultHandler.class, CacheKey.class, BoundSql.class}),
        }
)

type的值与类名相同，method与方法名相同，为了避免方法重载，args中指定了各个参数的类型和个数，可通过invocation.getArgs()获取参数数组。

Executor 拦截器实现

@Intercepts({ 
   
        @Signature(
        type= Executor.class,
        method = "query",
        args = { 
   MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}
        )
})
@Slf4j
@Component
public class ExecutorInterceptor implements Interceptor { 
   
    @Override
    public Object intercept(Invocation invocation) throws Throwable { 
   
        String sql = ExecutorPluginUtils.getSqlByInvocation(invocation);
        //可以对sql重写
        log.error("拦截器ExecutorInterceptor:"+sql);
        //sql = "SELECT id from BUS_RECEIVER where id = ? ";
        ExecutorPluginUtils.resetSql2Invocation( invocation,  sql);
        return invocation.proceed();
    }

    @Override
    public Object plugin(Object o) { 
   
        return Plugin.wrap(o, this);
    }

    @Override
    public void setProperties(Properties properties) { 
   

    }


}

ParameterHandler 拦截器实现

/** * @Author: ynz * @Date: 2018/12/23/023 12:07 */
@Intercepts({ 
   
        @Signature(type = ParameterHandler.class, method = "setParameters", args = PreparedStatement.class),
})
@Component
@Slf4j
public class ParamInterceptor  implements Interceptor { 
   

    @Override
    public Object intercept(Invocation invocation) throws Throwable { 
   

        log.error("拦截器ParamInterceptor");
        //拦截 ParameterHandler 的 setParameters 方法 动态设置参数
        if (invocation.getTarget() instanceof ParameterHandler) { 
   
            ParameterHandler parameterHandler = (ParameterHandler) invocation.getTarget();
            PreparedStatement ps = (PreparedStatement) invocation.getArgs()[0];

            // 反射获取 BoundSql 对象，此对象包含生成的sql和sql的参数map映射
            Field boundSqlField = parameterHandler.getClass().getDeclaredField("boundSql");
            boundSqlField.setAccessible(true);
            BoundSql boundSql = (BoundSql) boundSqlField.get(parameterHandler);
            // 反射获取 参数对像
            Field parameterField = 
                    parameterHandler.getClass().getDeclaredField("parameterObject");
            parameterField.setAccessible(true);
            Object parameterObject = parameterField.get(parameterHandler);

            if (parameterObject instanceof Map) { 
   
                //将参数中的name值改为2
                ((Map) parameterObject).put("name","2");
            }

            // 改写的参数设置到原parameterHandler对象
            parameterField.set(parameterHandler, parameterObject);
            parameterHandler.setParameters(ps);


            log.error(JSON.toJSONString(boundSql.getParameterMappings()));
            log.error(JSON.toJSONString(parameterObject));
        }
        return invocation.proceed();
    }

    @Override
    public Object plugin(Object o) { 
   
        return Plugin.wrap(o, this);
    }

    @Override
    public void setProperties(Properties properties) { 
   

    }
}

ResultSetHandler 拦截器实现

@Intercepts({ 
   
        @Signature(type = ResultSetHandler.class, method = "handleResultSets", args={ 
   Statement.class})
})
@Component
@Slf4j
public class ResultInterceptor implements Interceptor { 
   

    @Override
    public Object intercept(Invocation invocation) throws Throwable { 
   
        log.error("拦截器ResultInterceptor");
       // ResultSetHandler resultSetHandler1 = (ResultSetHandler) invocation.getTarget();
        //通过java反射获得mappedStatement属性值
        //可以获得mybatis里的resultype
        Object result = invocation.proceed();
        if (result instanceof ArrayList) { 
   
            ArrayList resultList = (ArrayList) result;
            for (int i = 0; i < resultList.size(); i++) { 
   
                Object oi = resultList.get(i);
                Class c = oi.getClass();
                Class[] types = { 
   String.class};
                Method method = c.getMethod("setAddress", types);
                // 调用obj对象的 method 方法
                method.invoke(oi, "china");
            }
        }
        return result;
    }

    @Override
    public Object plugin(Object target) { 
   
        return Plugin.wrap(target, this);
    }

    @Override
    public void setProperties(Properties properties) { 
   

    }
}

StatementHandler 拦截器实现

/** * @Author: ynz * @Date: 2018/12/23/023 14:22 */
@Intercepts(
        { 
   @Signature(
                type = StatementHandler.class,
                method = "prepare",
                args = { 
   Connection.class, Integer.class}
                )
        })
@Component
@Slf4j
public class StatementInterceptor implements Interceptor { 
   

    @Override
    public Object intercept(Invocation invocation) throws Throwable { 
   
        StatementHandler statementHandler = 
                (StatementHandler) PluginUtils.realTarget(invocation.getTarget());
        MetaObject metaStatementHandler = SystemMetaObject.forObject(statementHandler);
        MappedStatement mappedStatement = 
                (MappedStatement) metaStatementHandler.getValue("delegate.mappedStatement");
        //只拦截select方法
        if (!SqlCommandType.SELECT.equals(mappedStatement.getSqlCommandType())) { 
   
            return invocation.proceed();
        }
        BoundSql boundSql = (BoundSql) metaStatementHandler.getValue("delegate.boundSql");
        //获取到sql
        String originalSql = boundSql.getSql();
        //可以对originalSql进行改写
        log.error("拦截器StatementInterceptor:"+originalSql);
        metaStatementHandler.setValue("delegate.boundSql.sql", originalSql);
        Object parameterObject = boundSql.getParameterObject();
        return invocation.proceed();
    }

    @Override
    public Object plugin(Object target) { 
   
        return Plugin.wrap(target, this);
    }

    @Override
    public void setProperties(Properties properties) { 
   

    }
}

Spring Boot整合

方法1：手写一个配置类

@Configuration
public class MybatisInterceptorConfig { 
   
    @Bean
    public String myInterceptor(SqlSessionFactory sqlSessionFactory) { 
   
        ExecutorInterceptor executorInterceptor = new ExecutorInterceptor();
        Properties properties = new Properties();
        properties.setProperty("prop1","value1");
        executorInterceptor.setProperties(properties);
        sqlSessionFactory.getConfiguration().addInterceptor(executorInterceptor);
        sqlSessionFactory.getConfiguration().addInterceptor(new ParamInterceptor());
        sqlSessionFactory.getConfiguration().addInterceptor(new ResultInterceptor());
        return "interceptor";
    }
}

方法2：在拦截器上加`@Component`注解

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Springboot的Mybatis拦截器实现[通俗易懂]

MyBatis提供了一种插件(plugin)的功能，虽然叫做插件，其实就是拦截器功能

MyBatis 允许拦截的接口

MyBatis拦截器的接口定义

setProperties()

plugin()

intercept()

注解实现

Executor 拦截器实现

ParameterHandler 拦截器实现

ResultSetHandler 拦截器实现

StatementHandler 拦截器实现

Spring Boot整合

方法1：手写一个配置类

方法2：在拦截器上加@Component注解

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发表回复

`setProperties()`

`plugin()`

`intercept()`

方法2：在拦截器上加`@Component`注解