Mybatis Plugin拦截器开发过程详解

这篇文章主要介绍了Mybatis Plugin拦截器开发过程详解,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下

1.Plugin

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)

注意;可以通过插件拦截到这四个对象，修改参数等操作：

你必须要知道的类:

org.apache.ibatis.plugin.Plugin org.apache.ibatis.reflection.SystemMetaObject

2.使用步骤

实现 Interceptor 接口

三个方法执行顺序

setProperties() plugin() intercept()

FirstIntercepter=====>setPropertiesFirstIntercepter====>pluginorg.apache.ibatis.executor.CachingExecutor@64485a47FirstIntercepter====>pluginorg.apache.ibatis.scripting.defaults.DefaultParameterHandler@2f0a87b3FirstIntercepter====>pluginorg.apache.ibatis.executor.resultset.DefaultResultSetHandler@4fcd19b3FirstIntercepter====>pluginorg.apache.ibatis.executor.statement.RoutingStatementHandler@2fd66ad3DEBUG 09-05 11:56:24,696 ==> Preparing: select * from employee where id=? (BaseJdbcLogger.java:159)FirstIntercepter:===>interceptDEBUG 09-05 11:56:24,722 ==> Parameters: 1(Integer) (BaseJdbcLogger.java:159)DEBUG 09-05 11:56:24,739 <== Total: 1 (BaseJdbcLogger.java:159)Employee [id=1, lastName=tom, gender=1, email=asd@qq.com, depid=null]

给你的拦截器签名：

/*** 完成插件签名：* 告诉MyBatis当前插件用来拦截哪个对象的哪个方法* type:要拦截的四大类型* method：拦截那个方法* args：这个方法的入参* */@Intercepts({@Signature(type=StatementHandler.class,method='parameterize',args=java.sql.Statement.class)})public class FirstIntercepter implements Interceptor

mybatis-cfg.xml中配置插件

这里注意配置plugins的标签顺序，以免出错，在environments上面

<!-- plugins 插件的配置 实际上是使用：intercepter原理代理的 --><plugins><plugin interceptor='mybatis.intercepter.FirstIntercepter'><property name='param1' value='root'/><property name='param2' value='root'/></plugin></plugins>

3.多个插件的执行

多个插件依次生成目标对象的代理对象，层层包裹，先声明的先包裹；形成代理链

可以理解为:初始化执行

执行log

FirstIntercepter=====>setProperties

MySecondIntercepter====>setProperties:{param1=root}FirstIntercepter====>pluginorg.apache.ibatis.executor.CachingExecutor@64485a47MySecondIntercepter====>plugin:org.apache.ibatis.executor.CachingExecutor@64485a47FirstIntercepter====>pluginorg.apache.ibatis.scripting.defaults.DefaultParameterHandler@2f0a87b3MySecondIntercepter====>plugin:org.apache.ibatis.scripting.defaults.DefaultParameterHandler@2f0a87b3FirstIntercepter====>pluginorg.apache.ibatis.executor.resultset.DefaultResultSetHandler@4fcd19b3MySecondIntercepter====>plugin:org.apache.ibatis.executor.resultset.DefaultResultSetHandler@4fcd19b3FirstIntercepter====>pluginorg.apache.ibatis.executor.statement.RoutingStatementHandler@2fd66ad3MySecondIntercepter====>plugin:org.apache.ibatis.executor.statement.RoutingStatementHandler@2fd66ad3DEBUG 09-05 12:07:01,928 ==> Preparing: select * from employee where id=? (BaseJdbcLogger.java:159)MySecondIntercepter====>intercept:public abstract void org.apache.ibatis.executor.statement.StatementHandler.parameterize(java.sql.Statement) throws java.sql.SQLExceptionFirstIntercepter:===>interceptDEBUG 09-05 12:07:01,954 ==> Parameters: 1(Integer) (BaseJdbcLogger.java:159)DEBUG 09-05 12:07:01,968 <== Total: 1 (BaseJdbcLogger.java:159)Employee [id=1, lastName=tom, gender=1, email=asd@qq.com, depid=null]

4.实现拦截修改参数

sql

<!-- Employee getSelectEmp(Integer id); --><select parameterType='java.lang.Integer'resultType='mybatis.bean.Employee'>select * from employee where id=#{id}</select>

这里我们拦截id：

由于ibatis中参数的声明存在与 StatementHandler中所以注意签名

@Intercepts({@Signature(type=StatementHandler.class,method='parameterize',args=java.sql.Statement.class)})

业务逻辑intercept方法中

/*** 1：业务逻辑处理的方法：*/@Overridepublic Object intercept(Invocation invocation) throws Throwable {//在这里可以进行业务逻辑修改System.out.println('FirstIntercepter:===>intercept'+invocation.getMethod()); MetaObject metaObject = SystemMetaObject.forObject(invocation.getTarget());//拿到target的元数据 StatementHandler==>ParameterHandler===>//DefaultParameterHandler==>>parameterObjectObject value = metaObject.getValue('parameterHandler.parameterObject');System.out.println('sql '+value.toString());//修改完sql语句要用的参数metaObject.setValue('parameterHandler.parameterObject', 2);Object object = invocation.proceed();return object;}

打印log，

可以看到原来入参为1，现在经过拦截器修改入参为2

DEBUG 09-05 12:36:23,387 ==> Preparing: select * from employee where id=? (BaseJdbcLogger.java:159)MySecondIntercepter====>intercept:public abstract void org.apache.ibatis.executor.statement.StatementHandler.parameterize(java.sql.Statement) throws java.sql.SQLExceptionFirstIntercepter:===>interceptpublic abstract void org.apache.ibatis.executor.statement.StatementHandler.parameterize(java.sql.Statement) throws java.sql.SQLExceptionsql 1DEBUG 09-05 12:36:23,418 ==> Parameters: 2(Integer) (BaseJdbcLogger.java:159)DEBUG 09-05 12:36:23,432 <== Total: 1 (BaseJdbcLogger.java:159)Employee [id=2, lastName=cat, gender=0, email=qwe@qq.com, depid=null]

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持好吧啦网。