Mybatis Plugin拦截器 Mybatis Plugin拦截器开发过程详解
---WeiGeH 人气:0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=====>setProperties FirstIntercepter====>pluginorg.apache.ibatis.executor.CachingExecutor@64485a47 FirstIntercepter====>pluginorg.apache.ibatis.scripting.defaults.DefaultParameterHandler@2f0a87b3 FirstIntercepter====>pluginorg.apache.ibatis.executor.resultset.DefaultResultSetHandler@4fcd19b3 FirstIntercepter====>pluginorg.apache.ibatis.executor.statement.RoutingStatementHandler@2fd66ad3 DEBUG 09-05 11:56:24,696 ==> Preparing: select * from employee where id=? (BaseJdbcLogger.java:159) FirstIntercepter:===>intercept DEBUG 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@64485a47 MySecondIntercepter====>plugin:org.apache.ibatis.executor.CachingExecutor@64485a47 FirstIntercepter====>pluginorg.apache.ibatis.scripting.defaults.DefaultParameterHandler@2f0a87b3 MySecondIntercepter====>plugin:org.apache.ibatis.scripting.defaults.DefaultParameterHandler@2f0a87b3 FirstIntercepter====>pluginorg.apache.ibatis.executor.resultset.DefaultResultSetHandler@4fcd19b3 MySecondIntercepter====>plugin:org.apache.ibatis.executor.resultset.DefaultResultSetHandler@4fcd19b3 FirstIntercepter====>pluginorg.apache.ibatis.executor.statement.RoutingStatementHandler@2fd66ad3 MySecondIntercepter====>plugin:org.apache.ibatis.executor.statement.RoutingStatementHandler@2fd66ad3 DEBUG 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.SQLException FirstIntercepter:===>intercept DEBUG 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 id="getSelectEmp" 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: */ @Override public 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==>>parameterObject Object 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.SQLException FirstIntercepter:===>interceptpublic abstract void org.apache.ibatis.executor.statement.StatementHandler.parameterize(java.sql.Statement) throws java.sql.SQLException sql 1 DEBUG 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]
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