Mybatis Plugin攔截器開發過程詳解

這篇文章主要介紹了Mybatis Plugin攔截器開發過程詳解,文中通過示例代碼介紹的非常詳細，對大家的學習或者工作具有一定的參考學習價值,需要的朋友可以參考下

1.Plugin

MyBatis 允許使用插件來攔截的方法調用包括：

• Executor (update, query, flushStatements, commit, rollback,getTransaction, close, isClosed) • ParameterHandler (getParameterObject, setParameters) • ResultSetHandler (handleResultSets, handleOutputParameters) • StatementHandler (prepare, parameterize, batch, update, query)

注意;可以通過插件攔截到這四個對象，修改參數等操作：

你必須要知道的類:

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

2.使用步驟

實現 Interceptor 接口

三個方法執行順序

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]

給你的攔截器簽名：

/*** 完成插件簽名：* 告訴MyBatis當前插件用來攔截哪個對象的哪個方法* type:要攔截的四大類型* method：攔截那個方法* args：這個方法的入參* */@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

這里注意配置plugins的標簽順序，以免出錯，在environments上面

<!-- plugins 插件的配置 實際上是使用：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.多個插件的執行

多個插件依次生成目標對象的代理對象，層層包裹，先聲明的先包裹；形成代理鏈

可以理解為:初始化執行

執行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.實現攔截修改參數

sql

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

這里我們攔截id：

由于ibatis中參數的聲明存在與 StatementHandler中所以注意簽名

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

業務邏輯intercept方法中

/*** 1：業務邏輯處理的方法：*/@Overridepublic Object intercept(Invocation invocation) throws Throwable {//在這里可以進行業務邏輯修改System.out.println('FirstIntercepter:===>intercept'+invocation.getMethod()); MetaObject metaObject = SystemMetaObject.forObject(invocation.getTarget());//拿到target的元數據 StatementHandler==>ParameterHandler===>//DefaultParameterHandler==>>parameterObjectObject value = metaObject.getValue('parameterHandler.parameterObject');System.out.println('sql '+value.toString());//修改完sql語句要用的參數metaObject.setValue('parameterHandler.parameterObject', 2);Object object = invocation.proceed();return object;}

打印log，

可以看到原來入參為1，現在經過攔截器修改入參為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內容，希望對大家的學習有所幫助，也希望大家多多支持好吧啦網。