Mybatis Plugin攔截器開發(fā)過程詳解

更新時(shí)間：2020年02月25日 12:17:30 作者：---WeiGeH

這篇文章主要介紹了Mybatis Plugin攔截器開發(fā)過程詳解,文中通過示例代碼介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值,需要的朋友可以參考下

1.Plugin

MyBatis 允許使用插件來(lái)攔截的方法調(diào)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(gè)對(duì)象，修改參數(shù)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(shí)現(xiàn) Interceptor 接口

三個(gè)方法執(zhí)行順序

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]

給你的攔截器簽名：

/**
* 完成插件簽名：
* 告訴MyBatis當(dāng)前插件用來(lái)攔截哪個(gè)對(duì)象的哪個(gè)方法
* type:要攔截的四大類型
* method：攔截那個(gè)方法
* args：這個(gè)方法的入?yún)?
* */
@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(biāo)簽順序，以免出錯(cuò)，在environments上面

<!-- plugins 插件的配置 實(shí)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(gè)插件的執(zhí)行

多個(gè)插件依次生成目標(biāo)對(duì)象的代理對(duì)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(zhí)行

執(zhí)行l(wèi)og

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.實(shí)現(xiàn)攔截修改參數(shù)

sql

<!-- Employee getSelectEmp(Integer id); -->
<select id="getSelectEmp" 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(shù)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(yè)務(wù)邏輯intercept方法中

/**
* 1：業(yè)務(wù)邏輯處理的方法：
*/
@Override
public Object intercept(Invocation invocation) throws Throwable {
//在這里可以進(jìn)行業(yè)務(wù)邏輯修改
System.out.println("FirstIntercepter:===>intercept"+invocation.getMethod());
 
MetaObject metaObject = SystemMetaObject.forObject(invocation.getTarget());
//拿到target的元數(shù)據(jù) StatementHandler==>ParameterHandler===>
//DefaultParameterHandler==>>parameterObject
Object value = metaObject.getValue("parameterHandler.parameterObject");
System.out.println("sql "+value.toString());
//修改完sql語(yǔ)句要用的參數(shù)
metaObject.setValue("parameterHandler.parameterObject", 2);
Object object = invocation.proceed();
return object;
}

打印log，

可以看到原來(lái)入?yún)?，現(xiàn)在經(jīng)過攔截器修改入?yún)?

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]

以上就是本文的全部?jī)?nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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