Mybatis 拦截器实现原理
作者:互联网
Mybatis 拦截器实现原理
标签(空格分隔): mybatis
拦截器概述
- 像springmvc一样,mybatis也提供了拦截器实现,只是他们拦截的对象不同。
- mybatis给Executor、StatementHandler、ResultSetHandler、ParameterHandler提供了拦截器功能,
- Executor提供了增删改查的接口.
- StatementHandler负责处理Mybatis与JDBC之间Statement的交互.
- ResultSetHandler负责处理Statement执行后产生的结果集,生成结果列表.
- ParameterHandler是Mybatis实现Sql入参设置的对象。
- 拦截器采用了责任链模式,把请求发送者和请求处理者分开,各司其职。
立即开始
<plugins>
<plugin interceptor="com.tamguo.demo.interceptor.StatementInterceptor"></plugin>
</plugins>
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class StatementInterceptor implements Interceptor {
public Object intercept(Invocation invocation) throws Throwable {
System.out.println(" hello Statement interceptor !");
return invocation.proceed();
}
public Object plugin(Object target) {
Object wrap = Plugin.wrap(target, this);
return wrap;
}
public void setProperties(Properties properties) {
}
}
开始一个Statement拦截器,在mybatis-config.xml加入plugin配置,编写一个StatementInterceptor类。这样就已经完成了一个拦截器的编写,该类会链接StatementHandler的prepare方法。
MyBatis 加载intercetor过程
pluginElement() 是Confiration中,解析XML并把interceptorInstance加入到interceptorChain。
private void pluginElement(XNode parent) throws Exception {
if (parent != null) {
for (XNode child : parent.getChildren()) {
String interceptor = child.getStringAttribute("interceptor");
Properties properties = child.getChildrenAsProperties();
Interceptor interceptorInstance = (Interceptor) resolveClass(interceptor).newInstance();
interceptorInstance.setProperties(properties);
configuration.addInterceptor(interceptorInstance);
}
}
}
到这里Confiration对象已经持有了一个InterceptorChain属性, InterceptorChain中只有一个intercetor的list集合。
sqlSessionFactory.openSession(),会创建Executor、StatementHandler、ResultSetHandler、ParameterHandler对象。
public Executor newExecutor(Transaction transaction, ExecutorType executorType) {
executorType = executorType == null ? defaultExecutorType : executorType;
executorType = executorType == null ? ExecutorType.SIMPLE : executorType;
Executor executor;
if (ExecutorType.BATCH == executorType) {
executor = new BatchExecutor(this, transaction);
} else if (ExecutorType.REUSE == executorType) {
executor = new ReuseExecutor(this, transaction);
} else {
executor = new SimpleExecutor(this, transaction);
}
if (cacheEnabled) {
executor = new CachingExecutor(executor);
}
executor = (Executor) interceptorChain.pluginAll(executor);
return executor;
}
executor = (Executor) interceptorChain.pluginAll(executor); 注意这一行代码,executor在这里已经被修改成一个代理对象。
标签:拦截器,StatementHandler,executorType,executor,Executor,Mybatis,原理,public 来源: https://www.cnblogs.com/tamguo/p/11231651.html