DefaultSqlSessionFactory

final Executor executor = configuration.newExecutor(tx, execType);
通过Configuration创建一个executor

Configuration

executor = (Executor) interceptorChain.pluginAll(executor);
动态代理executor （target）

InterceptorChain

=pluginAll(Object target) target是一个executor
for (Interceptor interceptor : interceptors/** 这个数组是插件的数组，所有插件都装到了这个数组*/) {
target = interceptor.plugin(target);一直生成，生成了一个又放进去生成，直到生成完毕，
}

interceptor（pagehelper）

@Intercepts(@Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}))
生成的代理类有一个signatureMap以type = Executor.class为key，其他method，args为value

@Override
public Object plugin(Object target) {
return Plugin.wrap(target, this);
}
Plugin.wrap(target, this)生成一个代理类

Plugin 插件接口

Plugin impl InvocationHandler
Plugin实现了InvocationHandler

=wrap()
生成代理类

if (interfaces.length > 0) {
  return Proxy.newProxyInstance(
      type.getClassLoader(),
      interfaces,
      new Plugin(target, interceptor, signatureMap));
}
return target;

=执行代理类
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
try {
Set methods = signatureMap.get(method.getDeclaringClass()); //mybatis就是通过signatureMap来判断是否要执行的
if (methods != null && methods.contains(method)) {
return interceptor.intercept(new Invocation(target, method, args));
}
return method.invoke(target, args);
} catch (Exception e) {
throw ExceptionUtil.unwrapThrowable(e);
}
}

return interceptor/** pageHelper*/.intercept(new Invocation(target, method, args));
走pagehelper的逻辑，

DefaultSqlSession

private Executor executor;
它里面有一个Executor，通过构造函数传进去。

List result = executor.query(ms, wrapCollection(parameter), rowBounds, Executor.NO_RESULT_HANDLER);
executor如果是有插件的话，这个executor已经是代理类了

Executor

有包含了一个plugin（Pagehelper）

List result = executor.query(ms, wrapCollection(parameter),
执行这一句，这里已经被它增强过了，走的是pagehelper的逻辑

也就是在生成executor的时候会生成插件代理

https://my.oschina.net/zudajun/blog/738973