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