详解Spring Controller autowired Request变量

详解spring controller autowired request变量

spring的di大家比较熟悉了，对于依赖注入的实现也无须赘述。

那么spring的bean的默认scope为singleton，对于controller来说每次方法中均可以获得request还是比较有意思的。

对于方法参数上的request通过构建方法的参数可以获得最新的request

public final object invokeforrequest(nativewebrequest request, modelandviewcontainer mavcontainer,
   object... providedargs) throws exception {
 
  object[] args = getmethodargumentvalues(request, mavcontainer, providedargs);
  if (logger.istraceenabled()) {
   stringbuilder sb = new stringbuilder("invoking [");
   sb.append(getbeantype().getsimplename()).append(".");
   sb.append(getmethod().getname()).append("] method with arguments ");
   sb.append(arrays.aslist(args));
   logger.trace(sb.tostring());
  }
  object returnvalue = invoke(args);
  if (logger.istraceenabled()) {
   logger.trace("method [" + getmethod().getname() + "] returned [" + returnvalue + "]");
  }
  return returnvalue;
}

2. 对于controller等单实例变量来说如何动态注入变量呢？spring使用了很聪明的办法

1. 首先request和用户请求相关
2. 不同的用户同时访问时是在不同的线程中
3. 保存了用户的请求在threadlocal中
4. 用户获取该请求需要手动调用threadlocal来获取
5. 为了帮助用户减少重复代码，spring可以让用户‘动态'注入request
6. 当controller在实例化时，动态注册一个proxy到当前request变量中
7. 此proxy当被使用是可以将所有方法动态路由到threadlocal中该request变量上执行

/**
 * register web-specific scopes ("request", "session", "globalsession", "application")
 * with the given beanfactory, as used by the webapplicationcontext.
 * @param beanfactory the beanfactory to configure
 * @param sc the servletcontext that we're running within
 */
public static void registerwebapplicationscopes(configurablelistablebeanfactory beanfactory, servletcontext sc) {
  beanfactory.registerscope(webapplicationcontext.scope_request, new requestscope());
  beanfactory.registerscope(webapplicationcontext.scope_session, new sessionscope(false));
  beanfactory.registerscope(webapplicationcontext.scope_global_session, new sessionscope(true));
  if (sc != null) {
   servletcontextscope appscope = new servletcontextscope(sc);
   beanfactory.registerscope(webapplicationcontext.scope_application, appscope);
   // register as servletcontext attribute, for contextcleanuplistener to detect it.
   sc.setattribute(servletcontextscope.class.getname(), appscope);
  }
 
  beanfactory.registerresolvabledependency(servletrequest.class, new requestobjectfactory());
  beanfactory.registerresolvabledependency(httpsession.class, new sessionobjectfactory());
  beanfactory.registerresolvabledependency(webrequest.class, new webrequestobjectfactory());
  if (jsfpresent) {
   facesdependencyregistrar.registerfacesdependencies(beanfactory);
  }
}


 

 

 /**
 * factory that exposes the current request object on demand.
 */
 @suppresswarnings("serial")
 private static class requestobjectfactory implements objectfactory<servletrequest>, serializable {

 public servletrequest getobject() {
  return currentrequestattributes().getrequest();
 }

 @override
 public string tostring() {
  return "current httpservletrequest";
 }
 }
 

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