Struts的Action中获取Request和response对象

Struts2利用ServletActionContext维护Servlet对象，把Servlet对象放到了ServletActionContext中，

例如request、response、session、application

ServletActionContext利用ThreadLocal维护不同线程的Servlet对象，这种方式叫做非注入式（非IOC）。

不推荐使用这种方式，会存在线程不安全风险。

<span style="white-space:pre"></span>HttpServletRequest request = ServletActionContext.getRequest();HttpServletResponse response = ServletActionContext.getResponse();HttpSession session = request.getSession();ServletContext context = ServletActionContext.getServletContext();

2. 利用Aware接口：

 Struts2提供了Aware接口，Aware为”感知“的意思，实现了相关的Aware接口的Action能够感知相关的资源。在serveltConfig拦截器中，Struts2在实例化Action时，如果发现实现了相关的Aware接口，会把相关资源通过Aware注入进去。同时这种方式也是推荐的，因为可以保证线程安全。

3、看下ServletConfigInterceptor

/* * $Id$ * * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements.  See the NOTICE file * distributed with this work for additional information * regarding copyright ownership.  The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License.  You may obtain a copy of the License at * *  http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, * software distributed under the License is distributed on an * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * KIND, either express or implied.  See the License for the * specific language governing permissions and limitations * under the License. */package org.apache.struts2.interceptor;import java.util.Map;import javax.servlet.ServletContext;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.apache.struts2.StrutsStatics;import org.apache.struts2.servlet.interceptor.ServletPrincipalProxy;import org.apache.struts2.util.ServletContextAware;import com.opensymphony.xwork2.ActionContext;import com.opensymphony.xwork2.ActionInvocation;import com.opensymphony.xwork2.interceptor.AbstractInterceptor;/** * <!-- START SNIPPET: description --> * * An interceptor which sets action properties based on the interfaces an action implements. For example, if the action * implements {@link ParameterAware} then the action context's parameter map will be set on it. * * <p/> This interceptor is designed to set all properties an action needs if it's aware of servlet parameters, the * servlet context, the session, etc. Interfaces that it supports are: * * <ul> * * <li>{@link ServletContextAware}</li> * * <li>{@link ServletRequestAware}</li> * * <li>{@link ServletResponseAware}</li> * * <li>{@link ParameterAware}</li> * * <li>{@link RequestAware}</li> * * <li>{@link SessionAware}</li> * * <li>{@link ApplicationAware}</li> * * <li>{@link PrincipalAware}</li> * * </ul> * * <!-- END SNIPPET: description --> * * <p/> <u>Interceptor parameters:</u> * * <!-- START SNIPPET: parameters --> * * <ul> * * <li>None</li> * * </ul> * * <!-- END SNIPPET: parameters --> * * <p/> <u>Extending the interceptor:</u> * * <p/> * * <!-- START SNIPPET: extending --> * * There are no known extension points for this interceptor. * * <!-- END SNIPPET: extending --> * * <p/> <u>Example code:</u> * * <pre> * <!-- START SNIPPET: example --> * <action name="someAction" class="com.examples.SomeAction"> *     <interceptor-ref name="servletConfig"/> *     <interceptor-ref name="basicStack"/> *     <result name="success">good_result.ftl</result> * </action> * <!-- END SNIPPET: example --> * </pre> * * @see ServletContextAware * @see ServletRequestAware * @see ServletResponseAware * @see ParameterAware * @see SessionAware * @see ApplicationAware * @see PrincipalAware */public class ServletConfigInterceptor extends AbstractInterceptor implements StrutsStatics {    private static final long serialVersionUID = 605261777858676638L;    /**     * Sets action properties based on the interfaces an action implements. Things like application properties,     * parameters, session attributes, etc are set based on the implementing interface.     *     * @param invocation an encapsulation of the action execution state.     * @throws Exception if an error occurs when setting action properties.     */    public String intercept(ActionInvocation invocation) throws Exception {        final Object action = invocation.getAction();        final ActionContext context = invocation.getInvocationContext();        if (action instanceof ServletRequestAware) {            HttpServletRequest request = (HttpServletRequest) context.get(HTTP_REQUEST);            ((ServletRequestAware) action).setServletRequest(request);        }        if (action instanceof ServletResponseAware) {            HttpServletResponse response = (HttpServletResponse) context.get(HTTP_RESPONSE);            ((ServletResponseAware) action).setServletResponse(response);        }        if (action instanceof ParameterAware) {            ((ParameterAware) action).setParameters((Map)context.getParameters());        }        if (action instanceof ApplicationAware) {            ((ApplicationAware) action).setApplication(context.getApplication());        }                if (action instanceof SessionAware) {            ((SessionAware) action).setSession(context.getSession());        }                if (action instanceof RequestAware) {            ((RequestAware) action).setRequest((Map) context.get("request"));        }        if (action instanceof PrincipalAware) {            HttpServletRequest request = (HttpServletRequest) context.get(HTTP_REQUEST);            if(request != null) {                // We are in servtlet environment, so principal information resides in HttpServletRequest                ((PrincipalAware) action).setPrincipalProxy(new ServletPrincipalProxy(request));            }        }        if (action instanceof ServletContextAware) {            ServletContext servletContext = (ServletContext) context.get(SERVLET_CONTEXT);            ((ServletContextAware) action).setServletContext(servletContext);        }        return invocation.invoke();    }}

常用做法是：

定义一个baseAction，实现需要的Aware，让其他action继承此接口。

<span style="font-size:18px;">public BaseAction implements ServletContextAware, ServletRequestAware, ServletResponseAware, SessionAware @Overridepublic void setServletRequest(HttpServletRequest request) {try {request.setCharacterEncoding("UTF-8");} catch (UnsupportedEncodingException e) {e.printStackTrace();}}@Overridepublic void setServletResponse(HttpServletResponse response) {response.setCharacterEncoding("UTF-8");response.setContentType("text/html;charset=UTF-8");}@Overridepublic void setSession(Map<String, Object> session) {}@Overridepublic void setServletContext(ServletContext context) {this.context = context;}</span>