Strut2判断是否是AJAX调用
1. AJAX与传统Form表单
实际上,两者一般都是通过HTTP的POST请求。区别是浏览器提交Form表单后,期望服务器返回一个完整的HTML页面。而AJAX调用是由XMLHttpRequest对象(不同浏览器可能不一样)发出,浏览器期望服务器返回HTML片段即可,具体是JSON、XML等都没有要求。返回到浏览器后如何使用,也是由JS脚本自己决定的。
2. 请求是不是AJAX
那么对于服务器端,如何判断一个HTTP请求是不是AJAX调用?这需要看HTTP的Header。
我们可以通过Header中的x-request-with来判断。尽管不同浏览器发送AJAX请求的对象不同,但是如果使用jQuery发送AJAX请求的话,jQuery内部实现ajax的时候,已经加入了标识。jQuery源码中是这样的:xhr.setRequestHeader("X-Requested-With","XMLHttpRequest");
所以,如果项目的前台页面都是通过jQuery发送AJAX请求的话,这样判断是安全的。
下面是HTTP请求携带的Header信息。
普通Form表单提交
===MimeHeaders === accept = */* referer =http://localhost:8080/user2/toQueryPage.action accept-language = zh-CN user-agent = Mozilla/4.0 (compatible; MSIE8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.3; .NET4.0C;.NET4.0E) accept-encoding = gzip, deflate host = localhost:8080 connection = Keep-Alive cache-control = no-cache
AJAX调用(IE)
===MimeHeaders === x-requested-with = XMLHttpRequest accept-language = zh-cn referer =http://localhost:8080/user2/toQueryPage.action accept = application/json, text/javascript,*/*; q=0.01 content-type =application/x-www-form-urlencoded accept-encoding = gzip, deflate user-agent = Mozilla/4.0 (compatible; MSIE8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.3; .NET4.0C;.NET4.0E) host = localhost:8080 content-length = 57 connection = Keep-Alive cache-control = no-cache
3. 在Action中获得HTTP请求头
在Action类中,通过ServletRequestAware接口获得HttpServletRequest对象,再通过getHeader方法得到我们想要的头信息。
public abstract class BaseAction <ParamVo extends BaseParamVo, ResultVo extends BaseResultVo> extends ActionSupport implements ServletRequestAware { private static final String AJAX_RESULT_NAME = "ajaxResult"; private static final String XHR_OBJECT_NAME = "XMLHttpRequest"; private static final String HEADER_REQUEST_WITH = "x-requested-with"; /** * Request对象,用来判断请求是否是AJAX调用 */ private HttpServletRequest request; private ParamVo paramVo; private ResultVo resultVo; @Override public String execute() { String resultPage = SUCCESS; try { resultVo = doExecute(paramVo); } catch (BaseException e) { resultPage = ERROR; } if (XHR_OBJECT_NAME.equals(request.getHeader(HEADER_REQUEST_WITH))) { resultPage = AJAX_RESULT_NAME; } return resultPage; } }
Struts2性能调优拦截器
当我们在工作中需要实现某些小需求时,不妨先进行下简单的调研,看看正在使用的开源框架是否已经具备了我们需要的功能,这样就不用重复发明轮子了。
下面以性能测试为例,看看如何调查Struts2框架是否具备这种功能。
1. struts-default.xml
因为Struts2的许多核心功能都是基于内部拦截器来实现的,所以我们首先要看看它是否有性能调优相关的拦截器。这就需要查看strut2-core-2.3.1.2.jar中的默认配置文件struts-default.xml了。
<span style="white-space:pre"> </span><interceptor name="alias" class="com.opensymphony.xwork2.interceptor.AliasInterceptor"/> <interceptor name="autowiring" class="com.opensymphony.xwork2.spring.interceptor.ActionAutowiringInterceptor"/> <interceptor name="chain" class="com.opensymphony.xwork2.interceptor.ChainingInterceptor"/> <interceptor name="conversionError" class="org.apache.struts2.interceptor.StrutsConversionErrorInterceptor"/> <interceptor name="cookie" class="org.apache.struts2.interceptor.CookieInterceptor"/> <interceptor name="clearSession" class="org.apache.struts2.interceptor.ClearSessionInterceptor" /> <interceptor name="createSession" class="org.apache.struts2.interceptor.CreateSessionInterceptor" /> <interceptor name="debugging" class="org.apache.struts2.interceptor.debugging.DebuggingInterceptor" /> <interceptor name="execAndWait" class="org.apache.struts2.interceptor.ExecuteAndWaitInterceptor"/> <interceptornameinterceptorname="exception" class="com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor"/> <interceptor name="fileUpload" class="org.apache.struts2.interceptor.FileUploadInterceptor"/> <interceptor name="i18n" class="com.opensymphony.xwork2.interceptor.I18nInterceptor"/> <interceptor name="logger" class="com.opensymphony.xwork2.interceptor.LoggingInterceptor"/> <interceptor name="modelDriven" class="com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor"/> <interceptor name="scopedModelDriven" class="com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor"/> <interceptor name="params" class="com.opensymphony.xwork2.interceptor.ParametersInterceptor"/> <interceptor name="actionMappingParams" class="org.apache.struts2.interceptor.ActionMappingParametersInteceptor"/> <interceptor name="prepare" class="com.opensymphony.xwork2.interceptor.PrepareInterceptor"/> <interceptor name="staticParams" class="com.opensymphony.xwork2.interceptor.StaticParametersInterceptor"/> <interceptor name="scope" class="org.apache.struts2.interceptor.ScopeInterceptor"/> <interceptor name="servletConfig" class="org.apache.struts2.interceptor.ServletConfigInterceptor"/> <interceptor name="timer" class="com.opensymphony.xwork2.interceptor.TimerInterceptor"/> <interceptor name="token" class="org.apache.struts2.interceptor.TokenInterceptor"/> <interceptor name="tokenSession" class="org.apache.struts2.interceptor.TokenSessionStoreInterceptor"/> <interceptor name="validation" class="org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor"/> <interceptor name="workflow" class="com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor"/> <interceptor name="store" class="org.apache.struts2.interceptor.MessageStoreInterceptor" /> <interceptor name="checkbox" class="org.apache.struts2.interceptor.CheckboxInterceptor" /> <interceptor name="profiling" class="org.apache.struts2.interceptor.ProfilingActivationInterceptor" /> <interceptor name="roles" class="org.apache.struts2.interceptor.RolesInterceptor" /> <interceptor name="annotationWorkflow" class="com.opensymphony.xwork2.interceptor.annotations.AnnotationWorkflowInterceptor" /> <interceptor name="multiselect" class="org.apache.struts2.interceptor.MultiselectInterceptor" />
Struts2像个百宝箱一样内置了很多拦截器,可以看到profiling很可能就是符合我们需求的拦截器,那现在就打开源码一探究竟。
2. ProfilingActivationInterceptor
org.apache.struts2.interceptor.ProfilingActivationInterceptor.java
public class ProfilingActivationInterceptor extendsAbstractInterceptor { private String profilingKey = "profiling"; private boolean devMode; @Inject(StrutsConstants.STRUTS_DEVMODE) public void setDevMode(String mode) { this.devMode = "true".equals(mode); } @Override public String intercept(ActionInvocationinvocation) throws Exception { if (devMode) { Object val =invocation.getInvocationContext().getParameters().get(profilingKey); if (val != null) { String sval = (val instanceof String ?(String)val : ((String[])val)[0]); boolean enable = "yes".equalsIgnoreCase(sval)|| "true".equalsIgnoreCase(sval); UtilTimerStack.setActive(enable); invocation.getInvocationContext().getParameters().remove(profilingKey); } } return invocation.invoke(); } }
从源码中可以看到,只要浏览器发过来的HTTP请求参数中包含profiling=true或者yes,性能拦截器就会开启Timer工具类,打印出Action的执行消耗时间。
3. struts.xml
因为profiling拦截器没有包含到默认的defaultStack中,所以我们要先将它追加到我们自定义的拦截器栈中。
<package name="ajax-default" extends="velocity-default"> <result-types> <result-type name="json" class="org.apache.struts2.json.JSONResult"/> </result-types> <interceptors> <interceptor-stacknameinterceptor-stackname="ajaxInterceptorStack"> <interceptor-refnameinterceptor-refname="defaultStack" /> <interceptor-ref name="profiling"/> </interceptor-stack> </interceptors> <default-interceptor-refnamedefault-interceptor-refname="ajaxInterceptorStack" /> <global-results> <result name="comAjaxResult" type="json"> <param name="excludeNullProperties">true</param> <param name="root">result</param> <param name="ignoreHierarchy">false</param> </result> </global-results> </package>
4. userview.js
现在就可以修改AJAX调用参数,追加上profiling参数就可以开始性能调优了。
function searchAllUser(){ jQuery.ajax({ type:"post", url: "searchAllUser.action", processData:true, dataType:'json', data:jQuery("#userQueryForm").serialize() + "&profiling=yes", success:function(data) { if (data.status == 1) { alert("创建成功"); generateTableFromJson("result", data.resultRows); } else { alert("创建失败"); } } }); }
5. 最终效果
打印结果就是下面这样。除了总执行时间外,Action方法的执行时间和Result的渲染时间都会分别列出。
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