Strut2判斷是否為AJAX呼叫
1. AJAX與傳統Form表單
實際上，兩者一般都是透過HTTP的POST請求。差別是瀏覽器提交Form表單後，期望伺服器回傳一個完整的HTML頁面。而AJAX呼叫是由XMLHttpRequest物件（不同瀏覽器可能不一樣）發出，瀏覽器期望伺服器回傳HTML片段即可，具體是JSON、XML等都沒有要求。回到瀏覽器後如何使用，也是由JS腳本自己決定的。
2. 請求是不是AJAX
那麼對於伺服器端，如何判斷一個HTTP請求是不是AJAX呼叫？這需要看HTTP的Header。
我們可以透過Header中的x-request-with來判斷。儘管不同瀏覽器發送AJAX請求的物件不同，但是如果使用jQuery發送AJAX請求的話，jQuery內部實作ajax的時候，已經加入了標識。 jQuery原始碼中是這樣的：xhr.setRequestHeader("X-Requested-With","XMLHttpRequest");
所以，如果專案的前台頁面都是透過jQuery發送AJAX請求的話，這樣判斷是安全的。
下面是HTTP請求所攜帶的Header資訊。
普通Form表單提交
===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調用（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中獲得HTTP請求頭
在Action類中，通過ServletRequestAware接口獲得HttpServletRequest對象，再通過getHeader方法得到我們想要的頭資訊。
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性能調優攔截器
當我們在工作中需要實現某些小需求時，不妨先進行下簡單的調查，看看正在使用的開源框架是否已經了我們需要的功能，具備這樣就不用重複發明輪子了。
以下以效能測試為例，看看如何調查Struts2框架是否具備此功能。
1. struts-default.xml
因為Struts2的許多核心功能都是基於內部攔截器來實現的，所以我們首先要看看它是否有性能調優相關的攔截器。這就需要查看strut2-core-2.3.1.2.jar中的預設設定檔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像個百寶箱內建了許多攔截器，可以看到profiling很可能就是符合我們需求的攔截器，那現在就打開源碼一探究竟。
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();
}
}
<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>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");
}
}
});
}rrreee
列印結果就是下面如此。除了總執行時間外，Action方法的執行時間和Result的渲染時間都會分別列出。
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