如何使用Struts 2中的超链接传递操作名称？ [英] How to pass a action name using hyperlink in Struts 2?

问题描述

我有一个名为的超链接点击新用户。点击链接后，我得到 NullPointerException ，而不是打开 RegisterPage.jsp 页面。

I have a hyperlink named "Click for new User". Once I click the link, I got NullPointerException instead of opening RegisterPage.jsp page.

我在这里发布我的代码，我找不到我的错误

I post my code here, I can't find my mistake

index.jsp ：

index.jsp:

<s:form action="verify">
<s:textfield name="username" key="label.uname"  required="true"/>
<s:password name="password" key="label.pass" required="true"/>
<s:submit value="Login" align="center"/> 
</s:form>
<a href="<s:url action='register'/>">Click for New User</a>

struts.xml ：

struts.xml:

<struts>
<package name="a" extends="struts-default">
<action name="verify" class="java4s.Login"  method="execute">
<result name="success">loginsuccess.jsp</result>
<result name="error">error.jsp</result>
<result name="input">index.jsp</result>
</action>
<action name="register" class="java4s.Login" method="register">
<result name="success">RegisterPage.jsp</result>
</action>
</package>
</struts>

Login.java （行动类）：

Login.java(Action Class):

package java4s;

import com.opensymphony.xwork2.ActionSupport;

public class Login extends ActionSupport {

private static final long serialVersionUID = 1L;
private String username,password;
public String getUsername() {
    return username;
}
public void setUsername(String username) {
    this.username = username;
}
public String getPassword() {
    return password;
}
public void setPassword(String password) {
    this.password = password;
}
public String register(){
    System.out.println("register ()");
    return SUCCESS;
}
public String execute(){
    if (getUsername().equals("java4s")&&getPassword().equals("java4s")) {
        return SUCCESS;
    } else {
        this.addActionError(getText("u.p.wrong"));
        return ERROR;
    }   
}
@Override
public void validate() {
        if (getUsername().equals("")||getUsername().length()==0)
        this.addFieldError("username",getText("error.uname"));
        if(getPassword().equals("")||getPassword().length()==0) 
        this.addFieldError("password", getText("error.pass"));

}
}

异常：

 javax.servlet.ServletException: java.lang.NullPointerException
 org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:515)
 org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:4‌​19)
 java.lang.NullPointerException
java4s.Login.validate(Login.java:38)
com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:200)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:150)
org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:48)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:123)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:167)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:105)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:83)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:207)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:74)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:127)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
org.apache.struts2.interceptor.ProfilingActivationInterceptor.intercept(ProfilingActivationInterceptor.java:107)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:206)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:115)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:143)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:121)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:170)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:123)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:176) 
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)
org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:50)
org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:504)
org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:419)

推荐答案

点击在超链接上，您不提供带参数用户名和密码的请求URL（参数不是由 params interceptor），因此这些属性的值为 null ，但有效在执行操作之前调用ate（）方法，因为您的操作扩展 ActionSupport 实现了 Validateable 和 ValidationAware 允许验证拦截器（它是 defaultStack <的一部分/ code>）执行 validate（）方法，您可以在其中执行手动检查并提供 ActionErrors ， FieldErrors 和 ActionMessages 。但如果您不提供属性的值，则没有理由这样做。您应该提交表单或在网址中设置参数，如

When you click on hyperlink you don't supply the request URL with parameters username and password (the parameters aren't set by the params interceptor), so the values of this properties are null but the validate() method is called before the action is executed because your action extend ActionSupport which implemented Validateable and ValidationAware that allows the validation interceptor (which is a part of the defaultStack) execute validate() method where you could perform manual checks and provide ActionErrors, FieldErrors, and ActionMessages. But there's no reason to do so if you don't provide the values for the properties. You should either submit the form or set the parameters in the url like

<a id="myLink" href="#">Click for New User</a>
<script type="text/javascript>
$(document).ready(function(){
  $('#myLink').click(function(e) {
    window.location="<s:url action='register'/>"+"?username="+$('username').val()+"&password="+$('password').val();
    return false;
  });
});
</script>

但问题是参数值（用户名和密码）是敏感信息，不应传入URL。你应该使用Ajax 发布或提交带有 POST 请求的表单，如这个示例。

But the problem is the parameter values (username and password) are sensitive information and shouldn't pass in the URL. And you should use either Ajax post or submit the form with the POST request like in this example.

非常使用手动验证时有用的利用 Apache commons validator

When using manual validations very useful to utilize the Apache commons validator

if (GenericValidator.isBlankOrNull(value))
  addFieldError("FieldLabel", MessageFormat.format(getText("ErrorKey"),
    getText("FieldLabel"), new Object {}));

类似的代码可以用于 ActionErrors 和/或 ActionMessages 。 commons-validator包中提供了其他验证器，或者您可以使用不属于此问题的Struts2验证器。

The similar code could be done for ActionErrors and/or ActionMessages. Other validators are available in the commons-validator package, or you could use Struts2 validators that is out of this question.

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