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从Struts2动作返回JSON消息

jqueryajaxjsonstruts2jackson
3
我在我的Web应用程序中使用了jQuery和Struts2。现在我需要将Google地图嵌入到我的网页中并添加一些标记。我使用jQuery.getJSON()命令向Struts2 action发送请求。
在struts.xml中：
<package name="ajax" namespace="/ajax" extends="json-default">
    <action name="LatLngList" class="com.test.ajax.Action" method="find">
        <result type="json"></result>
    </action>
</package>

在网页中。
<script type="text/javascript">
    function readLatLng() { 
        var latitude = new Array();
        var longitude = new Array();
        $.getJSON("ajax/LatLngList.action?id=9", function(data){
            $.each(data, function(i,latlng){
            latitude.push(latlng.latitude);
            longitude.push(latlng.longitude);       
            });
        });
    }
</script>

在这个操作中，我从数据库读取数据并创建了一个对象列表，然后使用Jackson JSON处理器的ObjectMapper将该列表转换为JSON字符串。最后，我将JSON字符串作为返回值返回。
public String find() throws JsonGenerationException, JsonMappingException, IOException {

    List latlngList = new ArrayList();
    /*
    latlngList.add(...);
    */

    ObjectMapper mapper = new ObjectMapper();
    String str = mapper.writeValueAsString(latlngList);
    System.out.println(str);
    return str;
}

当我运行Web应用程序时，JSON字符串显示在控制台中：
[
{"latitude":37.7935697,"longitude":121.181969},

{"latitude":37.7852119,"longitude":121.1759833},

{"latitude":37.7858117,"longitude":121.1250904},

{"latitude":37.794129,"longitude":121.1229535},

{"latitude":37.7974078,"longitude":121.0874301},

{"latitude":37.8280231,"longitude":121.049312}
]

然而，它给出了错误信息。
No result defined for action com.test.ajax.Action and result [{"latitude":37.7935697,"longitude":121.181969},{"latitude":37.7852119,"longitude":121.1759833},{"latitude":37.7858117,"longitude":121.1250904},{"latitude":37.794129,"longitude":121.1229535},{"latitude":37.7974078,"longitude":121.0874301},{"latitude":37.8280231,"longitude":121.049312}]
    at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:375)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:277)
    at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:263)
    at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:133)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:207)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:94)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:243)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:270)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)
    at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:190)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:248)
    at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)
    at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:498)
    at org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
    at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:291)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Thread.java:680)

我已经搜索了很长时间，但仍然找不到解决方案。等待您的帮助。非常感谢。
2个回答
6

我很久没有使用Struts2了，但从记忆中来看，你不是直接从action返回响应，而是返回一个简单的字符串名称，该名称确定要使用配置中的哪个结果，然后控制器类上的属性就可用于您的视图。当返回json结果时，这些属性会被序列化为JSON并返回。

因此，您需要像这样的内容：

private List latlngList;
public List getLatLngList() {
    return latlngList;
}

public String find() throws JsonGenerationException, JsonMappingException, IOException {
    latlngList = new ArrayList()
    /*
    latlngList.add(...);
    */

    return "success";
}

然后在您的JavaScript中抓取结果JSON的LatLngList属性（注意从data更改为data.latLngList）：

<script type="text/javascript">
    function readLatLng() { 
        var latitude = new Array();
        var longitude = new Array();
        $.getJSON("ajax/LatLngList.action?id=9", function(data){
            $.each(data.latLngList, function(i,latlng){
                latitude.push(latlng.latitude);
                longitude.push(latlng.longitude);       
            });
        });
    }
</script>
1
非常感谢。它成功返回了JSON文件。我误解了struts2的返回过程。 - Fan Wu
2
因为你正在混合使用 JSON 插件和直接渲染结果，这意味着两者都无法正常工作。操作返回结果的名称，而不是原始数据。（或者更确切地说，它们可以返回原始数据，但必须以不同的方式处理。）
请查看 JSON 插件的文档。
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