发送Struts2响应时出现JSON编写器异常

Question

我遇到了很多例外，我发现这些例外对解决我的问题没有帮助，

这就是它们

Class org.apache.struts2.json.JSONWriter can not access a member of class org.hibernate.bytecode.internal.javassist.BytecodeProviderImpl$EntityInstrumentationMetadataImpl with modifiers "public"
java.lang.IllegalAccessException: Class org.apache.struts2.json.JSONWriter can not access a member of class org.hibernate.bytecode.internal.javassist.BytecodeProviderImpl$EntityInstrumentationMetadataImpl with modifiers "public"
org.apache.struts2.json.JSONException: java.lang.IllegalAccessException: Class org.apache.struts2.json.JSONWriter can not access a member of class org.hibernate.bytecode.internal.javassist.BytecodeProviderImpl$EntityInstrumentationMetadataImpl with modifiers "public"
org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: java.lang.IllegalAccessException: Class org.apache.struts2.json.JSONWriter can not access a member of class org.hibernate.bytecode.internal.javassist.BytecodeProviderImpl$EntityInstrumentationMetadataImpl with modifiers "public"
org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: java.lang.IllegalAccessException: Class org.apache.struts2.json.JSONWriter can not access a member of class org.hibernate.bytecode.internal.javassist.BytecodeProviderImpl$EntityInstrumentationMetadataImpl with modifiers "public"
org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: java.lang.IllegalAccessException: Class org.apache.struts2.json.JSONWriter can not access a member of class org.hibernate.bytecode.internal.javassist.BytecodeProviderImpl$EntityInstrumentationMetadataImpl with modifiers "public"
org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: java.lang.IllegalAccessException: Class org.apache.struts2.json.JSONWriter can not access a member of class org.hibernate.bytecode.internal.javassist.BytecodeProviderImpl$EntityInstrumentationMetadataImpl with modifiers "public"
org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: java.lang.IllegalAccessException: Class org.apache.struts2.json.JSONWriter can not access a member of class org.hibernate.bytecode.internal.javassist.BytecodeProviderImpl$EntityInstrumentationMetadataImpl with modifiers "public"

下面是我的action类，它返回JSON

public class GetTagsAction extends ActionSupport{       
    public String execute(){

        Gson gson = new Gson();
        String tags = gson.toJson(audioTaggingService.findTagsByName(q));
        System.out.println(tags);

        return Action.SUCCESS;
    }

    public String getQ() {
        return q;
    }

    public void setQ(String q) {
        this.q = q;
    }

    public AudioTaggingService getAudioTaggingService() {
        return audioTaggingService;
    }

    public void setAudioTaggingService(AudioTaggingService audioTaggingService) {
        this.audioTaggingService = audioTaggingService;
    }

    public String getTags() {
        return tags;
    }

    public void setTags(String tags) {
        this.tags = tags;
    }

    private String q;
    private AudioTaggingService audioTaggingService;
    private String tags;
}

这是包裹

<package name="default" namespace="/" extends="json-default">
    <!--  Get AJAX Related Actions -->
    <action name="tags" class="tags">
        <result type="json" />
    </action>
</package>

我使用的是Struts2-JSON-plugin

Answer 1

错误是由于插件试图转换整个对象图的事实，而且看起来插件试图通过audioTaggingService转换您的数据库层。您需要在struts XML中指定"root“参数。

<action name="tags" class="tags">
    <result type="json">
      <param name="root">tags</param>
    </result>
</action>

并在您的操作中提供getTags()方法。

然而，我不确定这是否会有帮助。当您尝试JSON化一个已经包含JSON数据的字符串时，我不确定会发生什么。

Answer 2

您需要在xml中编辑以下行

 <action name="tags" class="tags">

attribute class正在查找详细的类名，如com.your.package.YourAction

详细的here

Answer 3

有时，如果其中一个JSON数据为null，则会出现此错误，在转换时不会产生错误，但在处理数据时会产生错误。