Java小程序无法解析Json

Question

我正在Django开发一个web服务器，并在一个页面中嵌入了一个Java Applet。

在实例化时，我必须向这个applet传递一个JSon数组。没有任何问题，我在Eclipse中测试过它，没有任何错误或问题。

当我把这个放到网页上时，大问题就出现了。

首先我尝试了Jackson，这是页面上的代码：

  <applet name="mapGenerator"
            id="mapGenerator"  
            code="main.MapGenerator.class"
            archive="{{STATIC_URL}}jar/MapGenerator.jar, 
                            {{STATIC_URL}}jar/plugin.jar
                            {{STATIC_URL}}jar/jackson-annotations-2.1.1.jar,
                            {{STATIC_URL}}jar/jackson-core-2.1.1.jar,
                            {{STATIC_URL}}jar/jackson-databind-2.1.1.jar"
                     >
                    <param name=id value="{{building.id}}">
                    <param name=piani value='{{floors}}'>  
            MAYSCRIPT
    </applet>

解析Json的Java代码：

  public static  Floor[] parse(String input, URL codebase) {

        ObjectMapper mapper = new ObjectMapper(); // can reuse, share globally
    BaseFloor[] bfloors=null;

        try {
              bfloors = mapper.readValue(input, BaseFloor[].class);
    } catch (JsonParseException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (JsonMappingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
          for (int i=0; i < bfloors.length; i++) {

        Floor f = new Floor(bfloors[i]);
        f.setCodeBase(codebase);
        floors[i] = f;
    }
    return floors;
}

这是我在网页中尝试使用Java控制台时在Java控制台中得到的错误：

  Exception in thread "thread applet-main.MapGenerator.class-1" java.lang.NoClassDefFoundError: com/fasterxml/jackson/annotation/JsonAutoDetect
at com.fasterxml.jackson.databind.introspect.VisibilityChecker$Std.<clinit>(VisibilityChecker.java:172)
at com.fasterxml.jackson.databind.ObjectMapper.<clinit>(ObjectMapper.java:195)
at objects.Floor.parse(Floor.java:37)
at main.MapGenerator.loadParameters(MapGenerator.java:67)
at main.MapGenerator.start(MapGenerator.java:31)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Plugin2Manager.java:1698)
at java.lang.Thread.run(Thread.java:662)
  Caused by: java.lang.ClassNotFoundException: com.fasterxml.jackson.annotation.JsonAutoDetect
at sun.plugin2.applet.Applet2ClassLoader.findClass(Applet2ClassLoader.java:252)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass0(Plugin2ClassLoader.java:250)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Plugin2ClassLoader.java:180)
at sun.plugin2.applet.Plugin2ClassLoader.loadClass(Plugin2ClassLoader.java:161)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
... 7 more

所以我思考了一些奇怪的实现问题，我尝试使用google-gson。

和以前一样，这里是网页代码：

   <applet name="mapGenerator"
            id="mapGenerator"  
            code="main.MapGenerator.class"
            archive="{{STATIC_URL}}jar/MapGenerator.jar, 
                            {{STATIC_URL}}jar/gson-2.2.2.jar,
                            {{STATIC_URL}}jar/plugin.jar
                     >
                    <param name=id value="{{building.id}}">
                    <param name=piani value='{{floors}}'>  
            MAYSCRIPT
    </applet>

和爪哇代码：

  public static  Floor[] parse(String input, URL codebase) {

    Gson gson = new Gson();

    BaseFloor[] bfloors = gson.fromJson(input, BaseFloor[].class);

    Floor[] floors = new Floor[bfloors.length];

    for (int i=0; i < bfloors.length; i++) {

        Floor f = new Floor(bfloors[i]);
        f.setCodeBase(codebase);
        floors[i] = f;
    }
    return floors;
}

在Eclipse上运行applet时，我没有收到任何错误，但当我在网页上测试时，我收到另一个错误：

  java.security.AccessControlException: access denied (java.lang.reflect.ReflectPermission suppressAccessChecks)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:374)
at java.security.AccessController.checkPermission(AccessController.java:546)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at java.lang.reflect.AccessibleObject.setAccessible(AccessibleObject.java:107)
at com.google.gson.internal.ConstructorConstructor.newDefaultConstructor(ConstructorConstructor.java:84)
at com.google.gson.internal.ConstructorConstructor.get(ConstructorConstructor.java:66)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory.create(ReflectiveTypeAdapterFactory.java:71)
at com.google.gson.Gson.getAdapter(Gson.java:353)
at com.google.gson.internal.bind.ArrayTypeAdapter$1.create(ArrayTypeAdapter.java:48)
at com.google.gson.Gson.getAdapter(Gson.java:353)
at com.google.gson.Gson.fromJson(Gson.java:794)
at com.google.gson.Gson.fromJson(Gson.java:761)
at com.google.gson.Gson.fromJson(Gson.java:710)
at com.google.gson.Gson.fromJson(Gson.java:682)
at objects.Floor.parse(Floor.java:33)
at main.MapGenerator.loadParameters(MapGenerator.java:67)
at main.MapGenerator.start(MapGenerator.java:31)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Plugin2Manager.java:1698)
at java.lang.Thread.run(Thread.java:662)
  Eccezione: java.security.AccessControlException: access denied (java.lang.reflect.ReflectPermission suppressAccessChecks)

下面是我尝试解析的类 BaseFloor，它位于静态函数的同一包中：

  package objects;


  public class BaseFloor {

      public int numero_di_piano;
      public String link;
      public String bearing;

      public float getBearing() {
    return Float.parseFloat(bearing);
      }

      public int getFloor() {
    return numero_di_piano;
      }

      public String getLink() {
    return link;
      }

      public String toString() {
    return numero_di_piano + " " + bearing + " " + link;
      }
  }

这是我传递给applet的JSON:

  [{"bearing": "354.00", "link": "/media/floors/Foto_del_63333991-02-2455618_alle_17_35_6.jpg", "numero_di_piano": 0}, {"bearing": "354.00", "link": "/media/floors/IMG_20111009_171138_7.jpg", "numero_di_piano": 1}]

我很好奇：这是我代码实现的问题，还是安全问题，因为我的applet没有签名，所以反射无法使用？

如果你需要什么，自由地问。

提前感谢。

编辑

我已经尝试了您@Nikita的建议，并且错误已更改！

  java.security.AccessControlException: access denied (java.lang.RuntimePermission accessDeclaredMembers)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:374)
at java.security.AccessController.checkPermission(AccessController.java:546)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
at java.lang.SecurityManager.checkMemberAccess(SecurityManager.java:1662)
at java.lang.Class.checkMemberAccess(Class.java:2157)
at java.lang.Class.getDeclaredMethods(Class.java:1790)
at com.fasterxml.jackson.databind.introspect.AnnotatedClass._addMemberMethods(AnnotatedClass.java:593)
at com.fasterxml.jackson.databind.introspect.AnnotatedClass.resolveMemberMethods(AnnotatedClass.java:421)
at com.fasterxml.jackson.databind.introspect.AnnotatedClass.memberMethods(AnnotatedClass.java:243)
at com.fasterxml.jackson.databind.introspect.POJOPropertiesCollector._addMethods(POJOPropertiesCollector.java:442)
at com.fasterxml.jackson.databind.introspect.POJOPropertiesCollector.collect(POJOPropertiesCollector.java:232)
at com.fasterxml.jackson.databind.introspect.BasicClassIntrospector.collectProperties(BasicClassIntrospector.java:142)
at com.fasterxml.jackson.databind.introspect.BasicClassIntrospector.forDeserialization(BasicClassIntrospector.java:81)
at com.fasterxml.jackson.databind.introspect.BasicClassIntrospector.forDeserialization(BasicClassIntrospector.java:11)
at com.fasterxml.jackson.databind.DeserializationConfig.introspect(DeserializationConfig.java:507)
at com.fasterxml.jackson.databind.deser.DeserializerCache._createDeserializer(DeserializerCache.java:326)
at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCache2(DeserializerCache.java:264)
at com.fasterxml.jackson.databind.deser.DeserializerCache._createAndCacheValueDeserializer(DeserializerCache.java:244)
at com.fasterxml.jackson.databind.deser.DeserializerCache.findValueDeserializer(DeserializerCache.java:143)
at com.fasterxml.jackson.databind.DeserializationContext.findRootValueDeserializer(DeserializationContext.java:342)
at com.fasterxml.jackson.databind.ObjectMapper._findRootDeserializer(ObjectMapper.java:2898)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2792)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:1942)
at objects.Floor.parse(Floor.java:40)
at main.MapGenerator.loadParameters(MapGenerator.java:67)
at main.MapGenerator.start(MapGenerator.java:31)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Plugin2Manager.java:1698)
at java.lang.Thread.run(Thread.java:662)
  Eccezione: java.security.AccessControlException: access denied (java.lang.RuntimePermission accessDeclaredMembers)

Answer 1

尝试在页面中的 {{STATIC_URL}} jar/插件.jar后插入逗号。可能是Java插件忽略了杰克逊注释.jar因此而得到没有类的efFoundEror。
下面是一个类似的问题：在解析 JSON 对象和缺少杰克逊注释时，没有类定义错误错误 Json 自动检测导致了问题。