Java Applet 无法解析 Json [英] Java Applet cannot parse Json
问题描述
我正在 Django 中开发一个 Web 服务器，并在一个页面中嵌入了一个 Java Applet.
I'm developing a web server in Django, and in a page, I embed a Java Applet.
我必须在实例化时将一个 JSon 数组传递给这个小程序.完全没有问题，我已经在 Eclipse 中对其进行了测试，没有任何错误或问题.
I have to pass to this applet a JSon array at the moment of instantiation. NO problems at all, I've tested it in Eclipse with no errors or problems.
当我把它放在网页上时，大问题就出来了.
The big problems came out when I put this on the web page.
首先我尝试使用 Jackson，这是页面上的代码:
First I tried with Jackson, here is the code on the page:
<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:
The Java code for parsing the Json:
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;
}
这是我尝试在网页中使用 Java 控制台时出现的错误:
And here it's the error that I get in the Java console when I try to use it in the web page:
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
所以我考虑了一些奇怪的实现问题，并尝试使用 google-gson
So I tought about some strange implementation problem, and I tried with google-gson
和之前一样，这里是网页代码:
As before here is the web page code:
<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>
Java 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;
}
我在 Eclipse 上运行小程序时没有遇到任何错误，但是当我在网页上进行测试时...我遇到另一个错误:
I don't get any error running the applet on Eclipse, but when I go testing on a web page... I get another error:
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)
这是我要解析的类 BaseFloor，它在静态函数的同一个包中:
Here is the class BaseFloor that I'm tryng to parse, it's in the same package of the static function:
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;
}
}
这是我传递给小程序的 JSON:
And here is the JSON that I'm passing to the applet:
[{"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:是我代码实现的问题，还是安全问题，因为我的小程序没有签名所以反射不能使用?
I'm curious: is it a problem of my implementation of the code, or is it a problem of security, because my applet isn't signed so the reflection cannot be used?
如果你需要什么，尽管问.
If you need something, ask freely.
提前致谢.
编辑
我已经尝试过你建议的@Nikita，错误发生了变化！
I've tried what you suggested @Nikita, and the error changed!
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)
推荐答案
尝试在页面中的 {{STATIC_URL}}jar/plugin.jar 后插入逗号.可能是 java 插件因此忽略了 jackson-annotations.jar 并且你得到 NoClassDefFoundError.
这是一个类似的问题:NoClassDefFoundError JsonAutoDetect while parsing JSON object 并缺少 jackson-annotations 导致了问题.
Try to insert comma after {{STATIC_URL}}jar/plugin.jar in your page. May be java plugin ignores jackson-annotations.jar because of this and you get NoClassDefFoundError.
Here is a similar question: NoClassDefFoundError JsonAutoDetect while parsing JSON object and missing jackson-annotations caused the problem.
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