我在使用Jackson（版本2.2.1）反序列化Exception和Throwable实例时遇到问题。请考虑以下代码段：
public static void main(String[] args) throws IOException
{
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(SerializationFeature.INDENT_OUTPUT, true);
objectMapper.setVisibility(PropertyAccessor.FIELD, Visibility.ANY);
objectMapper.enableDefaultTyping(DefaultTyping.NON_FINAL, As.PROPERTY);
try {
Integer.parseInt("String");
}
catch (NumberFormatException e) {
RuntimeException runtimeException = new RuntimeException(e);
String serializedException = objectMapper.writeValueAsString(runtimeException);
System.out.println(serializedException);
Throwable throwable = objectMapper.readValue(serializedException, Throwable.class);
throwable.printStackTrace();
}
}
System.out.println块中catch的输出为：
{
"@class" : "java.lang.RuntimeException",
"detailMessage" : "java.lang.NumberFormatException: For input string: \"String\"",
"cause" : {
"@class" : "java.lang.NumberFormatException",
"detailMessage" : "For input string: \"String\"",
"cause" : null,
"stackTrace" : [ {
"declaringClass" : "java.lang.NumberFormatException",
"methodName" : "forInputString",
"fileName" : "NumberFormatException.java",
"lineNumber" : 65
}, {
"declaringClass" : "java.lang.Integer",
"methodName" : "parseInt",
"fileName" : "Integer.java",
"lineNumber" : 492
}, {
"declaringClass" : "java.lang.Integer",
"methodName" : "parseInt",
"fileName" : "Integer.java",
"lineNumber" : 527
}, {
"declaringClass" : "test.jackson.JacksonTest",
"methodName" : "main",
"fileName" : "JacksonTest.java",
"lineNumber" : 26
} ],
"suppressedExceptions" : [ "java.util.ArrayList", [ ] ]
},
"stackTrace" : [ {
"declaringClass" : "test.jackson.JacksonTest",
"methodName" : "main",
"fileName" : "JacksonTest.java",
"lineNumber" : 29
} ],
"suppressedExceptions" : [ "java.util.ArrayList", [ ] ]
}
看起来很好。但是当我尝试使用objectMapper.readValue()反序列化时，我得到以下异常：
Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "declaringClass" (class java.lang.StackTraceElement), not marked as ignorable
at [Source: java.io.StringReader@3c5ebd39; line: 9, column: 27] (through reference chain: java.lang.StackTraceElement["declaringClass"])
at com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:79)
at com.fasterxml.jackson.databind.DeserializationContext.reportUnknownProperty(DeserializationContext.java:555)
at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:708)
at com.fasterxml.jackson.databind.deser.std.JdkDeserializers$StackTraceElementDeserializer.deserialize(JdkDeserializers.java:414)
at com.fasterxml.jackson.databind.deser.std.JdkDeserializers$StackTraceElementDeserializer.deserialize(JdkDeserializers.java:380)
at com.fasterxml.jackson.databind.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:151)
...
然后我尝试使用mix-in annotations忽略declaringClass中的java.lang.StackTraceElement，但现在反序列化的Exception在其堆栈跟踪中不包含声明类：
java.lang.RuntimeException: java.lang.NumberFormatException: For input string: "String"
at .main(JacksonTest.java:33)
Caused by: java.lang.NumberFormatException: For input string: "String"
at .forInputString(NumberFormatException.java:65)
at .parseInt(Integer.java:492)
at .parseInt(Integer.java:527)
at .main(JacksonTest.java:30)
我错过了什么吗？非常感谢任何帮助。
答案 0 :(得分：6)
这个here似乎有杰克逊JIRA条目。杰克逊似乎无法处理declaringClass中的java.lang.StackTraceElement，因为与此字段对应的getter称为getClassName()。
我按照上面提到的JIRA条目中的建议，使用StackTraceElement周围的自定义包装来修复此问题。自定义包装器（CustomStackTraceElement）将包含字段declaringClass，methodName，fileName和lineNumber以及相应的getter和setter。我将catch块（在问题中提到）修改为如下：
catch (NumberFormatException e) {
RuntimeException runtimeException = new RuntimeException(e);
e.printStackTrace();
String serializedException = objectMapper.writeValueAsString(runtimeException);
System.out.println(serializedException);
String serializedStackTrace = objectMapper.writeValueAsString(transformStackTrace(runtimeException));
String serializedStackTraceForCause = objectMapper.writeValueAsString(transformStackTrace(runtimeException.getCause()));
Throwable throwable = objectMapper.readValue(serializedException, Throwable.class);
List<CustomStackTraceElement> customStackTraceElementList = objectMapper.readValue(serializedStackTrace, List.class);
List<CustomStackTraceElement> customStackTraceElementListForCause = objectMapper.readValue(serializedStackTraceForCause, List.class);
throwable.setStackTrace(reverseTransformStackTrace(customStackTraceElementList));
throwable.getCause().setStackTrace(reverseTransformStackTrace(customStackTraceElementListForCause));
throwable.printStackTrace();
}
序列化期间，StackTraceElement[]将通过以下方法转换为List<CustomStackTraceElement>：
private static List<CustomStackTraceElement> transformStackTrace(Throwable throwable)
{
List<CustomStackTraceElement> list = new ArrayList<>();
for (StackTraceElement stackTraceElement : throwable.getStackTrace()) {
CustomStackTraceElement customStackTraceElement =
new CustomStackTraceElement(stackTraceElement.getClassName(),
stackTraceElement.getMethodName(),
stackTraceElement.getFileName(),
stackTraceElement.getLineNumber());
list.add(customStackTraceElement);
}
return list;
}
...并且在反序列化期间将进行反向转换：
private static StackTraceElement[] reverseTransformStackTrace(List<CustomStackTraceElement> customStackTraceElementList)
{
StackTraceElement[] stackTraceElementArray = new StackTraceElement[customStackTraceElementList.size()];
for (int i = 0; i < customStackTraceElementList.size(); i++) {
CustomStackTraceElement customStackTraceElement = customStackTraceElementList.get(i);
StackTraceElement stackTraceElement =
new StackTraceElement(customStackTraceElement.getDeclaringClass(),
customStackTraceElement.getMethodName(),
customStackTraceElement.getFileName(),
customStackTraceElement.getLineNumber());
stackTraceElementArray[i] = stackTraceElement;
}
return stackTraceElementArray;
}
现在，在反序列化之后，Throwable对象中包含了预期的堆栈跟踪。
答案 1 :(得分：2)
添加：
objectMapper.configure( DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
以同样的方式完成反序列化的异常，就像第一次一样：
System.out.println( objectMapper.writeValueAsString( throwable ) );
我使用了以下代码：
public static void main( String[] args ) throws IOException
{
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure( SerializationFeature.INDENT_OUTPUT, true );
objectMapper.configure( DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
objectMapper.setVisibility( PropertyAccessor.FIELD, JsonAutoDetect.Visibility.ANY );
objectMapper.enableDefaultTyping( ObjectMapper.DefaultTyping.NON_FINAL, JsonTypeInfo.As.PROPERTY );
try
{
Integer.parseInt( "String" );
}
catch( NumberFormatException e )
{
Throwable throwable = objectMapper.readValue( objectMapper.writeValueAsString( e ), Throwable.class );
System.out.println( objectMapper.writeValueAsString( throwable ) );
}
}
添加了这个罐子：jackson-annotations-2.2.0.jar，jackson-core-2.2.0.jar和jackson-databind-2.2.0.jar。
执行后，将打印以下内容：
{
"@class" : "java.lang.NumberFormatException",
"detailMessage" : "For input string: \"String\"",
"cause" : null,
"stackTrace" : [ {
"declaringClass" : "java.lang.NumberFormatException",
"methodName" : "forInputString",
"fileName" : "NumberFormatException.java",
"lineNumber" : 48,
"className" : "java.lang.NumberFormatException",
"nativeMethod" : false
}, {
"declaringClass" : "java.lang.Integer",
"methodName" : "parseInt",
"fileName" : "Integer.java",
"lineNumber" : 449,
"className" : "java.lang.Integer",
"nativeMethod" : false
}, {
"declaringClass" : "java.lang.Integer",
"methodName" : "parseInt",
"fileName" : "Integer.java",
"lineNumber" : 499,
"className" : "java.lang.Integer",
"nativeMethod" : false
}, {
"declaringClass" : "com.sample.bla.Main",
"methodName" : "main",
"fileName" : "Main.java",
"lineNumber" : 24,
"className" : "com.sample.bla.Main",
"nativeMethod" : false
}, {
"declaringClass" : "sun.reflect.NativeMethodAccessorImpl",
"methodName" : "invoke0",
"fileName" : "NativeMethodAccessorImpl.java",
"lineNumber" : -2,
"className" : "sun.reflect.NativeMethodAccessorImpl",
"nativeMethod" : true
}, {
"declaringClass" : "sun.reflect.NativeMethodAccessorImpl",
"methodName" : "invoke",
"fileName" : "NativeMethodAccessorImpl.java",
"lineNumber" : 39,
"className" : "sun.reflect.NativeMethodAccessorImpl",
"nativeMethod" : false
}, {
"declaringClass" : "sun.reflect.DelegatingMethodAccessorImpl",
"methodName" : "invoke",
"fileName" : "DelegatingMethodAccessorImpl.java",
"lineNumber" : 25,
"className" : "sun.reflect.DelegatingMethodAccessorImpl",
"nativeMethod" : false
}, {
"declaringClass" : "java.lang.reflect.Method",
"methodName" : "invoke",
"fileName" : "Method.java",
"lineNumber" : 597,
"className" : "java.lang.reflect.Method",
"nativeMethod" : false
}, {
"declaringClass" : "com.intellij.rt.execution.application.AppMain",
"methodName" : "main",
"fileName" : "AppMain.java",
"lineNumber" : 120,
"className" : "com.intellij.rt.execution.application.AppMain",
"nativeMethod" : false
} ],
"message" : "For input string: \"String\"",
"localizedMessage" : "For input string: \"String\""
}
答案 2 :(得分：1)
似乎您在2.2.1版本中获得的输出与我在2.2.0版本中获得的输出不同（根据该网站是最新的2.x版本）。除了Maven Repository上最新的2.x版本是2.2.2。所以我会尝试将其降级到2.2.0或将其升级到2.2.2。如果任何更改为您带来预期结果，我会更进一步使用该版本并在Jackson的JIRA中打开一个BUG。
当然不要忘记
objectMapper.configure( DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
来自迈克尔的答案。
答案 3 :(得分：1)
我遇到了类似的问题。我现在正在使用此代码，它允许我使用适当的类型序列化和反序列化异常（即RuntimeException将再次成为RuntimeException :)）：
public static ObjectMapper createObjectMapper() {
ObjectMapper mapper = new ObjectMapper(null, null, new DefaultDeserializationContext.Impl(
new BeanDeserializerFactory(new DeserializerFactoryConfig()) {
private static final long serialVersionUID = 1L;
@Override
public JsonDeserializer<Object> buildThrowableDeserializer(
DeserializationContext ctxt, JavaType type, BeanDescription beanDesc)
throws JsonMappingException {
return super.buildBeanDeserializer(ctxt, type, beanDesc);
}
}));
mapper.setVisibility(PropertyAccessor.ALL, Visibility.NONE);
mapper.setVisibility(PropertyAccessor.FIELD, Visibility.ANY);
mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
mapper.addMixIn(Throwable.class, ThrowableMixin.class);
mapper.addMixIn(StackTraceElement.class, StackTraceElementMixin.class);
return mapper;
}
@JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, include = JsonTypeInfo.As.PROPERTY, property = "@class")
@JsonAutoDetect(fieldVisibility = Visibility.ANY)
@JsonIgnoreProperties({ "message", "localizedMessage", "suppressed" })
abstract class ThrowableMixin {
@JsonIdentityInfo(generator = ObjectIdGenerators.IntSequenceGenerator.class, property = "$id")
private Throwable cause;
}
abstract class StackTraceElementMixin {
@JsonProperty("className")
private String declaringClass;
}
我正在操纵BeanDeserializerFactory使buildThrowableDeserializer不对待Throwable任何特殊情况，但就像其他Object一样。然后使用Mixins根据我的喜好定义Throwable和StackTraceElement的“特殊”处理。
答案 4 :(得分：0)
是否有必要使用json序列化？看起来像throwables有一些错误。为什么不使用system api：
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream( );
ObjectOutputStream objectOutputStream = new ObjectOutputStream( byteArrayOutputStream );
objectOutputStream.writeObject( e );
ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream( byteArrayOutputStream.toByteArray() );
ObjectInputStream objectInputStream = new ObjectInputStream( byteArrayInputStream );
Throwable t = (Throwable) objectInputStream.readObject();
答案 5 :(得分：0)
尝试使用多态，以便jackson反序列化器知道要创建什么类型的Throwable：
/**
* Jackson module to serialize / deserialize Throwable
*/
public class ThrowableModule extends SimpleModule {
public ThrowableModule() {
super("Throwable", new Version(1, 0, 0, null, null, null));
}
@Override
public void setupModule(SetupContext context) {
context.setMixInAnnotations(Throwable.class, ThrowableAnnotations.class);
}
/**
* Add annotation to Throwable so that the class name is serialized with the instance data.
*/
@JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, include = JsonTypeInfo.As.PROPERTY, property = "class")
static abstract class ThrowableAnnotations {
}
}