Details
Improvement
Closed
Major
Description
In Jenkin's custom ReflectionConverter implementation, we'd like to read into transient fields (for backward compatibility when evolving classes) without writing transient fields.
To do this, we check if the field is defined in a given class. To do this efficiently, we created {{ReflectionProvider.getFieldOrNull(Class definedIn, String fieldName)}.
This method works like getField except that instead of throwing an exception (which is costly performance-wise), it returns null.
Note that this method defers from the fieldDefinedInClass method in that it still finds fields that are marked transient.
Activity
You can already do this with:
xstream.registerConverter(new ReflectionConverter( xstream.getMapper(), xstream.getReflectionProvider(), XStream.PRIORITY_VERY_LOW) { protected boolean shouldUnmarshalTransientFields() { return true; } }); xstream.registerConverter(new SerializableConverter( xstream.getMapper(), xstream.getReflectionProvider(), XStream.PRIORITY_LOW) { protected boolean shouldUnmarshalTransientFields() { return true; } });
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Jörg Schaible
added a comment - - edited You can already do this with:
xstream.registerConverter( new ReflectionConverter(
xstream.getMapper(), xstream.getReflectionProvider(), XStream.PRIORITY_VERY_LOW) {
protected boolean shouldUnmarshalTransientFields() {
return true ;
}
});
xstream.registerConverter( new SerializableConverter(
xstream.getMapper(), xstream.getReflectionProvider(), XStream.PRIORITY_LOW) {
protected boolean shouldUnmarshalTransientFields() {
return true ;
}
});
Jörg Schaible
added a comment - - edited You can already do this with:
xstream.registerConverter( new ReflectionConverter(
xstream.getMapper(), xstream.getReflectionProvider(), XStream.PRIORITY_VERY_LOW) {
protected boolean shouldUnmarshalTransientFields() {
return true ;
}
});
xstream.registerConverter( new SerializableConverter(
xstream.getMapper(), xstream.getReflectionProvider(), XStream.PRIORITY_LOW) {
protected boolean shouldUnmarshalTransientFields() {
return true ;
}
});
Our custom ReflectionConverter implementation doesn't actually derive from ReflectionConverter. It does something very similar, but it implements Converter directly as it does many other things beside this.
What's relevant here is that my custom reflection converter tolerates elements that are unknown. In contrast, XStream chokes if it encounters an element that makes no sense there. This is where I need to be able to do getField and catch an exception. So I still request that you kindly consider applying this patch.
Exception in thread "main" com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter$UnknownFieldException: No such field jenkins.FooTest.z ---- Debugging information ---- field : z class : jenkins.FooTest required-type : jenkins.FooTest converter-type : com.thoughtworks.xstream.converters.reflection.ReflectionConverter path : /jenkins.FooTest/z line number : 1 version : null ------------------------------- at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.determineType(AbstractReflectionConverter.java:453) at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doUnmarshal(AbstractReflectionConverter.java:294) at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:234) at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72) at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65) at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66) at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50) at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134) at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32) at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1061) at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1045) at com.thoughtworks.xstream.XStream.fromXML(XStream.java:916) at com.thoughtworks.xstream.XStream.fromXML(XStream.java:907) at jenkins.FooTest.main(FooTest.java:13) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)
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Kohsuke Kawaguchi
added a comment - Our custom ReflectionConverter implementation doesn't actually derive from ReflectionConverter . It does something very similar, but it implements Converter directly as it does many other things beside this.
What's relevant here is that my custom reflection converter tolerates elements that are unknown. In contrast, XStream chokes if it encounters an element that makes no sense there. This is where I need to be able to do getField and catch an exception. So I still request that you kindly consider applying this patch.
Exception in thread "main" com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter$UnknownFieldException: No such field jenkins.FooTest.z
---- Debugging information ----
field : z
class : jenkins.FooTest
required-type : jenkins.FooTest
converter-type : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
path : /jenkins.FooTest/z
line number : 1
version : null
-------------------------------
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.determineType(AbstractReflectionConverter.java:453)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doUnmarshal(AbstractReflectionConverter.java:294)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:234)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1061)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1045)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:916)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:907)
at jenkins.FooTest.main(FooTest.java:13)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)
Kohsuke Kawaguchi
added a comment - Our custom ReflectionConverter implementation doesn't actually derive from ReflectionConverter . It does something very similar, but it implements Converter directly as it does many other things beside this.
What's relevant here is that my custom reflection converter tolerates elements that are unknown. In contrast, XStream chokes if it encounters an element that makes no sense there. This is where I need to be able to do getField and catch an exception. So I still request that you kindly consider applying this patch.
Exception in thread "main" com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter$UnknownFieldException: No such field jenkins.FooTest.z
---- Debugging information ----
field : z
class : jenkins.FooTest
required-type : jenkins.FooTest
converter-type : com.thoughtworks.xstream.converters.reflection.ReflectionConverter
path : /jenkins.FooTest/z
line number : 1
version : null
-------------------------------
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.determineType(AbstractReflectionConverter.java:453)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.doUnmarshal(AbstractReflectionConverter.java:294)
at com.thoughtworks.xstream.converters.reflection.AbstractReflectionConverter.unmarshal(AbstractReflectionConverter.java:234)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1061)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1045)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:916)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:907)
at jenkins.FooTest.main(FooTest.java:13)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)
Applied. However, I am inclined to modify the implementation before the release to return only supported fields, i.e. the ReflectionProvider would not return static fields. Would that affect you?
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Jörg Schaible
added a comment - Applied. However, I am inclined to modify the implementation before the release to return only supported fields, i.e. the ReflectionProvider would not return static fields. Would that affect you?
Jörg Schaible
added a comment - Applied. However, I am inclined to modify the implementation before the release to return only supported fields, i.e. the ReflectionProvider would not return static fields. Would that affect you? 
Patch attached. This method simply exposes what's already defined in FieldDictionary.fieldOrNull.