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public interface ExclusionStrategy
A strategy (or policy) definition that is used to decide whether or not a field or top-level class should be serialized or deserialized as part of the JSON output/input. For serialization, if theshouldSkipClass(Class)
method returns true then that class or field type will not be part of the JSON output. For deserialization, ifshouldSkipClass(Class)
returns true, then it will not be set as part of the Java object structure.The following are a few examples that shows how you can use this exclusion mechanism.
Exclude fields and objects based on a particular class type:
private static class SpecificClassExclusionStrategy implements ExclusionStrategy { private final Class<?> excludedThisClass; public SpecificClassExclusionStrategy(Class<?> excludedThisClass) { this.excludedThisClass = excludedThisClass; } public boolean shouldSkipClass(Class<?> clazz) { return excludedThisClass.equals(clazz); } public boolean shouldSkipField(FieldAttributes f) { return excludedThisClass.equals(f.getDeclaredClass()); } }
Excludes fields and objects based on a particular annotation:
public @interface FooAnnotation { // some implementation here } // Excludes any field (or class) that is tagged with an "@FooAnnotation" private static class FooAnnotationExclusionStrategy implements ExclusionStrategy { public boolean shouldSkipClass(Class<?> clazz) { return clazz.getAnnotation(FooAnnotation.class) != null; } public boolean shouldSkipField(FieldAttributes f) { return f.getAnnotation(FooAnnotation.class) != null; } }
Now if you want to configure
Gson
to use a user defined exclusion strategy, then theGsonBuilder
is required. The following is an example of how you can use theGsonBuilder
to configure Gson to use one of the above sample:ExclusionStrategy excludeStrings = new UserDefinedExclusionStrategy(String.class); Gson gson = new GsonBuilder() .setExclusionStrategies(excludeStrings) .create();
For certain model classes, you may only want to serialize a field, but exclude it for deserialization. To do that, you can write an
ExclusionStrategy
as per normal; however, you would register it with theGsonBuilder.addDeserializationExclusionStrategy(ExclusionStrategy)
method. For example:ExclusionStrategy excludeStrings = new UserDefinedExclusionStrategy(String.class); Gson gson = new GsonBuilder() .addDeserializationExclusionStrategy(excludeStrings) .create();
- Since:
- 1.4
- Author:
- Inderjeet Singh, Joel Leitch
- See Also:
GsonBuilder.setExclusionStrategies(ExclusionStrategy...)
,GsonBuilder.addDeserializationExclusionStrategy(ExclusionStrategy)
,GsonBuilder.addSerializationExclusionStrategy(ExclusionStrategy)
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description boolean
shouldSkipClass(Class<?> clazz)
boolean
shouldSkipField(FieldAttributes f)
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Method Detail
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shouldSkipField
boolean shouldSkipField(FieldAttributes f)
- Parameters:
f
- the field object that is under test- Returns:
- true if the field should be ignored; otherwise false
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shouldSkipClass
boolean shouldSkipClass(Class<?> clazz)
- Parameters:
clazz
- the class object that is under test- Returns:
- true if the class should be ignored; otherwise false
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