Class ExtensionRegistry
- java.lang.Object
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- akka.protobuf.ExtensionRegistryLite
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- akka.protobuf.ExtensionRegistry
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public final class ExtensionRegistry extends ExtensionRegistryLite
A table of known extensions, searchable by name or field number. When parsing a protocol message that might have extensions, you must provide anExtensionRegistry
in which you have registered any extensions that you want to be able to parse. Otherwise, those extensions will just be treated like unknown fields.For example, if you had the
.proto
file:option java_class = "MyProto"; message Foo { extensions 1000 to max; } extend Foo { optional int32 bar; }
Then you might write code like:ExtensionRegistry registry = ExtensionRegistry.newInstance(); registry.add(MyProto.bar); MyProto.Foo message = MyProto.Foo.parseFrom(input, registry);
Background:
You might wonder why this is necessary. Two alternatives might come to mind. First, you might imagine a system where generated extensions are automatically registered when their containing classes are loaded. This is a popular technique, but is bad design; among other things, it creates a situation where behavior can change depending on what classes happen to be loaded. It also introduces a security vulnerability, because an unprivileged class could cause its code to be called unexpectedly from a privileged class by registering itself as an extension of the right type.
Another option you might consider is lazy parsing: do not parse an extension until it is first requested, at which point the caller must provide a type to use. This introduces a different set of problems. First, it would require a mutex lock any time an extension was accessed, which would be slow. Second, corrupt data would not be detected until first access, at which point it would be much harder to deal with it. Third, it could violate the expectation that message objects are immutable, since the type provided could be any arbitrary message class. An unprivileged user could take advantage of this to inject a mutable object into a message belonging to privileged code and create mischief.
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
ExtensionRegistry.ExtensionInfo
A (Descriptor, Message) pair, returned by lookup methods.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description void
add(Descriptors.FieldDescriptor type)
Add a non-message-type extension to the registry by descriptor.void
add(Descriptors.FieldDescriptor type, Message defaultInstance)
Add a message-type extension to the registry by descriptor.void
add(GeneratedMessage.GeneratedExtension<?,?> extension)
Add an extension from a generated file to the registry.ExtensionRegistry.ExtensionInfo
findExtensionByName(java.lang.String fullName)
Find an extension by fully-qualified field name, in the proto namespace.ExtensionRegistry.ExtensionInfo
findExtensionByNumber(Descriptors.Descriptor containingType, int fieldNumber)
Find an extension by containing type and field number.static ExtensionRegistry
getEmptyRegistry()
Get the unmodifiable singleton empty instance.ExtensionRegistry
getUnmodifiable()
Returns an unmodifiable view of the registry.static ExtensionRegistry
newInstance()
Construct a new, empty instance.-
Methods inherited from class akka.protobuf.ExtensionRegistryLite
add, findLiteExtensionByNumber, isEagerlyParseMessageSets, setEagerlyParseMessageSets
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Method Detail
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newInstance
public static ExtensionRegistry newInstance()
Construct a new, empty instance.
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getEmptyRegistry
public static ExtensionRegistry getEmptyRegistry()
Get the unmodifiable singleton empty instance.
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getUnmodifiable
public ExtensionRegistry getUnmodifiable()
Returns an unmodifiable view of the registry.- Overrides:
getUnmodifiable
in classExtensionRegistryLite
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findExtensionByName
public ExtensionRegistry.ExtensionInfo findExtensionByName(java.lang.String fullName)
Find an extension by fully-qualified field name, in the proto namespace. I.e.result.descriptor.fullName()
will matchfullName
if a match is found.- Returns:
- Information about the extension if found, or
null
otherwise.
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findExtensionByNumber
public ExtensionRegistry.ExtensionInfo findExtensionByNumber(Descriptors.Descriptor containingType, int fieldNumber)
Find an extension by containing type and field number.- Returns:
- Information about the extension if found, or
null
otherwise.
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add
public void add(GeneratedMessage.GeneratedExtension<?,?> extension)
Add an extension from a generated file to the registry.
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add
public void add(Descriptors.FieldDescriptor type)
Add a non-message-type extension to the registry by descriptor.
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add
public void add(Descriptors.FieldDescriptor type, Message defaultInstance)
Add a message-type extension to the registry by descriptor.
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