com.google.gwt.core.ext
Class Linker

java.lang.Object
  com.google.gwt.core.ext.Linker

Direct Known Subclasses:

AbstractLinker, SoycReportLinker

public abstract class Linker
extends java.lang.Object

Defines a linker for the GWT compiler. Each Linker must be annotated with a LinkerOrder annotation to determine the relative ordering of the Linkers. Exact order of Linker execution will be determined by the order of add-linker tags in the module configuration. Each Linker should also be annotated with Shardable; non-shardable linkers are deprecated and will eventually not be supported.

A new instance of a linker is created each time a module is compiled or during hosted mode when a module first loads (or is refreshed). During a compile, link(TreeLogger, LinkerContext, ArtifactSet) is called exactly once on each non-shardable linker, and the artifact set will contain any and all generated artifacts. For shardable linkers, link(TreeLogger, LinkerContext, ArtifactSet, boolean) is called once for each compiled permutation and once after all compiles are finished. The precise artifacts supplied differ with each call and are described in the method's documentation.

When hosted mode starts for a module, it calls link(TreeLogger, LinkerContext, ArtifactSet) for non-shardable linkers and link(TreeLogger, LinkerContext, ArtifactSet, boolean) for shardable ones, passing false as the onePermutation argument. If any artifacts are subsequently generated during the course of running hosted mode, relink(TreeLogger, LinkerContext, ArtifactSet) will be called with the new artifacts.

Linker

public Linker()

getDescription

public abstract java.lang.String getDescription()

Returns a human-readable String describing the Linker.

isShardable

public final boolean isShardable()

Check whether this class is considered a shardable linker. A linker is shardable if it either implements the Shardable annotation or it has a field named gwtIsShardable. If such a field is present, it doesn't matter what value the field holds. The latter mechanism is only intended to support linkers that must compile against older versions of GWT.

link

public ArtifactSet link(TreeLogger logger,
                        LinkerContext context,
                        ArtifactSet artifacts)
                 throws UnableToCompleteException

This method is invoked for linkers not annotated with Shardable. It sees all artifacts across the whole compile and can modify them arbitrarily. This method is only called if the linker is not annotated with Shardable.

Parameters:

logger - the TreeLogger to record to

context - provides access to the Linker's environment

artifacts - an unmodifiable view of the artifacts to link

Returns:

the artifacts that should be propagated through the linker chain

Throws:

UnableToCompleteException - if compilation violates assumptions made by the Linker or for errors encountered by the Linker

link

public ArtifactSet link(TreeLogger logger,
                        LinkerContext context,
                        ArtifactSet artifacts,
                        boolean onePermutation)
                 throws UnableToCompleteException

This method is invoked for linkers annotated with Shardable. It is called at two points during compilation: after the compile of each permutation, and after all compilation has finished. The onePermutation is true for a per-permutation call and false for a global final-link call.

For one-permutation calls, this method is passed all artifacts generated for just the one permutation. For the global call at the end of compilation, this method sees artifacts for the whole compilation, but with two modifications intended to support builds on computer clusters:

1. All EmittedArtifacts have been converted to BinaryEmittedArtifacts
2. All artifacts not marked as Transferable have been discarded.

Parameters:

logger - the TreeLogger to record to

context - provides access to the Linker's environment

artifacts - an unmodifiable view of the artifacts to link

onePermutation - true for a one-permutation call

Returns:

the artifacts that should be propagated through the linker chain

Throws:

UnableToCompleteException - if compilation violates assumptions made by the Linker or for errors encountered by the Linker

relink

public ArtifactSet relink(TreeLogger logger,
                          LinkerContext context,
                          ArtifactSet newArtifacts)
                   throws UnableToCompleteException

Re-invoke the Linker with newly generated artifacts. Linkers that need to reference the original artifact set passed into link(TreeLogger, LinkerContext, ArtifactSet) should retain a copy of the original artifact set in an instance variable.

Parameters:

logger - the TreeLogger to record to

context - provides access to the Linker's environment

newArtifacts - an unmodifiable view of the newly generated artifacts

Returns:

the new artifacts that should be propagated through the linker chain; it is not necessary to return any artifacts from the original link (or previous calls to relink) that have not been modified

Throws:

UnableToCompleteException - if compilation violates assumptions made by the Linker or for errors encountered by the Linker

supportsDevModeInJunit

public boolean supportsDevModeInJunit(LinkerContext context)

Returns true if this linker supports DevMode.

Parameters:

context - a LinkerContext