# JJTree Task

## JJTree

### Description

Invokes the JJTree preprocessor for the JavaCC compiler compiler. It inserts parse tree building actions at various places in the JavaCC source that it generates. The output of JJTree is run through JavaCC to create the parser.

To use the jjtree task, set the target attribute to the name of the jjtree grammar file to process. You also need to specify the directory containing the JavaCC installation using the javacchome attribute, so that ant can find the JavaCC classes. Optionally, you can also set the outputdirectory to write the generated file to a specific directory. Otherwise jjtree writes the generated JavaCC grammar file to the directory containing the JJTree grammar file.

This task only invokes JJTree if the grammar file is newer than the generated JavaCC file.

### Parameters

Attribute | Description | Required
target | The jjtree grammar file to process. | Yes
javacchome | The directory containing the JavaCC distribution. | Yes
outputdirectory | The directory to write the generated file to. If not set, the files are written to the directory containing the grammar file. | No
buildnodefiles | Sets the BUILD_NODE_FILES grammar option. This is a boolean option. | No
multi | Sets the MULTI grammar option. This is a boolean option. | No
nodedefaultvoid | Sets the NODE_DEFAULT_VOID grammar option. This is a boolean option. | No
nodefactory | Sets the NODE_FACTORY grammar option. This is boolean option. | No
nodescopehook | Sets the NODE_SCOPE_HOOK grammar option. This is a boolean option. | No
nodeusesparser | Sets the NODE_USES_PARSER grammar option. This is a boolean option. | No
static | Sets the STATIC grammar option. This is a boolean option. | No
visitor | Sets the VISITOR grammar option. This is a boolean option. | No
nodepackage | Sets the NODE_PACKAGE grammar option. This is a string option. | No
visitorexception | Sets the VISITOR_EXCEPTION grammar option. This is a string option. | No
nodeprefix | Sets the NODE_PREFIX grammar option. This is a string option. | No

### Example

>     <jjtree
>         target="src/Parser.jjt"
>         outputdirectory="build/src"
>         javacchome="c:/program files/JavaCC"
>         nodeusesparser="true"
>     />

This invokes JJTree on grammar file src/Parser.jjt, writing the generated grammar file, Parser.jj, file to build/src. The grammar option NODE_USES_PARSER is set to true when invoking JJTree.

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