Examples of org.drools.lang.Expander

org.drools.lang.Expander
Expanders are extension points for expanding expressions in DRL at parse time. This is just-in-time translation, or macro expansion, or whatever you want. The important thing is that it happens at the last possible moment, so any errors in expansion are included in the parsers errors. Just-in-time expansions may include complex pre-compilers, or just macros, and everything in between. Expanders should ideally not make presumptions on any embedded semantic language. For instance, java aware pre processing should be done in drools-java semantic module, not in the parser itself. Expanders should be reusable across semantic languages.

            resolver = new DefaultExpanderResolver( dsl );
        } catch ( final IOException e ) {
            throw new DroolsParserException( "Error parsing the DSL.",
                                             e );
        }
        final Expander expander = resolver.get( "*",
                                          null );
        final String expanded = expander.expand( source );
        
        if ( expander.hasErrors() ) {
            String err = "";
            for ( Iterator iter = expander.getErrors().iterator(); iter.hasNext(); ) {
                ExpanderException ex = (ExpanderException) iter.next();
                err  = err + "\n Line:[" + ex.getLine() + "] " + ex.getMessage();
                
            }
            throw new DroolsParserException(err);

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        }


        for (int index = 0; index < children.length; index++) {
            if (file.parseAndLoad(new StringReader(
                    loadResource(children[index])))) {
                final Expander expander = new DefaultExpander();
                expander.addDSLMapping(file.getMapping());
                resolver.addExpander("*", expander);
            } else {
                throw new RuntimeDroolsException(
                        "Error parsing and loading DSL file."
                                + file.getErrors());

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     * This is the constructor most people should use.
     */
    public DefaultExpanderResolver(final Reader reader) throws IOException {
        final DSLMappingFile file = new DSLMappingFile();
        if ( file.parseAndLoad( reader ) ) {
            final Expander expander = new DefaultExpander();
            expander.addDSLMapping( file.getMapping() );
            this.expanders.put( "*",
                                expander );
        } else {
            throw new RuntimeDroolsException( "Error parsing and loading DSL file." + file.getErrors() );
        }

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    public Expander get(final String name,
                        final String config) {
        if ( this.expanders.containsKey( name ) ) {
            return (Expander) this.expanders.get( name );
        } else {
            final Expander exp = (Expander) this.expanders.get( "*" );
            if ( exp == null ) {
                throw new IllegalArgumentException( "Unable to provide an expander for " + name + " or a default expander." );
            }
            return exp;
        }

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    public PackageDescr parse(final String source,
                              final Reader dsl) throws DroolsParserException {
      
      DefaultExpanderResolver resolver = getDefaultResolver(dsl);
      
        final Expander expander = resolver.get( "*",
                                          null );
        final String expanded = expander.expand( source );
        if ( expander.hasErrors() ) {
            this.results.addAll( expander.getErrors() );
        }
        return this.parse( expanded );
    }

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     * @param resolver - the DSL expander resolver itself.
     * @throws DroolsParserException If unable to expand in any way.
     */
    public String getExpandedDRL(final String source, final DefaultExpanderResolver resolver ) throws DroolsParserException {


      final Expander expander = resolver.get( "*",
                                          null );
        final String expanded = expander.expand( source );
        
        if ( expander.hasErrors() ) {
            String err = "";
            for ( Iterator iter = expander.getErrors().iterator(); iter.hasNext(); ) {
                ExpanderException ex = (ExpanderException) iter.next();
                err  = err + "\n Line:[" + ex.getLine() + "] " + ex.getMessage();
                
            }
            throw new DroolsParserException(err);

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        DefaultExpanderResolver resolver = new DefaultExpanderResolver(new StringReader(dsl));
        
        
        final DSLMappingFile file = new DSLTokenizedMappingFile();
        if ( file.parseAndLoad( new StringReader(dsl) ) ) {
            final Expander expander = new DefaultExpander();
            expander.addDSLMapping( file.getMapping() );
            resolver.addExpander("*", expander);
        } else {
            throw new RuntimeDroolsException( "Error parsing and loading DSL file." + file.getErrors() );
        }

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    public void testMultiLineTemplates() throws Exception {
        final Reader source = new InputStreamReader( getClass().getResourceAsStream( "rule_with_expander_multiline.dslr" ) );
        final Reader dsl = new InputStreamReader( getClass().getResourceAsStream( "test_dsl_multiline.dsl" ) );
        Expander ex =  new DefaultExpanderResolver(dsl).get("*", null);
        String r = ex.expand(source);
        assertEquals("when Car(color==\"Red\") then doSomething();", r.trim());
    }

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        DefaultExpanderResolver resolver = new DefaultExpanderResolver(new StringReader(dsl));
        
        
        final DSLMappingFile file = new DSLMappingFile();
        if ( file.parseAndLoad( new StringReader(dsl) ) ) {
            final Expander expander = new DefaultExpander();
            expander.addDSLMapping( file.getMapping() );
            resolver.addExpander("*", expander);
        } else {
            throw new RuntimeDroolsException( "Error parsing and loading DSL file." + file.getErrors() );
        }

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    public PackageDescr parse(boolean isEditor,
                              final String source,
                              final Reader dsl) throws DroolsParserException {
        DefaultExpanderResolver resolver = getDefaultResolver( dsl );


        final Expander expander = resolver.get( "*",
                                                null );
        final String expanded = expander.expand( source );
        if ( expander.hasErrors() ) {
            this.results.addAll( expander.getErrors() );
        }
        return this.parse( isEditor,
                           expanded );
    }

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Related Classes of org.drools.lang.Expander

org.drools.compiler.DrlParser

org.drools.compiler.DrlParserTest

org.drools.contrib.DroolsCompilerAntTask

org.drools.integrationtests.DslTest

org.drools.lang.dsl.DefaultExpanderResolver

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