嵌入Groovy脚本时添加一些默认import
刚才给在做的项目里加了些便捷功能，把做法记下来。
我们在Java应用里嵌入了Groovy脚本。为了方便，业务里经常用的一些类可以默认import进来，让大家少写点重复代码。幸好，这种功能用Groovy来做毫不费力。
import groovy.lang.GroovyClassLoader;import java.security.CodeSource;import org.codehaus.groovy.ast.ClassHelper;import org.codehaus.groovy.ast.ModuleNode;import org.codehaus.groovy.control.CompilationFailedException;import org.codehaus.groovy.control.CompilationUnit;import org.codehaus.groovy.control.CompilerConfiguration;import org.codehaus.groovy.control.Phases;import org.codehaus.groovy.control.SourceUnit;import org.codehaus.groovy.control.CompilationUnit.SourceUnitOperation;public class CustomGroovyClassLoader extends GroovyClassLoader { private final String[] DEFAULT_IMPORT_CLASSES = { "rednaxelafx.sample.Foo", "rednaxelafx.sample.Bar" }; /** * Validate classes. * * Because the specified default import classes might not be present in * the during runtime, they have to be validated first, otherwise Groovy * won't compile the code. * * @param className the name of the class to validate * @return true iff the class exists and is valid */ private boolean isClassValid(String className) { try { loadClass(className, false); return true; } catch (ClassNotFoundException e) { return false; } } private static String getClassSimpleName(final String className) { return className.substring(className.lastIndexOf('.') + 1); } private static boolean alreadyImported(final String alias, final ModuleNode ast) { return ast.getImport(alias) != null; } /** * add default imports */ @Override protected CompilationUnit createCompilationUnit( CompilerConfiguration config, CodeSource source) { CompilationUnit compUnit = super.createCompilationUnit(config, source); compUnit.addPhaseOperation(new SourceUnitOperation() { public void call(SourceUnit source) throws CompilationFailedException { ModuleNode ast = source.getAST(); for (String className : DEFAULT_IMPORT_CLASSES) { String simpleClassName = getClassSimpleName(className); if (isClassValid(className) && !alreadyImported(simpleClassName, ast)) { ast.addImport(simpleClassName, ClassHelper.make(className)); } } } }, Phases.CONVERSION); return compUnit; }}