使用JavaParser进行java源码解析

  JavaParser下载地址：http://code.google.com/p/javaparser/downloads/list

  刚开始接触的时候觉得和JDT里的Parser类不太一样。查了一下WiKi，发现它访问编译单元成员，需要调用相应子元素对应的Visitor类的visit（）方法。此方法可以通过复写来实现自己需要的功能。我需要的功能是将编译单元里的所有MethodDeclaration取出，因此利用传递句柄的方式，实现代码如下：

  

public static List<MethodDeclaration> getMethodList(CompilationUnit cu) {
        List<MethodDeclaration> methodList = new ArrayList<MethodDeclaration>();
        new MethodGetterVisitor().visit(cu, methodList);
        
        return methodList;
    }
    
    private static class MethodGetterVisitor extends VoidVisitorAdapter<Object> {

        @SuppressWarnings("unchecked")
        @Override
        public void visit(MethodDeclaration n, Object arg) {
            List<MethodDeclaration> methodList = new ArrayList<MethodDeclaration>();
            methodList =  (List<MethodDeclaration>) arg;
            methodList.add(n);
        }
    }

   

  官方还提供了不通过Visitor改变一个类成员方法的示例（相对Visitor更复杂）：

public class MethodChanger {

    public static void main(String[] args) throws Exception {
        // creates an input stream for the file to be parsed
        FileInputStream in = new FileInputStream("test.java");

        CompilationUnit cu;
        try {
            // parse the file
            cu = JavaParser.parse(in);
        } finally {
            in.close();
        }

        // change the methods names and parameters
        changeMethods(cu);

        // prints the changed compilation unit
        System.out.println(cu.toString());
    }

    private static void changeMethods(CompilationUnit cu) {
        List<TypeDeclaration> types = cu.getTypes();
        for (TypeDeclaration type : types) {
            List<BodyDeclaration> members = type.getMembers();
            for (BodyDeclaration member : members) {
                if (member instanceof MethodDeclaration) {
                    MethodDeclaration method = (MethodDeclaration) member;
                    changeMethod(method);
                }
            }
        }
    }

    private static void changeMethod(MethodDeclaration n) {
        // change the name of the method to upper case
        n.setName(n.getName().toUpperCase());

        // create the new parameter
        Parameter newArg = ASTHelper.createParameter(ASTHelper.INT_TYPE, "value");

        // add the parameter to the method
        ASTHelper.addParameter(n, newArg);
    }
}

 

 最后附上WiKi里给出的编译单元创建示例：

public class ClassCreator {

    public static void main(String[] args) throws Exception {
        // creates the compilation unit
        CompilationUnit cu = createCU();

        // prints the created compilation unit
        System.out.println(cu.toString());
    }

    /**
     * creates the compilation unit
     */
    private static CompilationUnit createCU() {
        CompilationUnit cu = new CompilationUnit();
        // set the package
        cu.setPakage(new PackageDeclaration(ASTHelper.createNameExpr("java.parser.test")));

        // create the type declaration 
        ClassOrInterfaceDeclaration type = new ClassOrInterfaceDeclaration(ModifierSet.PUBLIC, false, "GeneratedClass");
        ASTHelper.addTypeDeclaration(cu, type);

        // create a method
        MethodDeclaration method = new MethodDeclaration(ModifierSet.PUBLIC, ASTHelper.VOID_TYPE, "main");
        method.setModifiers(ModifierSet.addModifier(method.getModifiers(), ModifierSet.STATIC));
        ASTHelper.addMember(type, method);

        // add a parameter to the method
        Parameter param = ASTHelper.createParameter(ASTHelper.createReferenceType("String", 0), "args");
        param.setVarArgs(true);
        ASTHelper.addParameter(method, param);

        // add a body to the method
        BlockStmt block = new BlockStmt();
        method.setBody(block);

        // add a statement do the method body
        NameExpr clazz = new NameExpr("System");
        FieldAccessExpr field = new FieldAccessExpr(clazz, "out");
        MethodCallExpr call = new MethodCallExpr(field, "println");
        ASTHelper.addArgument(call, new StringLiteralExpr("Hello World!"));
        ASTHelper.addStmt(block, call);

        return cu;
    }
}