How to use JavaParser to add new methods to a parsing file? - javaparser

Question

I have parsed a java file and get the Compilation Unit
CompilationUnit
cu = JavaParser.parse(in); in a java file
How can I add some new methods by using this cu?
I just want to add the new methods in my original class.

Answer 1

This is an example on how you can create a method and add it to your compilation unit:
// create the type declaration
ClassOrInterfaceDeclaration type = cu.addClass("GeneratedClass");
// create a method
EnumSet<Modifier> modifiers = EnumSet.of(Modifier.PUBLIC);
MethodDeclaration method = new MethodDeclaration(modifiers, new VoidType(), "main");
modifiers.add(Modifier.STATIC);
method.setModifiers(modifiers);
type.addMember(method);
// or a shortcut
MethodDeclaration main2 = type.addMethod("main2", Modifier.PUBLIC, Modifier.STATIC);
// add a parameter to the method
Parameter param = new Parameter(new ClassOrInterfaceType("String"), "args");
param.setVarArgs(true);
method.addParameter(param);
// or a shortcut
main2.addAndGetParameter(String.class, "args").setVarArgs(true);
// 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");
call.addArgument(new StringLiteralExpr("Hello World!"));
block.addStatement(call);

Answer 2

here i am adding a new test method to some testing classes:
for (Node childNode : compilationUnit.getChildNodes()) {
if (childNode instanceof ClassOrInterfaceDeclaration) {
ClassOrInterfaceDeclaration classOrInterfaceDeclaration = (ClassOrInterfaceDeclaration) childNode;
MethodDeclaration method = classOrInterfaceDeclaration.addMethod("testingGetterAndSetter", Modifier.PUBLIC);
method.addMarkerAnnotation("Test");
NodeList<Statement> statements = new NodeList<>();
BlockStmt blockStmt = JavaParser.parseBlock(String.format(TestMethod, className));
method.setBody(blockStmt);
}
}
the Testmethod contains the body of the method

Answer 3

An example of creating a class with annotation and adding a method to that class is as follows.
ClassOrInterfaceDeclaration controllerClass = cu.addClass("SomeClass")
.setPublic(true)
.addAnnotation(org.springframework.web.bind.annotation.RestController.class);
MethodDeclaration indexMethod = controllerClass.addMethod("index", Keyword.PUBLIC);