JDK的Parser来解析Java源代码详解

public class JavaParser {
 
 private static final String path = "User.java";
 
 private JavacFileManager fileManager;
 private JavacTool javacTool;
 
 public JavaParser() {
  Context context = new Context();
  fileManager = new JavacFileManager(context, true, Charset.defaultCharset());
  javacTool = new JavacTool();
 }
 
 public void parseJavaFiles() {
  Iterable<!--? extends JavaFileObject--> files = fileManager.getJavaFileObjects(path);
  JavaCompiler.CompilationTask compilationTask = javacTool.getTask(null, fileManager, null, null, null, files);
  JavacTask javacTask = (JavacTask) compilationTask;
  try {
   Iterable<!--? extends CompilationUnitTree--> result = javacTask.parse();
   for (CompilationUnitTree tree : result) {
    tree.accept(new SourceVisitor(), null);
 
   }
  } catch (IOException e) {
   e.printStackTrace();
  }
 }
 
 static class SourceVisitor extends TreeScanner<void, void=""> {
 
  private String currentPackageName = null;
 
  @Override
  public Void visitCompilationUnit(CompilationUnitTree node, Void aVoid) {  
   return super.visitCompilationUnit(node, aVoid);
  }
 
  @Override
  public Void visitVariable(VariableTree node, Void aVoid) {
   formatPtrln("variable name: %s, type: %s, kind: %s, package: %s", 
     node.getName(), node.getType(), node.getKind(), currentPackageName);
   return null;
  }
 }
 
 public static void formatPtrln(String format, Object... args) {
  System.out.println(String.format(format, args));
 }
 
 public static void main(String[] args) {
 
  new JavaParser().parseJavaFiles();
 }
}</void,>

package com.ragnarok.javaparser;
 
import com.sun.istack.internal.Nullable;
import java.lang.Override;
 
public class User {
 
 @Nullable
 private String foo = "123123";
 private Foo a;
 
 public void UserMethod() {}
 
 static class Foo {
  private String fooString = "123123";
 
  public void FooMethod() {}
 }
}

variable: foo, annotaion: Nullable
variable name: foo, type: String, kind: VARIABLE, package: com.ragnarok.javaparser
variable name: a, type: Foo, kind: VARIABLE, package: com.ragnarok.javaparser

@Override
public Void visitClass(ClassTree node, Void aVoid) {
 formatPtrln("class name: %s", node.getSimpleName());
 for (Tree member : node.getMembers()) {
  if (member instanceof VariableTree) {
   VariableTree variable = (VariableTree) member;
   List<!--? extends AnnotationTree--> annotations = variable.getModifiers().getAnnotations();
   if (annotations.size() > 0) {
    formatPtrln("variable: %s, annotaion: %s", variable.getName(), annotations.get(0).getAnnotationType());
   } else {
    formatPtrln("variable: %s", variable.getName());
   }    
  }
 }
 return super.visitClass(node, aVoid);
 }

class name: User
variable: foo, annotaion: Nullable
variable: a
class name: Foo
variable: fooString