使用Eclipse AST来解析Java

Eclipse中有个Outline视图，这个视图内可以显示类的各种信息，包括属性、方法等。同时在这个视图内点击哪里，就能定位的类什么地方。这是个神奇的东西，那么它是如何实现的呢？其实就是AST（Abstract Syntax Tree），抽象语法树了。利用这个来对Java源码进行解析。
另外，Eclipse有一个AST View插件，使用这个能更加的清楚的看到解析后的效果。

依赖的jar包

• org.eclipse.core.contenttype_3.4.100.v20110423-0524.jar
• org.eclipse.core.jobs_3.5.101.v20120113-1953.jar
• org.eclipse.core.resources_3.7.101.v20120125-1505.jar
• org.eclipse.core.runtime_3.7.0.v20110110.jar
• org.eclipse.equinox.common_3.6.0.v20110523.jar
• org.eclipse.equinox.preferences_3.4.2.v20120111-2020.jar
• org.eclipse.jdt.core_3.7.3.v20120119-1537.jar
• org.eclipse.osgi_3.7.2.v20120110-1415.jar

这些包都可以在eclipse的plugin目录找到。可能版本有所区别。
如果使用maven管理，经个人试验，直接使用以下dependency也是可以的。

<dependency>
      <groupId>org.eclipse.tycho</groupId>
      <artifactId>org.eclipse.jdt.core</artifactId>
      <version>3.8.0.v_C03</version>
  </dependency>
   <dependency>
       <groupId>org.eclipse.core</groupId>
       <artifactId>org.eclipse.core.runtime</artifactId>
       <version>3.6.0.v20100505</version>
   </dependency>
  <dependency>
      <groupId>org.eclipse.core</groupId>
      <artifactId>org.eclipse.core.resources</artifactId>
      <version>3.6.0.v20100526-0737</version>
  </dependency>

如何解析Java

package cn.shenyanchao.ast;

import org.apache.commons.io.FileUtils;
import org.eclipse.jdt.core.dom.*;

import java.io.File;
import java.io.IOException;
import java.util.List;

/**
 * Created with IntelliJ IDEA.
 *
 * @author shenyanchao
 *         Date:  6/13/13
 *         Time:  11:52 AM
 */
public class AstAnalyzer {
    public static void main(String[] args) throws IOException {

        String javaSource = FileUtils.readFileToString(new File("/home/shenyanchao/IdeaProjects/ast/src/main/java/cn/shenyanchao/from/ShenYanChaoAST.java"));

        ASTParser parser = ASTParser.newParser(AST.JLS3);
        parser.setSource(javaSource.toCharArray());

        // 使用解析器进行解析并返回AST上下文结果(CompilationUnit为根节点)
        CompilationUnit result = (CompilationUnit) parser.createAST(null);

        result.imports();
        result.getPackage();
        result.getCommentList();
        System.out.println(result.getCommentList().toString());

        TypeDeclaration type = (TypeDeclaration) result.types().get(0);
        System.out.println("---------Type---------");
        System.out.println(type.toString());

        MethodDeclaration method = type.getMethods()[0];
        method.parameters();
        method.isConstructor();

        System.out.println("---------Method---------");
        System.out.println(method.toString());
        method.getName();
        method.getModifiers();
        Type returnType = method.getReturnType2();
        System.out.println("returnType = " + returnType.toString());


        Block methodBody = method.getBody();
        List<Statement> statementList = methodBody.statements();

        System.out.println(statementList.toString());

        statementList.get(0);

        ExpressionStatement ifs = (ExpressionStatement) method.getBody().statements().get(1);
        Assignment expression = (Assignment) ifs.getExpression();
        Expression exp = expression.getRightHandSide();

        System.out.println(result.toString());
    }
}

如何创建Java

package cn.shenyanchao.ast;

import org.eclipse.jdt.core.dom.*;

/**
 * Created with IntelliJ IDEA.
 *
 * @author shenyanchao
 *         Date:  6/13/13
 *         Time:  11:27 AM
 */
public class AstHelloWorld {


    public static void main(String[] args) {
        AST ast = AST.newAST(AST.JLS3);
        CompilationUnit compilationUnit = ast.newCompilationUnit();

        // 创建类
        TypeDeclaration programClass = ast.newTypeDeclaration();
        programClass.setName(ast.newSimpleName("HelloWorld"));
        programClass.modifiers().add(
                ast.newModifier(Modifier.ModifierKeyword.PUBLIC_KEYWORD));
        compilationUnit.types().add(programClass);

        // 创建包
        PackageDeclaration packageDeclaration = ast.newPackageDeclaration();
        packageDeclaration.setName(ast.newName("cn.shenyanchao.hello"));
        compilationUnit.setPackage(packageDeclaration);

        MethodDeclaration main = ast.newMethodDeclaration();
        main.setName(ast.newSimpleName("main"));
        main.modifiers().add(
                ast.newModifier(Modifier.ModifierKeyword.PUBLIC_KEYWORD));
        main.modifiers().add(ast.newModifier(Modifier.ModifierKeyword.STATIC_KEYWORD));
        main.setReturnType2(ast.newPrimitiveType(PrimitiveType.VOID));
        programClass.bodyDeclarations().add(main);
        Block mainBlock = ast.newBlock();
        main.setBody(mainBlock);

        // 给main方法定义String[]参数
        SingleVariableDeclaration mainParameter = ast
                .newSingleVariableDeclaration();
        mainParameter.setName(ast.newSimpleName("arg"));
        mainParameter.setType(ast.newArrayType(ast.newSimpleType(ast
                .newName("String"))));
        main.parameters().add(mainParameter);

        MethodInvocation println = ast.newMethodInvocation();
        println.setName(ast.newSimpleName("println"));

        //生成String类型的常量
        StringLiteral s = ast.newStringLiteral();
        s.setLiteralValue("Hello World");
        println.arguments().add(s);

        println.setExpression(ast.newName("System.out"));

        mainBlock.statements().add(ast.newExpressionStatement(println));

        System.out.println(compilationUnit.toString());
    }
}

具体的使用手册，参见http://www.shenyanchao.cn/blog/2013/06/07/eclipse-ast/