jdt学习

转自：http://plutoluo.javaeye.com/blog/146281

JDT实际上是将Java代码构建成一个基于DOM结构的抽象语法树AST（Abstract Syntax Tree ）。代码中的每个部分都对应一个ASTNode，许多的ASTNode就构成了这个抽象的语法树。Java Class一般对应Compilation Unit node，该节点也是AST树上的顶点。创建一个AST如下：

java 代码

ASTParser parser = ASTParser.newParser(AST.JLS3);
parser.setSource("".toCharArray());
CompilationUnit unit = (CompilationUnit) parser.createAST(null);
unit.recordModifications();
AST ast = unit.getAST();

其中createAST，当parse需要较长时间时，可以采用createAST(new NullProgressMonitor())，否则直接传null即可。

recordModifications()用于记录节点的变动，比如修改、删除等，当需要对AST树进行变动操作时，必须要预先调用这个方法。

比较重要的是：一个AST树上的所有节点必须都属于该AST。不允许直接将其他AST树上的节点添加该AST树上。否则会抛出java.lang.IllegalArgumentException异常。须使用ASTNode.copySubtree(AST target, ASTNode node)返回一个目标树的深度拷贝，才能进行添加操作。例如:

java 代码

ASTParser parser = ASTParser.newParser(AST.JLS3);
parser.setSource("".toCharArray());
CompilationUnit targetRoot= (CompilationUnit) parser.createAST(null);
targetRoot.recordModifications();
parser.setSource("class T{}”".toCharArray());
CompilationUnit srcRoot= (CompilationUnit) parser.createAST(null);

//这是非法操作，两者的AST源不一样
targetRoot.types().add(srcRoot.types().get(0));

//这是合法操作
targetRoot.types().add(ASTNode.copySubtree(
targetRoot.getAST(), (ASTNode) srcRoot.types().get(0)));

//这是合法操作
targetRoot.types().add(targetRoot.getAST().newTypeDeclaration());

现把一些 Java代码生成对应的ASTNode方式列出来，供参考：

List 1 生成Package

// package astexplorer;

    
    
    
    

     
     
     
     java 代码
    
    
    
    

    
    
    
    
PackageDeclaration packageDeclaration = ast.newPackageDeclaration();
unit.setPackage(packageDeclaration);
packageDeclaration.setName(ast.newSimpleName("astexplorer"));

List 2 生成Import

// import org.eclipse.swt.SWT;

// import org.eclipse.swt.events.*;

// import org.eclipse.swt.graphics.*;

// import org.eclipse.swt.layout.*;

// import org.eclipse.swt.widgets.*;

    
    
    
    

     
     
     
     java 代码
    
    
    
    

    
    
    
    
for (int i = 0; i < IMPORTS.length; ++i) {
ImportDeclaration importDeclaration = ast.newImportDeclaration();
importDeclaration.setName(ast.newName(getSimpleNames(IMPORTS[i])));
if (IMPORTS[i].indexOf("*") > 0)
importDeclaration.setOnDemand(true);
else
importDeclaration.setOnDemand(false);

unit.imports().add(importDeclaration);
}

List 3 生成Class Declaration

// public class SampleComposite extends Composite 

java 代码

    
    
    
    
TypeDeclaration classType = ast.newTypeDeclaration();
classType.setInterface(false);
classType.setModifiers(Modifier.PUBLIC);
classType.setName(ast.newSimpleName("SampleComposite"));
classType.setSuperclass(ast.newSimpleName("Composite"));
unit.types().add(classType);

 List 4 生成Constructor Declaration
 
 // public SampleComposite(Composite parent,int style){}

java 代码

    
    
    
    
MethodDeclaration methodConstructor = ast.newMethodDeclaration();
methodConstructor.setConstructor(true);
methodConstructor.setModifiers(Modifier.PUBLIC);
methodConstructor.setName(ast.newSimpleName("SampleComposite"));
classType.bodyDeclarations().add(methodConstructor);

// constructor parameters

SingleVariableDeclaration variableDeclaration = ast.newSingleVariableDeclaration();
variableDeclaration.setModifiers(Modifier.NONE);
variableDeclaration.setType(ast.newSimpleType(ast.newSimpleName("Composite")));
variableDeclaration.setName(ast.newSimpleName("parent"));
methodConstructor.parameters().add(variableDeclaration);

variableDeclaration = ast.newSingleVariableDeclaration();
variableDeclaration.setModifiers(Modifier.NONE);
variableDeclaration.setType(ast.newPrimitiveType(PrimitiveType.INT));
variableDeclaration.setName(ast.newSimpleName("style"));
methodConstructor.parameters().add(variableDeclaration);

Block constructorBlock = ast.newBlock();
methodConstructor.setBody(constructorBlock);

 List 5 生成Spuer Invocation
 
 // super(parent,style)

java 代码

     
    
    
    
SuperConstructorInvocation superConstructorInvocation = ast.newSuperConstructorInvocation();
constructorBlock.statements().add(superConstructorInvocation);
Expression exp = ast.newSimpleName("parent");
superConstructorInvocation.arguments().add(exp);
superConstructorInvocation.arguments().add(ast.newSimpleName("style"));

List 6 生成ClassInstanceCreation
 
 // GridLayout gridLayout = new GridLayout();

java 代码

     
    
    
    
VariableDeclarationFragment vdf = ast.newVariableDeclarationFragment();
vdf.setName(ast.newSimpleName("gridLayout"));
ClassInstanceCreation cc = ast.newClassInstanceCreation();
cc.setName(ast.newSimpleName("GridLayout"));
vdf.setInitializer(cc);
VariableDeclarationStatement vds = ast.newVariableDeclarationStatement(vdf);
vds.setType(ast.newSimpleType(ast.newSimpleName("GridLayout")));
constructBlock.statements().add(vds);

// Label label = new Label(this,SWT.NONE);

java 代码

     
    
    
    
VariableDeclarationFragment vdf = ast.newVariableDeclarationFragment();
vdf.setName(ast.newSimpleName("label"));
cc = ast.newClassInstanceCreation();
cc.setName(ast.newSimpleName("Label"));
cc.arguments().add(ast.newThisExpression());
cc.arguments().add(ast.newName(getSimpleNames("SWT.NONE")));
vdf.setInitializer(cc);
VariableDeclarationStatement vds = ast.newVariableDeclarationStatement(vdf);
vds.setType(ast.newSimpleType(ast.newSimpleName("Label")));
constructBlock.statements().add(vds);

List 7生成MethodInvocation
 
 // setLayout(gridLayout);

java 代码

    
    
    
    
MethodInvocation mi = ast.newMethodInvocation();
mi.setName(ast.newSimpleName("setLayout"));
mi.arguments().add(ast.newSimpleName("gridLayout"));
constructorBlock.statements().add(ast.newExpressionStatement(mi));

// label.setText("Press the button to close:");

        java 代码

    
    
    
    
mi = ast.newMethodInvocation();
mi.setExpression(ast.newSimpleName("label"));
mi.setName(ast.newSimpleName("setText"));
StringLiteral sl = ast.newStringLiteral();
sl.setLiteralValue("Press the button to close:");
mi.arguments().add(sl);
constructorBlock.statements().add(ast.newExpressionStatement(mi));

// label.setLayoutData(new GridData(GridData.HORIZONTAL_ALIGN_CENTER));

           java 代码

     
     
     
     
mi = ast.newMethodInvocation();
mi.setExpression(ast.newSimpleName("label"));
mi.setName(ast.newSimpleName("setLayoutData"));

cc = ast.newClassInstanceCreation();
cc.setName(ast.newSimpleName("GridData"));
cc.arguments().add(ast.newName(getSimpleNames("GridData.HORIZONTAL_ALIGN_CENTER")));
mi.arguments().add(cc);
constructorBlock.statements().add(ast.newExpressionStatement(mi));


 // Button button = new Button(this,SWT.PUSH);

    
    
    
    

     
     
     
     java 代码
    
    
    
    

    
    
    
    
vdf = ast.newVariableDeclarationFragment();
vdf.setName(ast.newSimpleName("button"));
vds = ast.newVariableDeclarationStatement(vdf);
vds.setType(ast.newSimpleType(ast.newSimpleName("Button")));
constructorBlock.statements().add(vds);

cc = ast.newClassInstanceCreation();
cc.setName(ast.newSimpleName("Button"));
vdf.setInitializer(cc);
cc.arguments().add(ast.newThisExpression());
cc.arguments().add(ast.newName(getSimpleNames("SWT.PUSH")));

// button.addSelectionListener(new SelectionAdapter() {}); 
    java 代码

    
    
    
    
mi = ast.newMethodInvocation();
constructorBlock.statements().add(ast.newExpressionStatement(mi));
mi.setExpression(ast.newSimpleName("button"));
mi.setName(ast.newSimpleName("addSelectionListener"));

ClassInstanceCreation ci = ast.newClassInstanceCreation();
ci.setName(ast.newSimpleName("SelectionAdapter"));
mi.arguments().add(ci);
AnonymousClassDeclaration cd = ast.newAnonymousClassDeclaration();
ci.setAnonymousClassDeclaration(cd);