请教:如何根据字符串中的内容创建对象

Question

public class CreateObj {
public Object createObj(){
String objName = "Person";
Map fieldMap = new HashMap();
fieldMap.put("name", "java.lang.String");
fieldMap.put("age", "int");
return null;
}
}

上面这个类中的createObj方法能根据 objName和filedMap中的值创建一个和
public class Person {
private String name;
private int age;
}
Person person1 = new Person();
相同的对象?

Answer 1

[code="java"]
public Class build(String clsname,String savepath,Collection properties){
Class clz=null;
try {
String className = clsname.replace(".", "/");
// 创建类信息
ClassWriter cw = new ClassWriter(0);
//申明类名 以及 访问修饰符
cw.visit(V1_5, ACC_PUBLIC + ACC_SUPER, className, null, "java/lang/Object", null);
//建立构造函数
MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "", "()V", null, null);
mv.visitCode();
mv.visitVarInsn(ALOAD, 0);
mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "", "()V");
mv.visitInsn(RETURN);
mv.visitMaxs(1, 1);
mv.visitEnd();

        FiledInfo filed = null;
        String fileName = null;
        String fileType = null;

        Iterator iterator = properties.iterator();
        while(iterator.hasNext()){
            filed = (FiledInfo)iterator.next();
            fileName = WordUtils.capitalize(filed.getName());   // 首字母大写
            fileType = filed.getType().replace(".", "/");;
            //建立属性对应的类变量
            cw.visitField(ACC_PRIVATE, filed.getName(), "L"+fileType+";", null, null).visitEnd();
            // get方法
            mv=cw.visitMethod(ACC_PUBLIC, "get"+fileName, "()L"+fileType+";", null, null);
            mv.visitCode();
            mv.visitVarInsn(ALOAD, 0);
            mv.visitFieldInsn(GETFIELD, className, filed.getName(), "L"+fileType+";");
            mv.visitInsn(ARETURN);
            mv.visitMaxs(1, 1);
            mv.visitEnd();
            // set方法
            mv=cw.visitMethod(ACC_PUBLIC, "set"+fileName, "(L"+fileType+";)V", null, null);
            mv.visitCode();
            mv.visitVarInsn(ALOAD, 0);
            mv.visitVarInsn(ALOAD, 1);
            mv.visitFieldInsn(PUTFIELD, className, filed.getName(), "L"+fileType+";");
            mv.visitMaxs(2, 2);
            mv.visitInsn(RETURN);
            mv.visitEnd();
        }
        cw.visitEnd();
        // 输出class文件
        byte[] code=cw.toByteArray();
        if(savepath!=null){
            int pos = savepath.lastIndexOf("\\");
            String dir = savepath.substring(0,pos);
            File directory =new File(dir);
            if (!directory.exists())
                directory.mkdirs();
            File file = new File(savepath);
            if (file.exists()){
                file.createNewFile();
            }else{
                file.delete();
            }

            FileOutputStream fos = new FileOutputStream(file);
            fos.write(code);
            fos.close();
        }
        clz = this.defineClass(clsname, code, 0, code.length);
    } catch (Exception e) {
    }
    return clz;
}

[/code]
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