① java 反射可以給對象添加方法和屬性嗎
添加方法和屬性,這相當於修改了這個class類型, 可以參考cglib之類的操作java位元組碼的技術。
② 怎麼給java對象添加動態添加屬性和方法
給某個對象動態不了屬性的
但是可以通過集合類來實現
例如你可以用Map這個類來實現
map.put(key,value);
鍵值對都是泛型
之後通過map.get(key);來獲取
③ java 關於子類怎麼添加自己新的屬性
//這樣行么?
abstract class Person {
String name;
int age;
String professional;
Person(String name,int age,String professional) {
this.name= name;
this.age = age;
this.professional=professional;
}
public abstract void display();
}
class Students extends Person {
int year;
Students(String n,int a,String p) {
super(n,a,p);
}
Students(String n,int a,String p,int year) {
super(n,a,p);
this.year = year;
}
public void display() {
System.out.println("我的姓名="+ name + " " + "我的年齡="+age +" " +"我的專業="+professional);
}
}
public class Test5 {
public static void main(String[] args) {
Person p = new Students("男",19,"美術");
Person o = new Students("女",14,"跳舞");
p.display();
o.display();
Person p1 = new Students("男",20,"軟體",1991);
}
}
④ java使用dom方法為節點添加屬性
在程序中寫
seed所對應的對象.addAttribute("abc","1");
該方法會在seed中添加一個屬性名是專abc
值是
1的屬性
//
使用addAttribute方法向journal元素添加title和屬publisher屬性
journalElement.addAttribute("title",
"XML
Zone");
journalElement.addAttribute("publisher",
"Willpower
Co");
⑤ java中如何在object中添加額外屬性
那是你類設計上的問題,加屬性繼承實現就是了
⑥ java如何在自動生成的實體類中添加屬性及其get、set方法
右鍵 選中source 然後getters setters 打開之後選中你需要添加的方法,finnish~
⑦ java 可以動態創建 屬性欄位么
可以的,你用 javassist, cglib 或者更為底層的工具 ASM 都是可以。
ASM 的話相對復雜一些,參考代碼:
下面這個是用 ASM 工具為 Student 類添加一個 public String 類型的 address 屬性:
1,需要添加屬性的原始類:Student.java
Java code?
public class Student {
private int age;
private String name;
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
2,添加屬性的適配器:AddFieldAdapter.java
Java code?
import org.objectweb.asm.ClassAdapter;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.FieldVisitor;
public class AddFieldAdapter extends ClassAdapter {
private int accessModifier;
private String name;
private String desc;
private boolean isFieldPresent;
public AddFieldAdapter(ClassVisitor cv, int accessModifier, String name, String desc) {
super(cv);
this.accessModifier = accessModifier;
this.name = name;
this.desc = desc;
}
@Override
public FieldVisitor visitField(int access, String name, String desc,
String signature, Object value) {
if (name.equals(this.name)) {
isFieldPresent = true;
}
return cv.visitField(access, name, desc, signature, value);
}
@Override
public void visitEnd() {
if (!isFieldPresent) {
FieldVisitor fv = cv.visitField(accessModifier, name, desc, null, null);
if (fv != null) {
fv.visitEnd();
}
}
cv.visitEnd();
}
}
3,添加屬性的工具 AddField.java
Java code?
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import org.objectweb.asm.ClassAdapter;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Opcodes;
public class AddField {
private Class clazz = null;
private ClassReader cr = null;
private ClassWriter cw = null;
private ClassAdapter ca = null;
private File classFile = null;
private final static String CLASS_FILE_SUFFIX = ".class";
public AddField(Class clazz) {
this.clazz = clazz;
}
/**
* 添加一個 public 的類成員
* @param fieldName 類成員名
* @param fieldDesc 類成員類型描述
*/
public void addPublicField(String fieldName, String fieldDesc) {
if(cr == null) {
try {
cr = new ClassReader(clazz.getCanonicalName());
} catch (IOException e) {
e.printStackTrace();
}
cw = new ClassWriter(cr, ClassWriter.COMPUTE_MAXS);
}
if(ca == null) {
ca = new AddFieldAdapter(cw, Opcodes.ACC_PUBLIC, fieldName, fieldDesc);
} else {
ca = new AddFieldAdapter(ca, Opcodes.ACC_PUBLIC, fieldName, fieldDesc);
}
}
/**
* 將位元組碼寫入類的 .class 文件
*
*/
public void writeByteCode() {
cr.accept(ca, ClassReader.SKIP_DEBUG);
byte[] bys = cw.toByteArray();
OutputStream os = null;
try {
os = new FileOutputStream(getFile());
os.write(bys);
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
* 獲得類文件的 File 對象
* @return
*/
private File getFile() {
if(classFile == null) {
StringBuffer sb = new StringBuffer();
sb.append(clazz.getResource("/"))
.append(clazz.getCanonicalName().replace(".", File.separator))
.append(CLASS_FILE_SUFFIX);
classFile = new File(sb.substring(6));
}
return classFile;
}
}
⑧ java 關於子類怎麼添加自己新的屬性
abstract class Person {
String name;
int age;
String professional;
Person(String name,int age,String professional) {
this.name= name;
this.age = age;
this.professional=professional;
}
public abstract void display();
}
class Students extends Person {
int year;
Students(String n,int a,String p,int year) {
super(n,a,p);
this.year=year;
}
public void display() {
System.out.println("我的姓名="+ name + " " + "我的年齡="+age +" " +"我的專業="+professional+"我的出生年為"+year);
}
}
public class Test5 {
public static void main(String[] args) {
Person p = new Students("男",19,"美術");
Person o = new Students("女",14,"跳舞");
p.display();
o.display();
}
}