java 复制对象有哪些方式
Apache的 Common beanutils库
org.apache.commons.beanutils.BeanUtils.copyProperties(dest,origin);
Springframework 的BeanUtil
依赖:
org.springframework
spring-beans
${spring.version}
BeanUtils.copyProperties(source, target);
Object 流
使用 ObjectInputStream
/**
* This method makes a "deep clone" of any Java object it is given.
*/
public static Object deepClone(Object object) {
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(object);
ByteArrayInputStream bais = new ByteArrayInputStream(
baos.toByteArray());
ObjectInputStream ois = new ObjectInputStream(bais);
return ois.readObject();
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
or
/**
* Returns a copy of the object, or null if the object cannot be serialized.
* refre:http://javatechniques.com/blog/faster-deep-copies-of-java-objects/
*/
public static Object copy(Object orig) {
Object obj = null;
try {
// Write the object out to a byte array
FastByteArrayOutputStream fbos = new FastByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream(fbos);
out.writeObject(orig);
out.flush();
out.close();
// Retrieve an input stream from the byte array and read
// a copy of the object back in.
ObjectInputStream in = new ObjectInputStream(fbos.getInputStream());
obj = in.readObject();
in.close();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException cnfe) {
cnfe.printStackTrace();
}
return obj;
}
json序列化
先序列化对象 为json;
然后对该json字符串 反序列化为新的对象.
/***
* 2018/7/18
*/
@Test
public final void test_CopyObject() {
Student student = new Student();
student.setName("liuyu");
System.out.println("复制前 :" +student.hashCode());
String json = HWJacksonUtils.getJsonP(student);
Student student2 = (Student)HWJacksonUtils.deSerialize(json, Student.class);
System.out.println("student2 :" + student2.getName());
System.out.println("复制后 :" +student2.hashCode());
}
使用开源库 DozerBeanMapperBuilder
依赖:
com.github.dozermapper
dozer-core
6.2.0
测试代码:
@Test
public final void test_Dozer() {
Student student = new Student();
student.setName("liuyu2");
Mapper instance = DozerBeanMapperBuilder.buildDefault();
Student student2 = instance.map(student, Student.class);
System.out.println("student2 :" + student2.getName());
}
FastByteArrayOutputStream 源码
package com.io.hw.file.util;
import java.io.InputStream;
import java.io.OutputStream;
/***
* refre:http://javatechniques.com/blog/faster-deep-copies-of-java-objects/
* ByteArrayOutputStream implementation that doesn't synchronize methods
* and doesn't copy the data on toByteArray().
*
* @author huangwei
* @since 2015年3月5日
*/
public class FastByteArrayOutputStream extends OutputStream {
/**
* Buffer and size
*/
protected byte[] buf = null;
protected int size = 0;
/**
* Constructs a stream with buffer capacity size 5K
*/
public FastByteArrayOutputStream() {
this(5 * 1024);
}
/**
* Constructs a stream with the given initial size
*/
public FastByteArrayOutputStream(int initSize) {
this.size = 0;
this.buf = new byte[initSize];
}
/**
* Ensures that we have a large enough buffer for the given size.
*/
private void verifyBufferSize(int sz) {
if (sz > buf.length) {
byte[] old = buf;
buf = new byte[Math.max(sz, 2 * buf.length)];
System.arraycopy(old, 0, buf, 0, old.length);
old = null;
}
}
public int getSize() {
return size;
}
/**
* Returns the byte array containing the written data. Note that this
* array will almost always be larger than the amount of data actually
* written.
*/
public byte[] getByteArray() {
return buf;
}
public final void write(byte b[]) {
verifyBufferSize(size + b.length);
System.arraycopy(b, 0, buf, size, b.length);
size += b.length;
}
public final void write(byte b[], int off, int len) {
verifyBufferSize(size + len);
System.arraycopy(b, off, buf, size, len);
size += len;
}
public final void write(int b) {
verifyBufferSize(size + 1);
buf[size] = (byte) b;
size++;
}
public void reset() {
size = 0;
}
/**
* Returns a ByteArrayInputStream for reading back the written data
*/
public InputStream getInputStream() {
return new FastByteArrayInputStream(buf, size);
}
}