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:

 <dependency><groupId>org.springframework</groupId><artifactId>spring-beans</artifactId><version>${spring.version}</version></dependency>

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.<br>* 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 arrayFastByteArrayOutputStream 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*/@Testpublic 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:

  <dependency><groupId>com.github.dozermapper</groupId><artifactId>dozer-core</artifactId><version>6.2.0</version></dependency>

测试代码:

 @Testpublic 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/<br>* 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);}
}

参考:
https://github.com/DozerMapper/dozer