【轉載】java 複製對象有哪些方式

原文地址：https://my.oschina.net/huangweiindex/blog/1858700

 

java 複製對象有哪些方式

 

Apache的 Common beanutils庫

org.apache.commons.beanutils.BeanUtils.copyProperties(dest,origin);

Springframework 的BeanUtil

依賴:

<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 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

先序列化對象 爲json;
而後對該json字符串 反序列化爲新的對象.

/*** * 2018/7/18 */ @Test public final void test_CopyObject() { Student student = new Student(); student.setName("liuyu"); System.out.println("複製前 :" +student.hashCode()); String json = HWJacksonUtils.getJsonP(student); Student student2 = (Student)HWJacksonUtils.deSerialize(json, Student.class); System.out.println("student2 :" + student2.getName()); System.out.println("複製後 :" +student2.hashCode()); } 

使用開源庫 DozerBeanMapperBuilder

依賴:

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

測試代碼:

@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 源碼

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); } } 

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