在使用缓存读取数据后修改发现缓存被修改。于是找了下复制对象的方法。
关于对象克隆
按我的理解，对象是包含引用+数据。通常变量复制都是将引用传递过去。比如：
Person p1 = new Person();
Person p2 = p1;
这两句话，创建两个引用p1，p2，但指向共同的内存大堆数据。修改任何一个，另一个的数据也将修改。
直接引用传递测试用例：
1.实体类：
package com.test.java; import java.io.Serializable; /**
* Created by Administrator on 2015/9/16.
*/
public class Person implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
int id;
String name;
int age;
Country Country; @Override
public String toString() {
return "Person{" +
"id=" + id +
", name='" + name + '\'' +
", age=" + age +
", Country=" + Country +
", hashcode=" + hashCode() +
'}';
} public Person() {
} public Person(Country country, int id, String name) {
Country = country;
this.id = id;
this.name = name;
} public int getId() {
return id;
} public void setId(int id) {
this.id = id;
} public String getName() {
return name;
} public void setName(String name) {
this.name = name;
} public int getAge() {
return age;
} public void setAge(int age) {
this.age = age;
} public com.test.java.Country getCountry() {
return Country;
} public void setCountry(com.test.java.Country Country) {
this.Country = Country;
} public Person(String name,int age){ this.name=name;
this.age=age;
}
} class Country implements Serializable{
/**
*
*/
private static final long serialVersionUID = 1L;
int code;
String name; public Country() {
} public Country(int code) {
this.code = code;
} public Country(int code, String name) {
this.code = code;
this.name = name;
} public int getCode() {
return code;
} public void setCode(int code) {
this.code = code;
} public String getName() {
return name;
} public void setName(String name) {
this.name = name;
} @Override
public String toString() {
return "Country{" +
"code=" + code +
", name='" + name + '\'' +
", hashcode='" + hashCode() + '\'' +
'}';
}
}
2.测试类
package com.test.java; /**
* Created by Administrator on 2015/11/26.
* 测试对象引用
*/
public class TestRef { public static void main(String[] args) {
Country country = new Country(1,"china");
Person person = new Person(country,1,"test"); Country country1 = country;
Person person1 = person; System.out.println("创建国家 ："+country);
System.out.println("引用传递国家 ："+country1);
System.out.println("创建人 ："+person);
System.out.println("引用传递创建人："+person1); } }
3.打印结果：
4.分析：
通过hashcode可以证明，数据实体的地址是相同的。关于基本类型和引用类型的内存关系，可以参考这篇。
同样，通过实现clone接口，重载clone方法，然后调用person.clone()来复制对象的浅克隆是一样。参考这篇。
当然，采用深度克隆的话就可以生成两个完全不同的对象。
然而，我们创建的实体通常是不会实现和覆盖clone的，这种办法只能提前写好对应的类才可以实现。因此，不推荐使用。
那么，我们可以通过反射或者序列化来实现。
关于序列化
参考博客，Java序列化是指把Java对象转换为字节序列的过程；而Java反序列化是指把字节序列恢复为Java对象的过程。字节码可以存储，无状态，而对象在内存中开辟空间，有地址。
由此，可以把对象序列化后反序列化。相当于破碎重组。
前提是：实体类需要实现序列化接口
1.序列化实现对象复制
// 用序列化与反序列化实现深克隆
public static Object cloneBySer(Object baseObj) {
Object o = null;
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(baseObj);
oos.close();
ByteArrayInputStream bais = new ByteArrayInputStream(baos
.toByteArray());
ObjectInputStream ois = new ObjectInputStream(bais);
o = ois.readObject();
ois.close();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
return o;
}
2.测试用例：
public static void main(String[] args) {
Country country = new Country(1,"china");
Person person = new Person(country,1,"test");
//引用传递
Country country1 = country;
Person person1 = person;
//序列化和反序列化
Object person2 = ObjectCopy.cloneBySer(person);
Object country2 = ObjectCopy.cloneBySer(country);
// person.setAge(12);
System.out.println("创建国家 ："+country);
System.out.println("引用传递国家 ："+country1);
System.out.println("序列化复制国家 ："+country2);
System.out.println("创建人 ："+person);
System.out.println("引用传递人："+person1);
System.out.println("序列化复制人："+person2);
}
3.控制台打印：
4.分析
序列化完全实现了对象拷贝。要求：对象都实现序列化，对象hashcode和equals方法默认或者包含全部信息。
通过反射
反射可以复制一个对象的属性，从而实现对象拷贝
反射代码：
/**
* COPY对象(毛病还是很多的。。)
*对基本类型的过滤
* @author Lv9
* @since 2010.03.09
* baseObject 要拷贝的对象
* noCopyClassNames 不深度拷贝的对象属性
*/
public static Object coloneByRef(Object baseObject,
String... noCopyClassNames) throws Exception {
Object copyObject = baseObject.getClass().newInstance();
Field[] fields = baseObject.getClass().getDeclaredFields();
for (Field field : fields) {
field.setAccessible(true);
if (checkClassType(field.getType().getName(), noCopyClassNames)) {
field.set(copyObject, field.get(baseObject));
} else {
field.set(copyObject, coloneByRef(field.get(baseObject),
noCopyClassNames));
}
}
return copyObject;
} public static boolean checkClassType(String className,
String[] noCopyClassNames) {
for (String noCopyClassName : noCopyClassNames) {
if (className.equals(noCopyClassName)) {
return true;
}
}
return false;
}
一个失败的用例：
反射用的不太会
package com.test.reflect; import java.io.*;
import java.lang.reflect.Field; /**
* Created by Administrator on 2015/11/25.
* 对象复制
*/
public class ObjectCopy { public static void main(String[] args) throws Exception {
A baseObject = new A(new B(new C("bString1", "bString2"), 1, 2), new C(
"cString1", "cString2"));
A copyObject = (A) coloneByRef(baseObject, "java.lang.Integer",
"java.lang.String"); System.out.println(baseObject);
System.out.println(copyObject);
System.out.println("===================分割线===================");
System.out.println("原对象修改前："+baseObject);
A a = (A)cloneBySer(baseObject);
System.out.println("复制对象 ："+a);
a.setC(new C("cchange1","cchange2"));
System.out.println("复制后修改对象："+a);
System.out.println("原对象修改后 ："+baseObject); } /**
* COPY对象(毛病还是很多的。。)
*对基本类型的过滤
* @author Lv9
* @since 2010.03.09
* baseObject 要拷贝的对象
* noCopyClassNames 不深度拷贝的对象属性
*/
public static Object coloneByRef(Object baseObject,
String... noCopyClassNames) throws Exception {
Object copyObject = baseObject.getClass().newInstance();
Field[] fields = baseObject.getClass().getDeclaredFields();
for (Field field : fields) {
field.setAccessible(true);
if (checkClassType(field.getType().getName(), noCopyClassNames)) {
field.set(copyObject, field.get(baseObject));
} else {
field.set(copyObject, coloneByRef(field.get(baseObject),
noCopyClassNames));
}
}
return copyObject;
} public static boolean checkClassType(String className,
String[] noCopyClassNames) {
for (String noCopyClassName : noCopyClassNames) {
if (className.equals(noCopyClassName)) {
return true;
}
}
return false;
} // 用序列化与反序列化实现深克隆
public static Object cloneBySer(Object baseObj) {
Object o = null;
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(baos);
oos.writeObject(baseObj);
oos.close();
ByteArrayInputStream bais = new ByteArrayInputStream(baos
.toByteArray());
ObjectInputStream ois = new ObjectInputStream(bais);
o = ois.readObject();
ois.close();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
return o;
}
} class A implements Serializable{
/**
*
*/
private B b;
private C c; public A() { } public A(B b, C c) {
this.b = b;
this.c = c;
} public B getB() {
return b;
} public void setB(B b) {
this.b = b;
} public C getC() {
return c;
} public void setC(C c) {
this.c = c;
} @Override
public String toString() {
return "A{" +
" b=" + b +
", c=" + c +
'}';
}
} class B implements Serializable{
/**
*
*/
private C c;
private Integer int1;
private Integer int2; public B() { } public B(C c, Integer int1, Integer int2) {
this.c = c;
this.int1 = int1;
this.int2 = int2;
} public C getC() {
return c;
} public void setC(C c) {
this.c = c;
} public Integer getInt1() {
return int1;
} public void setInt1(Integer int1) {
this.int1 = int1;
} public Integer getInt2() {
return int2;
} public void setInt2(Integer int2) {
this.int2 = int2;
} @Override
public String toString() {
return "[B: int1 = " + int1 + ",int2 = " + int2 + ",c = " + c
+ ",hashCode = " + hashCode() + "]";
}
} class C implements Serializable{
/**
*
*/
private String string1;
private String string2; public C() { } public C(String string1, String string2) {
this.string1 = string1;
this.string2 = string2;
} public String getString1() {
return string1;
} public void setString1(String string1) {
this.string1 = string1;
} public String getString2() {
return string2;
} public void setString2(String string2) {
this.string2 = string2;
} @Override
public String toString() {
return "[C: string1 = " + string1 + ",string2 = " + string2
+ ",hashCode = " + hashCode() + "]";
}
}