Java序列化之開篇

一、概念 序列化：把對象轉換為位元組序列的過程 反序列化：把位元組序列恢複為對象的過程 二、用途 1、将對象持久化到實體硬碟上，通常檔案方式存在； 2、在網絡上傳輸對象的位元組序列。 三、試驗 例子中使用 java.io.ObjectOutputStream将對象進行序列化，使用 java.io.ObjectInputStream将對象進行反序列化。 1、普通java類未實作Serializable接口

測試實體類SmallDog.java

public class SmallDog { private String name; private Double weight; private int age; public SmallDog() { } public SmallDog(String name, Double weight, int age) { this.name = name; this.weight = weight; this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Double getWeight() { return weight; } public void setWeight(Double weight) { this.weight = weight; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } }

将SmallDog進行序列化代碼片段

public void testUnImplSeralizable(){ com.smalldog.unimplseralizable.SmallDog smallDog = new com.smalldog.unimplseralizable.SmallDog("小白", 4.0, 1); try { FileOutputStream fos = new FileOutputStream("unimplseralizable.txt"); ObjectOutputStream oos = new ObjectOutputStream(fos); oos.writeObject(smallDog); oos.flush(); oos.close(); } catch (IOException e) { e.printStackTrace(); } }

輸出結果

java.io.NotSerializableException: com.smalldog.unimplseralizable.SmallDog at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1183) at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347) at com.smalldog.SerializableTestCase.testUnImplSeralizable(SerializableTestCase.java:19) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20) at org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184) at org.junit.runners.ParentRunner.run(ParentRunner.java:236) at org.junit.runner.JUnitCore.run(JUnitCore.java:157) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:117) at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234) at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)

2、普通java類實作Serializable接口

測試實體類SmallDog.java （與以上例子增加了實作接口）

public class SmallDog implements Serializable{ private String name; private Double weight; private int age; public SmallDog() { } public SmallDog(String name, Double weight, int age) { this.name = name; this.weight = weight; this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Double getWeight() { return weight; } public void setWeight(Double weight) { this.weight = weight; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } @Override public String toString() { return "SmallDog{" + "name='" + name + '\'' + ", weight=" + weight + ", age=" + age + '}'; } }

将SmallDog進行序列化代碼片段

public void testSeralizableSmallDog(){ SmallDog smallDog = new SmallDog("小白", 4.0, 1); try { FileOutputStream fos = new FileOutputStream("unimplseralizable.txt"); ObjectOutputStream oos = new ObjectOutputStream(fos); oos.writeObject(smallDog); oos.flush(); oos.close(); } catch (IOException e) { e.printStackTrace(); } }

結果輸出序列化後的檔案：

3、将以上序列化後的檔案進行反序列化

反序列化檔案seralizable.txt代碼片段

public void deserializeSmallDog(){ try { SmallDog smallDog = null; FileInputStream fis = new FileInputStream(new File("seralizable.txt")); ObjectInputStream ois = new ObjectInputStream(fis); smallDog = (SmallDog)ois.readObject(); System.out.println(smallDog.toString()); ois.close(); } catch (IOException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } }

輸出結果

SmallDog{name='小白', weight=4.0, age=1}

四、結論 要将對象進行序列化(将對象持久化或網絡傳輸)必須使對象實作 java.io.Serializable接口或者使用其他序列化庫，JDK自帶序列化并不是效率最高的。