java关键字transient

1.在读java的源码时，遇到transient关键字声明变量。例如：

  // Generics and annotations support

    private transient String    signature;

    // generic info repository; lazily initialized

    private transient FieldRepository genericInfo;

在上面的代码中，不明白 signature和genericInfo声明有什么作用，而且用到了transient关键字修饰。

transient单词意思为瞬态，临时的意思。

对象序列化后读取对象时，瞬态属性不会被读取。

Fields declared as transient or static are ignored by the deserialization process.

对象实现序列化接口后反序列化时，不会创建新的对象，否则会创建。

示例代码:

package my.transientExceple.test;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Date;

//测试transient关键字有什么作用
public class LoggingInfo implements Serializable {
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	private Date loggingDate = new Date();   
    private String uid;   
    private transient String pwd;   
	
    LoggingInfo(String user,String password)
    {
    	uid=user;
    	pwd=password;
    }
    public String toString()
    {
    	String password=null;
    	if(pwd==null){
    		password="not set";
    	}else{
    		password=pwd;
    	}
    	return "logging info:\n"+"userId:"+uid+",\n loggingDate:+"+loggingDate.toString()+
    			"\n password:"+password;
    }
	
    
    public static void main(String args[]){
    	LoggingInfo logInfo = new LoggingInfo("MIKE", "xxxx");   
    	//System.out.println(logInfo.toString());   
    	 try {
    		 ObjectOutputStream o = new ObjectOutputStream(   
    	                new FileOutputStream("logInfo.out")); 
    	    	 o.writeObject(logInfo); 
			o.close();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}  
    	/* File file=new File("logInfo.out");
    	 System.out.println(file.getAbsoluteFile());
    	 F:\workspace\MyMvc\logInfo.out
    	 */
    	 try  
    	 {   
    	    @SuppressWarnings("resource")
			ObjectInputStream in =new ObjectInputStream(   
    	                 new FileInputStream("logInfo.out"));   
    	    LoggingInfo logInfo1 = (LoggingInfo)in.readObject();   
    	    System.out.println(logInfo1.toString());   
    	 }   
    	 catch(Exception e) {//deal with exception}   
    	 }
    }
	
}