Java Java.io.ObjectInputStream.getField.get() 方法

描述

java.io.ObjectInputStream.getField.get(String name, Object val)方法从持久性字段获取命名的Object字段的值。

声明

以下是java.io.ObjectInputStream.getField.get()方法的声明。

 public abstract Object get(String name, Object val)

参数

name字段名称。
val如果name没有值，则使用默认值。

返回值

此方法返回命名的Object字段的值。

异常

IOException如果从基础InputStream读取时发生I / O错误。
IllegalArgumentException如果名称的类型不可序列化或字段类型不正确。

例子

以下示例显示java.io.ObjectInputStream.getField.get()方法的用法。

 
package com.jc2182;
import java.io.*;

public class ObjectInputStreamDemo implements Serializable {
   public static void main(String[] args) {
      try {
         // create a new file with an ObjectOutputStream
         FileOutputStream out = new FileOutputStream("test.txt");
         ObjectOutputStream oout = new ObjectOutputStream(out);

         // write something in the file
         oout.writeObject(new Example());
         oout.flush();
         oout.close();

         // create an ObjectInputStream for the file we created before
         ObjectInputStream ois = new ObjectInputStream(new FileInputStream("test.txt"));

         // read an object from the stream and cast it to Example
         Example a = (Example) ois.readObject();

         // print var of a
         System.out.println("" + a.var);

      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }

   static public class Example implements Serializable {
      static Object var = "Hello World";
      
      // assign a new serialPersistentFields 
      private static final ObjectStreamField[] serialPersistentFields = {
         new ObjectStreamField("var", Object.class)
      };

      private void readObject(ObjectInputStream in)
         throws IOException, ClassNotFoundException {

         // get the field and assign it at var
         ObjectInputStream.GetField fields = in.readFields();

         // get var
         var = fields.get("var", null);
      }

      private void writeObject(ObjectOutputStream out) throws IOException {

         // write into the ObjectStreamField array the variable string
         ObjectOutputStream.PutField fields = out.putFields();
         fields.put("var", var);
         out.writeFields();
      }
   }
}

让我们编译并运行以上程序，这将产生以下结果-

 Hello World