Use the keyword transient

Outline

In Java, a class can implement the Serializable interface objects of this class can be serialized, this sequence mode provides a lot of convenience for developers, we do not have to care about the specific sequence of the process, as long as the class implements Serializable interfaces, all the properties of this class are automatically serialized. But sometimes we need to let some of the properties of the class are not serialized, such as password information, for security reasons, do not want to be transmitted or persistence in the network to the local operation. As long precede the corresponding attribute transient keywords, you can achieve some of the properties are not serialized, the life cycle of the property exists only in the memory of the caller will not be written to disk persistence.

The use of transient

public class TransientTest {

    public static void main(String[] args) { User user = new User(); user.setUsername("Github"); user.setPassword("123456"); System.out.println("read before Serializable: "); System.out.println("username: " + user.getUsername()); System.err.println("password: " + user.getPassword()); try { ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream("user.txt")); os.writeObject(user); // 将User对象写进文件  os.flush(); os.close(); } catch (IOException e) { e.printStackTrace(); } try { ObjectInputStream is = new ObjectInputStream(new FileInputStream("user.txt")); user = (User) is.readObject(); // 从流中读取User的数据  is.close(); System.out.println("\nread after Serializable: "); System.out.println("username: " + user.getUsername()); System.err.println("password: " + user.getPassword()); } catch (IOException | ClassNotFoundException e) { e.printStackTrace(); } } } public class User implements Serializable { private static final long serialVersionUID = 1234567890L; private String username; private transient String password; public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } }

Operating results :

 

 

transient modification of static variables

public class TransientTest {

    public static void main(String[] args) { User user = new User(); user.setUsername("Github"); user.setPassword("123456"); System.out.println("read before Serializable: "); System.out.println("username: " + user.getUsername()); System.err.println("password: " + user.getPassword()); try { ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream("user.txt")); os.writeObject(user); // 将User对象写进文件  os.flush(); os.close(); } catch (IOException e) { e.printStackTrace(); } try { // 在反序列化前盖板username的值  user.setUsername("Tom"); ObjectInputStream is = new ObjectInputStream(new FileInputStream("user.txt")); user = (User) is.readObject(); // 从流中读取User的数据  is.close(); System.out.println("\nread after Serializable: "); System.out.println("username: " + user.getUsername()); System.err.println("password: " + user.getPassword()); } catch (IOException | ClassNotFoundException e) { e.printStackTrace(); } } } public class User implements Serializable { private static final long serialVersionUID = 1234567890L; private static String username; private transient String password; public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } }

Operating results :

 

 

to sum up

1. Once the variables are modified transient, variable object persistence will no longer be part of the variable content after serialization can not gain access.
2. transient keyword can only modify variables, methods and classes can not be modified. Local variables can not be modified transient keyword. If the variable is a user-defined class variables, the class needs to implement Serializable interface.
3. A static variable regardless of whether the modification is transient, not be serialized.