Programming difference between POJO and Bean

问题:

I have the following two classes. Can I say the first one is a POJO class and the second one as a Bean class?

1) POJO class, since it has only getter and setter method, and all the member are declared as private

public class POJO {
    private int id;
    private String name;

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public void setId() {
        this.id = id;
    }

    public void setName() {
        this.name = name;
    }
}

2) Bean class - all the member variables are private, has getters and setters and implements Serializable interface

public class Bean implements java.io.Serializable {
    private String name;
    private Integer age;

    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return this.age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }
}

It also has a no-arg constructor.

回答1:

Only difference is bean can be serialized.

From Java docs - http://docs.oracle.com/javase/7/docs/api/java/io/Serializable.html

Serializability of a class is enabled by the class implementing the java.io.Serializable interface. Classes that do not implement this interface will not have any of their state serialized or deserialized. All subtypes of a serializable class are themselves serializable. The serialization interface has no methods or fields and serves only to identify the semantics of being serializable.

回答2:

the JavaBean class must implement either Serializable or Externalizable, must have a no-arg constructor,all JavaBean properties must public setter and getter methods (as appropriate) all JavaBean instance variables should be private