将数据另存为实体的默认构造函数时，出现休眠异常？ 我在哪里做错了

Question

Database tables:

1. CREATE TABLE user ( uid serial NOT NULL, user_id character varying(10) NOT NULL, password character varying(50), screen_name character varying(100) NOT NULL, auth_type integer NOT NULL, active_flag boolean NOT NULL, delete_flag boolean NOT NULL, created_by integer NOT NULL, created_on timestamp with time zone NOT NULL, modified_by integer NOT NULL, modified_on timestamp with time zone NOT NULL, CONSTRAINT user_pkey PRIMARY KEY (uid ), CONSTRAINT user_user_id_key UNIQUE (user_id ) )

2. CREATE TABLE PREFERENCES ( UID serial NOT NULL, USER_ID integer NOT NULL, Theme character varying(50), Template character varying(50), CREATED_BY integer NOT NULL, CREATED_ON timestamp with time zone NOT NULL, MODIFIED_BY integer NOT NULL, MODIFIED_ON timestamp with time zone NOT NULL, CONSTRAINT PREFERENCES_PKEY PRIMARY KEY (USER_ID), CONSTRAINT PREFERENCES_FKEY FOREIGN KEY (USER_ID) REFERENCES USER (UID) MATCH SIMPLE ON UPDATE NO ACTION ON DELETE NO ACTION

);

I our application we are using JPA annotations

hibernate mapping using annotations

Due to security reason i cant able to upload entire file

user.java file is like this

I have defined properties along with the property for preferences

private UserPreferences userPreferences;

I am doing mapping as

line 1: @OneToOne(fetch = FetchType.EAGER,cascade = CascadeType.ALL)
line2: @JoinColumn(name="UID",referencedColumnName="USER_ID")

preferences.java file

This is my userpreference file

@Entity
@Table(name="USER_PREFERENCES")
public class UserPreferences {
    private int uid;
     private String userId;
     private String theme;
     private String template;

    public UserPreferences(int uid, String userId, String theme, String template, RecordDetails recordDetails) {
        super();
        this.uid = uid;
        this.userId = userId;
        this.theme = theme;
        this.template = template;

    }


    @Id
    @Column(name="UID",updatable=false)
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public int getUid() {
        return uid;
    }

    public void setUid(int uid) {
        this.uid = uid;
    }


    @Column(name="USER_ID", updatable=false, unique=true)
    public String getUserId() {
        return userId;
    }


    public void setUserId(String userId) {
        this.userId = userId;
    }


    @Column(name="THEME")
    public String getTheme() {
        return theme;
    }


    public void setTheme(String theme) {
        this.theme = theme;
    }

    @Column(name="TEMPLATE")
    public String getTemplate() {
        return template;
    }

    public void setTemplate(String template) {
        this.template = template;
    }

}

all the properties as per the database table i have given in it.

I am having users list and i want to assign a preference for each user so i took one to one mapping

When there is no row for a preference table i can able to see the list of users and add the preference for any user. once after coming back and getting the userlist i am seeing an error as

No default constructor for entity: UserPreferences

Can you please help me why i am getting this only after adding a row in preference how can i solve it.

Here at the below line i am getting an exception

Criteria criteria = session.createCriteria(User.class); usersList = criteria.setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY).list();

Thanks in advance

Answer 1

Since you defined an argument-constructor, you need to explictly define the default constructor.

Just add

public UserPreferences() {
    // needed for JPA
}

to your class.

Hibernate uses Reflection to instantiate the entity-classes. Reflection uses Class<T>.newInstance() to do so.