Question

我学习了hibernate框架，我对生成的sql很困惑。我有以下代码：

表：

CREATE TABLE users (
 user_id int NOT NULL AUTO_INCREMENT,
 login varchar(20) UNIQUE,
 pass varchar(20),
 user_name varchar(20),
 surname varchar(20),
 PRIMARY KEY (user_id)
)

型号：

@Entity
 @Table(name="users", catalog="maximodb")
 public class User implements Serializable{

@Id
@Column(name="user_id")
@GeneratedValue(strategy =GenerationType.IDENTITY)
private Integer userId;

@Column(name = "login", unique = true, length = 20)
private String login;

@Column(name = "pass", length = 20)
private String pass;

@Column(name = "user_name", length = 20)
private String userName;

@Column(name = "surname", length = 20)
private String surname;


@ManyToMany(fetch = FetchType.LAZY)
@JoinTable(name = "users_roles", joinColumns = { @JoinColumn(name = "user_id") }, inverseJoinColumns = { @JoinColumn(name = "role_id") })
private Set<Role> userRoles = new HashSet<Role>();

public User() {
}

public User(String login, String pass, String userName, String surname) {
    this.login = login;
    this.pass = pass;
    this.userName = userName;
    this.surname = surname;
}


public Integer getUserId() {
    return this.userId;
}

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

public String getLogin() {
    return this.login;
}

public void setLogin(String login) {
    this.login = login;
}

public String getPass() {
    return this.pass;
}

public void setPass(String pass) {
    this.pass = pass;
}

public String getUserName() {
    return this.userName;
}

public void setUserName(String userName) {
    this.userName = userName;
}

public String getSurname() {
    return this.surname;
}

public void setSurname(String surname) {
    this.surname = surname;
}

public Set<Role> getUserRoles() {
    return userRoles;
}

public void setUserRoles(Set<Role> userRoles) {
    this.userRoles = userRoles;
}

@Override
public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + ((login == null) ? 0 : login.hashCode());
    result = prime * result + ((pass == null) ? 0 : pass.hashCode());
    result = prime * result + ((surname == null) ? 0 : surname.hashCode());
    result = prime * result + ((userId == null) ? 0 : userId.hashCode());
    result = prime * result + ((userName == null) ? 0 : userName.hashCode());
    result = prime * result + ((userRoles == null) ? 0 : userRoles.hashCode());
    return result;
}

@Override
public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (obj == null)
        return false;
    if (getClass() != obj.getClass())
        return false;
    User other = (User) obj;
    if (login == null) {
        if (other.login != null)
            return false;
    } else if (!login.equals(other.login))
        return false;
    if (pass == null) {
        if (other.pass != null)
            return false;
    } else if (!pass.equals(other.pass))
        return false;
    if (surname == null) {
        if (other.surname != null)
            return false;
    } else if (!surname.equals(other.surname))
        return false;
    if (userId == null) {
        if (other.userId != null)
            return false;
    } else if (!userId.equals(other.userId))
        return false;
    if (userName == null) {
        if (other.userName != null)
            return false;
    } else if (!userName.equals(other.userName))
        return false;
    if (userRoles == null) {
        if (other.userRoles != null)
            return false;
    } else if (!userRoles.equals(other.userRoles))
        return false;
    return true;
}

}

现在...... dao功能（两个变种）：

第一个：

List<User> users = new ArrayList<User>();

    users = sessionFactory.getCurrentSession()
        .createQuery("from User where login= :login")
        .setString( "login", login )
        .list();

    if (users.size() > 0) {
        return users.get(0);
    } else {
        return null;
    }

返回sql：

select
    user0_.user_id as user_id1_1_,
    user0_.login as login2_1_,
    user0_.pass as pass3_1_,
    user0_.surname as surname4_1_,
    user0_.user_name as user_nam5_1_ 
from
    maximodb.users user0_ 
where
    user0_.login=?

第二个变种：

    Criteria criteria =  sessionFactory.getCurrentSession().createCriteria(User.class);
    List<User> a = (List<User>) criteria.list();

User us = a.get(0);


    return us;

返回sql：

select
    this_.user_id as user_id1_1_0_,
    this_.login as login2_1_0_,
    this_.pass as pass3_1_0_,
    this_.surname as surname4_1_0_,
    this_.user_name as user_nam5_1_0_ 
from
    maximodb.users this_

第二个变体是非常正确的，并从db获取用户。但在第一种情况下，有一个空指针异常而不是User对象。什么是不正确的？值得一提的是，生成的sql在MySql Workbench中运行良好（第一种情况）。

Answer 1

第一个变体尝试获取具有给定登录名但未找到此登录用户的用户（验证在数据库中是否存在具有给定登录名的用户）。
第二个变量列出数据库中的所有用户，而不是第一个。您的用户表包含一些用户，这就是此变体返回用户而不是null的原因。

Hibernate HQL / DAO功能不正确/编码Spring Security时 - 注释

1 个答案: