嗯,这个问题几乎说明了一切.使用JPARepository,我如何更新实体?
JPARepository只有一个save方法,它没有告诉我它实际上是在创建还是在更新.例如,我向数据库用户插入一个简单的对象,它有三个字段:firstname
、lastname
和age
:
@Entity
public class User {
private String firstname;
private String lastname;
//Setters and getters for age omitted, but they are the same as with firstname and lastname.
private int age;
@Column
public String getFirstname() {
return firstname;
}
public void setFirstname(String firstname) {
this.firstname = firstname;
}
@Column
public String getLastname() {
return lastname;
}
public void setLastname(String lastname) {
this.lastname = lastname;
}
private long userId;
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
public long getUserId(){
return this.userId;
}
public void setUserId(long userId){
this.userId = userId;
}
}
然后我简单地调用save()
,这实际上是对数据库的插入:
User user1 = new User();
user1.setFirstname("john"); user1.setLastname("dew");
user1.setAge(16);
userService.saveUser(user1);// This call is actually using the JPARepository: userRepository.save(user);
到现在为止,一直都还不错.现在我想更新这个用户,比如改变他的年龄.为此,我可以使用QueryDSL或NamedQuery之类的查询.但是,考虑到我只想使用spring数据jpa和JPARepository,我该如何告诉它,我想进行更新,而不是插入?
具体来说,我如何告诉spring data jpa,具有相同用户名和名字的用户实际上是平等的,并且应该更新现有实体?压倒平等并不能解决这个问题.