java - 热衷于使用 JPQL 更新某些记录？

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我有这个代码:

public void uploadSaveGame(User user, String saveData)
{
    EntityTransaction entr=em.getTransaction();
        entr.begin();
    TypedQuery<Save> query = em.createQuery("UPDATE WithSave2 SET savedata WHERE u.login = :user", Save.class);              
    query.setParameter("login", user);
    query.setParameter("save", saveData);
    em.getTransaction().commit();
}

我正在尝试更新列 saveData。这是我的类(class) WitSave2:

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package com.dke.ps.Tables;

import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.xml.bind.annotation.XmlRootElement;

/**
 *
 * @author michal
 */
@Entity
@Table(name = "with_save2")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "WithSave2.findAll", query = "SELECT w FROM WithSave2 w")
    , @NamedQuery(name = "WithSave2.findBySaveid", query = "SELECT w FROM WithSave2 w WHERE w.saveid = :saveid")
    , @NamedQuery(name = "WithSave2.findByLogin", query = "SELECT w FROM WithSave2 w WHERE w.login = :login")
    , @NamedQuery(name = "WithSave2.findBySavedata", query = "SELECT w FROM WithSave2 w WHERE w.savedata = :savedata")})
public class WithSave2 implements Serializable {

    private static final long serialVersionUID = 1L;
    @Column(name = "saveid")
    @Id
    private Integer saveid;
    @Column(name = "login")
    private String login;
    @Column(name = "savedata")
    private String savedata;

    public WithSave2() {
    }

    public Integer getSaveid() {
        return saveid;
    }

    public void setSaveid(Integer saveid) {
        this.saveid = saveid;
    }

    public String getLogin() {
        return login;
    }

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

    public String getSavedata() {
        return savedata;
    }

    public void setSavedata(String savedata) {
        this.savedata = savedata;
    }

}

更新列的查询是否正确？我不太确定，尤其是这一行:

query.setParameter("login", user);
        query.setParameter("save", saveData); 

有人可以帮助我吗？非常感谢:)

Answer 1

给你几件事:

• 您必须为要更改的列分配一个新值(否则不是更新的语句)
• 您必须运行查询..而不仅仅是定义它
• 当您使用手动事务时，最好添加一些异常管理以防万一。

• 执行批量更新时不需要 TypedQuery。

  EntityTransaction entr=em.getTransaction();
  entr.begin();
  
  try{
    Query query = em.createQuery("UPDATE WithSave2 
      SET savedata = :saveData WHERE u.login = :user", Save.class);              
    query.setParameter("login", user);
    query.setParameter("save", saveData);
  
    query.executeUpdate(); 
  
    entr.commit();
  }catch(Exception e){
    entr.rollback();
  }