JPA 更新示例

JPA教程 - JPA更新示例

以下代碼顯示了如何通過僅使用映射實(shí)體的setter方法來更新實(shí)體。

下面的代碼在persist方法調(diào)用后用setter方法更新name字段。

從下一節(jié)中的數(shù)據(jù)庫轉(zhuǎn)儲(chǔ)我們可以看到，新的值被保存到數(shù)據(jù)庫。

    Professor emp = new Professor();

    emp.setId(1);
    emp.setName("name");
    em.persist(emp);
    
    emp.setName("New name");

例子

以下代碼來自Professor.java。

package cn.w3cschool.common;
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity 
@Table(name="EMP")
public class Professor  {
    @Id private int id;
    private String name;
    public int getId() {
        return id;
    }
    
    public void setId(int id) {
        this.id = id;
    }
    
    public String getName() {
        return name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    public String toString() {
        return "Professor id: " + getId() + " name: " + getName();
    }
}

下面的代碼來自PersonDaoImpl.java。

package cn.w3cschool.common;


import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import org.springframework.transaction.annotation.Transactional;

@Transactional
public class PersonDaoImpl {
  public void test(){
    
    Professor emp = new Professor();

    emp.setId(1);
    emp.setName("name");
    em.persist(emp);
    
    emp.setName("New name");
  }
  @PersistenceContext
  private EntityManager em;
}

以下是數(shù)據(jù)庫轉(zhuǎn)儲(chǔ)。

Table Name: EMP
 Row:
    Column Name: ID,
    Column Type: INTEGER:
    Column Value: 1

    Column Name: NAME,
    Column Type: VARCHAR:
    Column Value: New name