JPA(Java Persistence API-java的持久化api)

• JPA是通过注解的方式来描述对象和表之间的映射关系

JPA使用

• 第一步在实体类中

    package com.risen.bean;
  
    import javax.persistence.*;
  
    /**
     * Author:
     * Date: 2019/12/19 14:43
     * Desc:
     */
    @Entity //声明持久化类
    @Table(name = "cst_customer") //映射类名和表名
    public class Customer {
        public String getCust_id() {
            return cust_id;
        }
  
        public void setCust_id(String cust_id) {
            this.cust_id = cust_id;
        }
  
        public String getCust_name() {
            return cust_name;
        }
  
        public void setCust_name(String cust_name) {
            this.cust_name = cust_name;
        }
  
        public String getCust_source() {
            return cust_source;
        }
  
        public void setCust_source(String cust_source) {
            this.cust_source = cust_source;
        }
  
        public String getCust_industry() {
            return cust_industry;
        }
  
        public void setCust_industry(String cust_industry) {
            this.cust_industry = cust_industry;
        }
  
        public String getCust_level() {
            return cust_level;
        }
  
        public void setCust_level(String cust_level) {
            this.cust_level = cust_level;
        }
  
        public String getCust_address() {
            return cust_address;
        }
  
        public void setCust_address(String cust_address) {
            this.cust_address = cust_address;
        }
  
        public String getCust_phone() {
            return cust_phone;
        }
  
        public void setCust_phone(String cust_phone) {
            this.cust_phone = cust_phone;
        }
  
        @Id //表示那个属性是oid属性
        @Column(name = "cust_id")  //oid属性和表的主键映射关系
        @GeneratedValue(strategy = GenerationType.IDENTITY)//声明主键的自增方式
        private String cust_id;// '客户编号(主键)'
  
        @Column(name = "cust_name") //其他属性和表中的字段映射关系(如果属性和字段值名称一样可以省略不写)
          private String cust_name ;// '客户名称(公司名称)'
        @Column(name = "cust_source")
          private String cust_source ;//'客户信息来源'
        @Column(name = "cust_industry")
          private String cust_industry ;// '客户所属行业'
        @Column(name = "cust_level")
          private String cust_level ;// '客户级别'
        @Column(name = "cust_address")
          private String cust_address ;// '客户联系地址'
        @Column(name = "cust_phone")
          private String cust_phone ;// '客户联系电话'
    }
• 第二步需要在src目录下创建为META-INF的目录,并且在META-INF目录下需要创建persistence.xml

  <?xml version="1.0" encoding="utf-8" ?>
  <persistence xmlns="http://java.sun.com/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
             http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd" version="2.0">
    <!--至少得有一個持久化單元(至少得有一个数据库的连接信息，多个数据库连接信息复制多个persistence-unit标签即可)-->
    <persistence-unit name="MySQL" transaction-type="RESOURCE_LOCAL">
        <properties>
            <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" />
            <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/web_demo?verifyServerCertificate=false&amp;useSSL=false&amp;characterEncoding=UTF8" />
            <property name="hibernate.connection.username" value="root" />
            <property name="hibernate.connection.password" value="123456" />
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect" />
            <property name="hibernate.connection.provider_class" value="org.hibernate.c3p0.internal.C3P0ConnectionProvider" />
            <property name="hibernate.show_sql" value="true" />
            <property name="hibernate.format_sql" value="true" />
            <property name="hibernate.hbm2ddl.auto" value="update" />
        </properties>
    </persistence-unit>
  </persistence>

第三步写个demo测试一下