SpringDataJPA的初步学习与使用

最新推荐文章于 2025-10-13 17:57:21 发布

原创最新推荐文章于 2025-10-13 17:57:21 发布 · 205 阅读

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文章标签：

#学习 #hibernate #java #spring

本文介绍了如何在Spring Boot项目中利用Spring Data JPA进行数据库依赖管理，配置数据库连接，创建实体类及DAO，并展示了基本的CRUD操作实例。通过Knowledge实体和KnowledgeDao接口，读者将学习到如何执行查询、更新和删除操作。

一、引入依赖

<!--Spring Data JPA依赖-->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<!--数据库驱动，这里使用sqlServer-->
<dependency>
    <groupId>com.microsoft.sqlserver</groupId>
    <artifactId>sqljdbc4</artifactId>
    <version>4.0</version>
</dependency>

二、配置文件

spring:
    datasource:
        url: ""
        username: ""
        password: ""
        driver-class-name: ""
    jpa:
        hibernate:
            ddl-auto: update
        show-sql: true

三、使用

实体类

package com.example.jpademo.entity;

import java.io.Serializable;
import java.util.Date;
import javax.persistence.*;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.hibernate.annotations.Proxy;

/**
 * knowledge
 * @author 
 */
@Table(name="knowledge")
@Data
@Entity
@NoArgsConstructor
@AllArgsConstructor
public class Knowledge implements Serializable {
    /**
     * 条目编号
     */
    @Id
    @GeneratedValue(generator = "JDBC",strategy = GenerationType.IDENTITY)
    private Integer id;

    /**
     * 标题
     */
    private String title;

    /**
     * 最后更改时间
     */
    private Date lastmodified;

    /**
     * 内容
     */
    private String content;

    /**
     * 类别编号
     */
    private Integer classid;

    private static final long serialVersionUID = 1L;


    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append(getClass().getSimpleName());
        sb.append(" [");
        sb.append("Hash = ").append(hashCode());
        sb.append(", id=").append(id);
        sb.append(", title=").append(title);
        sb.append(", lastmodified=").append(lastmodified);
        sb.append(", content=").append(content);
        sb.append(", classid=").append(classid);
        sb.append(", serialVersionUID=").append(serialVersionUID);
        sb.append("]");
        return sb.toString();
    }
}

DAO

package com.example.jpademo.dao;

import com.example.jpademo.entity.Knowledge;
import org.springframework.data.domain.Page;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Modifying;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import org.springframework.transaction.annotation.Transactional;

import javax.persistence.Column;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
import java.util.List;

public interface KnowledgeDao extends JpaRepository<Knowledge,Integer>,JpaSpecificationExecutor<Knowledge>{
    //id>= min AND id<=max
    List<Knowledge> findByIdGreaterThanAndIdLessThan(Integer min, Integer max);

    //id>= min AND id<=max
    List<Knowledge> findByIdBetween(Integer min,Integer max);

    //id==id
    Knowledge findByIdIs(Integer id);

    //id==id
    Knowledge findByIdEquals(Integer id);

    //And Or Between(a>=? AND ?<=? )

    //GreaterThan(>=)  LessThan(<=)

    //判断空值 IsNull IsNotNull NotNull

    //模糊查询 Like NotLike

    //Is Not Equals

    //OrderBy

    //In NotIn

    //TRUE FALSE

    /*
     * 时间日期 After  Before
     * findByStartDateAfter
     * where x.startDate > ?1（After）
     * */

    //StartingWith EndingWith Containing

    //IgnoreCase

    //top

    /*
    * 注解
    * @Query
    * @Param
    * */
    @Query("from Knowledge where content like %:content%")
    List<Knowledge> findKnowledgeByContent(@Param("content") String content);

    @Query(value = "select * from knowledge where content like %:content%",nativeQuery =true)
    List<Knowledge> findKnowledgeByTitle(@Param("content") String content);

    @Modifying //修改查询，标记为更新
    @Transactional
    @Query("update Knowledge set content =:content where id =:id")
    int updateKnowledge(@Param("content") String content,@Param("id") int id);
}

使用

package com.example.jpademo;

import com.example.jpademo.dao.KnowledgeDao;
import com.example.jpademo.entity.Knowledge;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.repository.JpaRepository;

import javax.annotation.Resource;
import java.util.List;
import java.util.Optional;

@SpringBootTest
class JpaDemoApplicationTests {

    @Resource
    KnowledgeDao knowledgeDao;

    @Test
    void contextLoads() {
        Knowledge knowledge=new Knowledge();
        //根据ID返回单个实体
        System.out.println("根据ID返回单个实体-->"+knowledgeDao.findById(97));
        //根据ID返回实体是否存在
        System.out.println("返回实体是否存在-->"+knowledgeDao.existsById(97));
        //返回实体总数
        System.out.println("实体总数-->"+knowledgeDao.count());
        //分页返回实体
        Sort sort = Sort.by(Sort.Order.desc("lastmodified"));
        System.out.println("第一页数据");
        Pageable pageable = PageRequest.of(0, 2,sort);
        knowledgeDao.findAll(pageable).forEach(System.out::println);

        //使用方法命名查询
        knowledgeDao.findByIdGreaterThanAndIdLessThan(94,100).forEach(System.out::println);
        knowledgeDao.findByIdBetween(95,97).forEach(System.out::println);
        //增删改

        //修改
        //获取实体
        knowledge=knowledgeDao.findById(97).get();
        knowledge.setTitle("SQL不太难");
        knowledge.setId(null);
        //根据id判断添加或修改
        Knowledge save = knowledgeDao.save(knowledge);
        System.out.println(save);
        //删除
        knowledgeDao.delete(knowledge);

        knowledgeDao.findKnowledgeByContent("Java").forEach(System.out::println);

        knowledgeDao.findKnowledgeByTitle("Java").forEach(System.out::println);

        System.out.println(knowledgeDao.updateKnowledge("第二次更新的测试内容", 97));
    }
}