第6章 Spring Boot的数据访问 一、Spring Data JPA(4、@Query和@Modifying注解)

学习目标:

一、Spring Data JPA
4、@Query和@Modifying注解


学习内容:

在上两节中的查询方法必须严格按照Spring Data JPA的查询关键字命名规范进行查询方法命名。如何摆脱查询关键字和关联查询命名规范约束呢?可以通过@Query、@NamedQuery直接定义JPQL语句进行数据的访问操作。

1.@Query注解

使用@Query注解可以将JPQL语句直接定义在数据访问接口方法上,并且接口方法名不受查询关键字和关联查询命名规范约束。示例代码如下:

public interface AuthorityRepository extends JpaRepository<Authority, Integer>{
	/**
	 * 根据用户名查询用户所拥有的权限(关联查询)
	 */
	@Query("select a from Authority a inner join a.userList u where u.username = ?1")
	public List<Authority> findByUserListUsername(String username);
}

使用@Query注解定义JPQL语句,可以直接返回List>对象。示例代码如下:

/**
* 根据作者id查询文章信息(标题和内容)
*/
@Query("select new Map(a.title as title, a.content as content) from Article a where a.author.id = ?1 ")
public List<Map<String, Object>> findTitleAndContentByAuthorId(Integer id);

使用@Query注解定义JPQL语句,之前的方法是使用参数位置(“?1指代的是获取方法形参列表中的第一个参数值,1代表的是参数位置,以此类推)来获取参数值。除此之外,Spring Data JPA还支持使用名称来获取参数值,使用格式为“:参数名称”。示例代码如下:

@Query("select a from Article a where a.author.aname = :aname1 and a.author.aname.id = :id1 ")
public List<Article> findArticleByAuthorAnameAndId(@Param("aname1") String aname, @Param("id1") Integer id);

2.@Modifying注解

可以使用@Modifying和@Query注解组合定义在数据访问接口方法上,进行更新查询操作。示例代码如下:

     /**
	 * 根据作者id删除作者
	 */
	@Modifying
	@Query("delete from Author a where a.id = ?1")
	public int deleteAuthorByAuthorId(int id);

【例6-5】@Query和@Modifying注解的使用方法。

首先,为【例6-5】创建基于Spring Data JPA的Spring Boot Web应用ch6_3。ch6_3应用的数据库、pom.xml以及application.properties与ch6_2应用基本一样,不再赘述。
第6章 Spring Boot的数据访问 一、Spring Data JPA(4、@Query和@Modifying注解)_第1张图片

1)创建持久化实体类

创建名为com.ch.ch6_3.entity的包,并在该包中创建名为Author和Article的持久化实体类。
Author的具体代码如下:

package com.ch.ch6_3.entity;
import java.io.Serializable;
import java.util.List;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
@Entity
@Table(name = "author_table")
@JsonIgnoreProperties(value = { "hibernateLazyInitializer"})
public class Author implements Serializable{
	private static final long serialVersionUID = 1L;
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private int id;
	//作者名
	private String aname;
	//文章列表,作者与文章是一对多的关系
    @OneToMany(
    		mappedBy = "author",
    		cascade=CascadeType.ALL,
    		targetEntity = Article.class, 
    		fetch=FetchType.LAZY
    		)
    private List<Article> articleList;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getAname() {
		return aname;
	}
	public void setAname(String aname) {
		this.aname = aname;
	}
	public List<Article> getArticleList() {
		return articleList;
	}
	public void setArticleList(List<Article> articleList) {
		this.articleList = articleList;
	}
}

Article的具体代码如下:

package com.ch.ch6_3.entity;
import java.io.Serializable;
import javax.persistence.Basic;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.Lob;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
import javax.validation.constraints.NotEmpty;
import javax.validation.constraints.Size;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
@Entity
@Table(name = "article_table")
@JsonIgnoreProperties(value = { "hibernateLazyInitializer"})
public class Article  implements Serializable{
	private static final long serialVersionUID = 1L;
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private int id;
	//标题
	@NotEmpty(message = "标题不能为空")
    @Size(min = 2, max = 50)
    @Column(nullable = false, length = 50) 
    private String title;
	//文章内容
    @Lob  //大对象,映射 为MySQL的Long文本类型
    @Basic(fetch = FetchType.LAZY) 
    @NotEmpty(message = "内容不能为空")
    @Size(min = 2)
    @Column(nullable = false) 
    private String content;
    //所属作者,文章与作者是多对一的关系
    @ManyToOne(cascade={CascadeType.MERGE,CascadeType.REFRESH},optional=false)
    //可选属性optional=false,表示author不能为空。删除文章,不影响用户
    @JoinColumn(name="id_author_id")//设置在article表中的关联字段(外键)
    @JsonIgnore
    private Author author;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getTitle() {
		return title;
	}
	public void setTitle(String title) {
		this.title = title;
	}
	public String getContent() {
		return content;
	}
	public void setContent(String content) {
		this.content = content;
	}
	public Author getAuthor() {
		return author;
	}
	public void setAuthor(Author author) {
		this.author = author;
	}
}

2)创建数据访问层

在com.ch.ch6_3.repository包中,创建名为AuthorRepository和ArticleRepository的接口。

AuthorRepository的代码如下:

package com.ch.ch6_3.repository;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Modifying;
import org.springframework.data.jpa.repository.Query;
import com.ch.ch6_3.entity.Author;
public interface AuthorRepository extends JpaRepository<Author, Integer>{
	/**
	 * 根据文章标题包含的内容,查询作者(关联查询)
	 */
	@Query("select a from Author a  inner join  a.articleList t where t.title like %?1%" )
	public Author findAuthorByArticleListtitleContaining(String title);
	/**
	 * 根据作者id删除作者
	 */
	@Modifying
	@Query("delete from Author a where a.id = ?1")
	public int deleteAuthorByAuthorId(int id);
}

ArticleRepository的代码如下:

package com.ch.ch6_3.repository;
import java.util.List;
import java.util.Map;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import com.ch.ch6_3.entity.Article;
public interface ArticleRepository extends JpaRepository<Article, Integer>{
	/**
	 * 根据作者id查询文章信息(标题和内容)
	 */
	@Query("select new Map(a.title as title, a.content as content) from Article a where a.author.id = ?1 ")
	public List<Map<String, Object>> findTitleAndContentByAuthorId(Integer id);
	/**
	 * 根据作者名和作者id查询文章信息
	 */
	@Query("select a from Article a where a.author.aname = :aname1 and a.author.id = :id1 ")
	public List<Article> findArticleByAuthorAnameAndId(@Param("aname1") String aname, @Param("id1") Integer id);
	
}

3)创建业务层

在com.ch.ch6_3.service包中,创建名为AuthorAndArticleService的接口和接口实现类AuthorAndArticleServiceImpl。

AuthorAndArticleService的代码如下:

package com.ch.ch6_3.service;
import java.util.List;
import java.util.Map;
import com.ch.ch6_3.entity.Article;
import com.ch.ch6_3.entity.Author;
public interface AuthorAndArticleService {
	public List<Map<String, Object>> findTitleAndContentByAuthorId(Integer id);
	public List<Article> findArticleByAuthorAnameAndId(String aname, Integer id);
	public Author findAuthorByArticleListtitleContaining(String title);
	public int deleteAuthorByAuthorId(int id);
}

AuthorAndArticleServiceImpl的代码如下:

package com.ch.ch6_3.service;
import java.util.List;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import com.ch.ch6_3.entity.Article;
import com.ch.ch6_3.entity.Author;
import com.ch.ch6_3.repository.ArticleRepository;
import com.ch.ch6_3.repository.AuthorRepository;
@Service
@Transactional
public class AuthorAndArticleServiceImpl implements AuthorAndArticleService{
	@Autowired
	private AuthorRepository authorRepository;
	@Autowired
	private ArticleRepository articleRepository;
	@Override
	public List<Map<String, Object>> findTitleAndContentByAuthorId(Integer id) {
		return articleRepository.findTitleAndContentByAuthorId(id);
	}
	@Override
	public List<Article> findArticleByAuthorAnameAndId(String aname, Integer id) {
		return articleRepository.findArticleByAuthorAnameAndId(aname, id);
	}
	@Override
	public Author findAuthorByArticleListtitleContaining(String title) {
		return authorRepository.findAuthorByArticleListtitleContaining(title);
	}
	@Override
	public int deleteAuthorByAuthorId(int id) {
		return authorRepository.deleteAuthorByAuthorId(id);
	}
}

4)创建控制器类
在com.ch.ch6_3.controller包中,创建名为TestOneToManyController的控制器类。

TestOneToManyController的代码如下:

package com.ch.ch6_3.controller;
import java.util.List;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.ch.ch6_3.entity.Article;
import com.ch.ch6_3.entity.Author;
import com.ch.ch6_3.service.AuthorAndArticleService;
@RestController
public class TestOneToManyController {
	@Autowired 
	private AuthorAndArticleService authorAndArticleService;
	@RequestMapping("/findTitleAndContentByAuthorId")
	public List<Map<String, Object>> findTitleAndContentByAuthorId(Integer id){
		return authorAndArticleService.findTitleAndContentByAuthorId(id);
	}
	@RequestMapping("/findArticleByAuthorAnameAndId")
	public List<Article> findArticleByAuthorAnameAndId(String aname, Integer id){
		return authorAndArticleService.findArticleByAuthorAnameAndId(aname, id);
	}
	@RequestMapping("/findAuthorByArticleListtitleContaining")
	public Author findAuthorByArticleListtitleContaining(String title) {
		return authorAndArticleService.findAuthorByArticleListtitleContaining(title);
	}
	@RequestMapping("/deleteAuthorByAuthorId")
	public int deleteAuthorByAuthorId(int id) {
		return authorAndArticleService.deleteAuthorByAuthorId(id);
	}
}

5)运行

查询作者id=1的文章标题和内容:

第6章 Spring Boot的数据访问 一、Spring Data JPA(4、@Query和@Modifying注解)_第2张图片


学习时间:

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学习产出:

1、 技术笔记 1 遍
2、CSDN 技术博客 1 篇

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