jpa建立视图与实体的映射

比眉伴天荒 2022-01-21 03:27 560阅读 0赞

其实和实际table 与实体建立映射方式一样

# 视图 user\_view #

比如：  
我有以下视图：user\_view  
![在这里插入图片描述][20190607223547987.png]由于其中几个数据是由其他表统计而来，为了减小代码编写难度，采用视图的方式

# 实体 UserInfoView #

视图对应的实体UserInfoView.java  
**注意：如果表名与实体不一致，在映射时需要指定name 属性**

@Table(name = "user_view")
    @Entity
    
    public class UserInfoView { 
        @Id
        private Integer id;
        @Column
        private String account;
        @Column
        private String nikeName;
        @Column
        private String photo;
        @Column
        private String about;
        @Column
        private String signature;
        @Column
        private Integer likeCount;
        @Column
        private Integer articleCount;
        @Column
        private Integer visitCount;
        @Column
        private Integer fansCount;
    
        public Integer getId() { 
            return id;
        }
    
        public void setId(Integer id) { 
            this.id = id;
        }
    
        public String getAccount() { 
            return account;
        }
    
        public void setAccount(String account) { 
            this.account = account;
        }
    
        public String getNikeName() { 
            return nikeName;
        }
    
        public void setNikeName(String nikeName) { 
            this.nikeName = nikeName;
        }
    
        public String getPhoto() { 
            return photo;
        }
    
        public void setPhoto(String photo) { 
            this.photo = photo;
        }
    
        public String getAbout() { 
            return about;
        }
    
        public void setAbout(String about) { 
            this.about = about;
        }
    
        public String getSignature() { 
            return signature;
        }
    
        public void setSignature(String signature) { 
            this.signature = signature;
        }
    
        public Integer getLikeCount() { 
            return likeCount;
        }
    
        public void setLikeCount(Integer likeCount) { 
            this.likeCount = likeCount;
        }
    
        public Integer getArticleCount() { 
            return articleCount;
        }
    
        public void setArticleCount(Integer articleCount) { 
            this.articleCount = articleCount;
        }
    
        public Integer getVisitCount() { 
            return visitCount;
        }
    
        public void setVisitCount(Integer visitCount) { 
            this.visitCount = visitCount;
        }
    
        public Integer getFansCount() { 
            return fansCount;
        }
    
        public void setFansCount(Integer fansCount) { 
            this.fansCount = fansCount;
        }
    }

# dao 定义： #

public interface UserInfoViewDao extends CrudRepository<UserInfoView, Integer> { 
        UserInfoView findByAccount(String account);
    
    }

# 测试： #

@RunWith(SpringRunner.class)
    @SpringBootTest
    @Slf4j
    public class BlogApplicationTests { 
        @Autowired
        UserInfoViewDao userInfoViewDao;
    
         @Test
        public void testViewDao(){ 
            log.info("view:{}",userInfoViewDao.findByAccount("zhangsan"));
         }
    }

# 效果; #

Hibernate: select userinfovi0_.id as id1_12_, userinfovi0_.about as about2_12_, userinfovi0_.account as account3_12_, userinfovi0_.article_count as article_4_12_, userinfovi0_.fans_count as fans_cou5_12_, userinfovi0_.like_count as like_cou6_12_, userinfovi0_.nike_name as nike_nam7_12_, userinfovi0_.photo as photo8_12_, userinfovi0_.signature as signatur9_12_, userinfovi0_.visit_count as visit_c10_12_ from user_view userinfovi0_ where userinfovi0_.account=?
    2019-06-07 22:40:48.860  INFO 14128 --- [           main] com.blog.demo.BlogApplicationTests       : view:UserInfoView{id=14, account='zhangsan', nikeName='张三三', photo='太帅无法显示', about='string', signature='随便想一个签名', likeCount=2, articleCount=4, visitCount=3, fansCount=4}

# 总 #

jpa 其实就是hibernate ,但是实现了java 代码查询单表，复杂查询还是推荐使用原生sql  
多表分页即需原生sql。  
之前我就写过一篇博客记录了在hibernate 中使用了视图-实体映射，现在在jpa由于也是hibernate,那么应该是可以的。

在实现的过程中遇到一个问题：  
擅自更改了数据库一个字段名，同时也将实体中的字段属性也作出了相应更改，但是没有改  
get,set 方法，导致报错：

> javax.persistence.PersistenceException: \[PersistenceUnit: default\] Unable to build Hibernate SessionFactory; nested exception is org.hibernate.MappingException: Could not get constructor for org.hibernate.persister.entity.SingleTableEntityPersister

错误来看是没能创建sesstionfactory,不能找到实体的构造函数额，这个构造可能看的有点疑惑，默认都是有无参构造的，谁能想到是 getXXX方法与属性名不一致导致的

@Column
        public String getSingnature() { // 应该写成getSignature
            return signature;
        }

[20190607223547987.png]: /images/20220121/f7870d56696b471aaf9238cefbda8c21.png