数据库访问中间件--springdata-jpa的基本使用

二、单表SQL操作-使用关键字拼凑方法

回顾

public interface UserRepository extends JpaRepository<User,Integer> {
    
    
    User findByUsernameLike(String username);
}

		@GetMapping("/user/username/{username}")
    public Object findUserByUsername(@PathVariable String username){
    
    
        return userRepository.findByUsernameLike("%"+username+"%");
    }

1、单表sql操作—使用关键词字拼凑的方法

关键字	示例	JPQL 片段
And	findByLastnameAndFirstname	… where x.lastname = ?1 and x.firstname = ?2
Or	findByLastnameOrFirstname	… where x.lastname = ?1 or x.firstname = ?2
Is,Equals	findByFirstnameIs,findByFirstnameEquals	… where x.firstname = ?1
Between	findByStartDateBetween	… where x.startDate between ?1 and ?2
LessThan	findByAgeLessThan	… where x.age < ?1
LessThanEqual	findByAgeLessThanEqual	… where x.age ⇐ ?1
GreaterThan	findByAgeGreaterThan	… where x.age > ?1
GreaterThanEqual	findByAgeGreaterThanEqual	… where x.age >= ?1
After	findByStartDateAfter	… where x.startDate > ?1
Before	findByStartDateBefore	… where x.startDate < ?1
IsNull	findByAgeIsNull	… where x.age is null
IsNotNull,NotNull	findByAge(Is)NotNull	… where x.age not null
Like	findByFirstnameLike	… where x.firstname like ?1
NotLike	findByFirstnameNotLike	… where x.firstname not like ?1
StartingWith	findByFirstnameStartingWith	… where x.firstname like ?1 (parameter bound with appended %)
EndingWith	findByFirstnameEndingWith	… where x.firstname like ?1 (parameter bound with prepended %)
Containing	findByFirstnameContaining	… where x.firstname like ?1 (parameter bound wrapped in %)
OrderBy	findByAgeOrderByLastnameDesc	… where x.age = ?1 order by x.lastname desc
Not	findByLastnameNot	… where x.lastname <> ?1
In	findByAgeIn(Collection ages)	… where x.age in ?1
NotIn	findByAgeNotIn(Collection age)	… where x.age not in ?1
TRUE	findByActiveTrue()	… where x.active = true
FALSE	findByActiveFalse()	… where x.active = false
IgnoreCase	findByFirstnameIgnoreCase	… where UPPER(x.firstame) = UPPER(?1)

2、单表sql操作—使用关键词字拼凑的方法案例

2.1、相关查询题目

●查询出年龄小于等于22岁的人;
●查询出年龄在20- 22岁并且性别是男的人;
●查询出已结婚且性别是男的人;

2.2、表结构

Person
pid varchar(32)
pname varchar(255) unique
psex varchar(255)
page int(3)
getmarried boolean

2.3、注意事项

1. 实体类属性名不要出现isXxx、 getXxx的名称，会导致关键字拼凑出错
2. 实体类属性名中间只要出现了大写字母，就会导致数据库的字段名有下划线隔开，比如你使
   用isMarried属性名，那么实体类的字段名就会变成is_ married, 这样容易导致找不到值
3. 属性名类型是boolean类型的在某些数据库中会变成bit(1)类型， 其中0为false, 1为true

src/main/resources/application.properties

#mysql的配置信息
spring.datasource.url=jdbc:mysql://localhost:3306/test?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&useSSL=true
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

#支持SQL 输出
spring.jpa.show-sql=true
#format 一下 SQL 进行输出
spring.jpa.properties.hibernate.format_sql=true
#自动生成开启，让表数据会自动跟随entity类的变化而变化
#spring.jpa.properties.hibernate.hbm2ddl.auto=update
#开启自动更新，若数据库没有对应的表，则生成，若有，则检查是否需要更改
spring.jpa.hibernate.ddl-auto=update

src/main/java/com/study/springdatajpademosecond/entity/Person.java

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import org.hibernate.annotations.GenericGenerator;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;


@Data//geter、setter、equals、hashcode以及tostring
@Entity
@AllArgsConstructor//全参构造
@NoArgsConstructor//无参构造
@Builder// 部分参数构造
public class Person {
    
    
    @Id
    @GenericGenerator(name = "myuuid",strategy = "uuid")
    @GeneratedValue(generator = "myuuid")
    private String pid;
    @Column(unique = true)
    private String pname;
    @Column
    private String psex;
    @Column
    private Integer page;
    @Column
    private boolean getmarried;
}

src/main/java/com/study/springdatajpademosecond/entity/PersonInfo.java

public interface PersonInfo {
    
    
    String getPid();
    String getPname();
    String getPsex();
    String getPage();
    String getGetmerried();
    Integer getBid();
    String getBname();
    double getBprice();
}

src/main/java/com/study/springdatajpademosecond/repository/PersonRepository.java

import com.study.springdatajpademosecond.entity.Person;
import com.study.springdatajpademosecond.entity.PersonInfo;
import org.springframework.data.jpa.repository.JpaRepository;
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 java.util.List;
import java.util.Map;


public interface PersonRepository extends JpaRepository<Person,String> {
    
    
    //1、查询出年龄小于等于22岁的人；
    List<Person> findAllByPageIsLessThanEqual(Integer age);
    //2、查询出年龄在20-22岁之间并且性别是男的人
    List<Person> findAllByPageBetweenAndPsexEquals(Integer lowage,Integer highage,String sex);
    //3、查询出已经结婚并且性别是男的人
    List<Person> findAllByGetmarriedIsTrueAndPsexEquals(String psex);

}

2.3、测试

@SpringBootTest
class SpringdataJpaDemoSecondApplicationTests {
    
    
    @Resource
    private PersonRepository personRepository;
     @Test
    void contextLoads() {
    
    
      //初始化表
      //  initPersons();
      //1、查询出年龄小于等于22岁的人；
      System.out.println(personRepository.findAllByPageIsLessThanEqual(22));
      System.out.println("---------------------------------------------------");
        //2、查询出年龄在20-22岁之间并且性别是男的人
      System.out.println(personRepository.findAllByPageBetweenAndPsexEquals(20,22,"男"));
      System.out.println("---------------------------------------------------");
        //3、查询出已经结婚并且性别是男的人
       System.out.println(personRepository.findAllByGetmarriedIsTrueAndPsexEquals("男"));
    }
   // 初始化数据库 加入
   private void initPersons() {
    
    
        List<Person> list = new ArrayList<>();
        Collections.addAll(list,
                Person.builder().pname("zhangsan").psex("男").page(22).getmarried(false).build(),
                Person.builder().pname("lisi").psex("女").page(21).getmarried(true).build(),
                Person.builder().pname("wangwu").psex("男").page(20).getmarried(false).build(),
                Person.builder().pname("zhaoliu").psex("女").page(23).getmarried(true).build(),
                Person.builder().pname("sunqi").psex("男").page(25).getmarried(true).build());
        personRepository.saveAll(list);
    }
}

三、单表SQL操作-使用关键字拼凑方法无法解决的问题及解决方法

1、造成的原因

• 实体类的属性名与表的字段名无法映射，导致关键字找不到
• CRUD操作方式比较另类或者是你不想用关键字的写法
• 涉及到了多表操作

2、解决方法

2.1、使用sql语句来书写sql

2.2、使用hql语句来书写sql

具体看文档

3、演示使用sql语句来书写sql

3.1、 实现接口

public interface PersonRepository extends JpaRepository<Person,String> {
    
    

    //4、根据pname来模糊删除一个person数据
    @Transactional
    @Modifying
    @Query(value = "delete from Person where pname like %:pname%")
    void deleteByName(@Param("pname") String pname);
    //5、使用HQL或者是sql来书写一个查询语句，查询出年龄在20-22岁，性别是女的人
//    @Query(value = "select * from person where page between 20 and 22 and psex='女'",nativeQuery = true)
    @Query(value = "select p from Person p where p.page between 20 and 22 and p.psex='女'")
    List<Person> findPerson();
    //6、使用SPEL表达式来完成person表的修改操作
    @Modifying
    @Transactional
    @Query(value = "update person set pname=:#{#person.pname},psex=:#{#person.psex},page=:#{#person.page} " +
            "where pid=:#{#person.pid}",nativeQuery = true)
    void updatePerson(@Param("person") Person person);
}

3.2、测试

    private void createSqlTest() {
    
    
        //        personRepository.deleteByName("si");
//        System.out.println(personRepository.findPerson());
        personRepository.updatePerson(Person.builder().pid("402882f870e8a2cd0170e8a2d6470002").
                pname("刘德华").psex("男").page(60).build());
    }

四、Spring data jpa逆向工程和多表查询

1、三种形式

VO不讲解

2、Spring data jpa逆向操作

2.1、关联数据库

idea右侧 —database—±–data source —HSQLDB

url 填写jdbc:mysql://localhost:3306/test?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&useSSL=true

然后测试

2.2、逆向生成

idea 右侧的project structure—project settigns----Modules—JPA—±-选择默认

idea 左侧的persistence —

选择entity包

然后选中book 逆向生成

这时候就能生成实体类了

3、多表查询

3.1、联表查询-根据书名来查该书籍的拥有者

 //7、联表查询-根据书名来查该书籍的拥有者
    @Query(value = "select p from Person p inner join Book b on p.pid=b.pid where b.bname=:bname")
    Person findPersonByBname(@Param("bname") String bname);

     //测试 7、联表查询-根据书名来查该书籍的拥有者
     System.out.println(personRepository.findPersonByBname("三国演义"));

3.2、联表查询-联表查询-根据用户id来查询person和book

3.2.1、创建接口形式

1、创建接口

创建PersonInfo是为了展示person和book需要展示的部分

public interface PersonInfo {
    
    
    String getPid();
    String getPname();
    String getPsex();
    String getPage();
    String getGetmerried();
    Integer getBid();
    String getBname();
    double getBprice();
}

2、具体查询

    @Query(value = "select p.pid as pid,p.pname as pname,p.psex as psex,p.getmarried as getmarried," +
            "b.bid as bid,b.bname as bname,b.bprice as bprice from Person p inner join Book b on p.pid=b.pid " +
            "where p.pid=:pid")
    List<PersonInfo> findAllInfo(@Param("pid") String pid);

一定要使用别名

List<PersonInfo> allInfo = personRepository.findAllInfo("402882f870e8a2cd0170e8a2d6470002");
        for (PersonInfo info:allInfo
             ) {
    
    
            System.out.println(info.getPid()+","+info.getPname()+","+info.getPsex()+","+info.getPage()+","+info.getGetmarried()+","+
                    info.getBid()+","+info.getBname()+","+info.getBprice());
        }

3.2.2、通过集合形式

 //使用集合来接收数据-List<Map<>>     System.out.println(personRepository.findAllInfo2("402882f870e8a2cd0170e8a2d6470002"));
    //通过集合来接收数据-list
   List<Object> allInfo1 = personRepository.findAllInfo1("402882f870e8a2cd0170e8a2d6470002");
        Object[] o = (Object[])allInfo1.get(0);
        System.out.println(Arrays.toString(o));

五、Query-DSL