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