Spring data jpa使用

一、添加依赖

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

二、基本CRUD

1.在Dao层创建接口

public interface LabelDao extends JpaRepository<Label, String>, JpaSpecificationExecutor<Label> {
}

2.该接口继承了jpa，所以自带了基本增删改查功能

labelDao.findAll(); //查所有
labelDao.findById(id); //根据id查
labelDao.save(label);//如果在数据库中主键不存在，save方法会执行添加操作，如果主键在数据库中已存在，save方法会执行更新操作
labelDao.deleteById(id); //根据id删

三、创建pojo。其中的注解都在javax.persistence包下 

@Entity
@Table(name = "tb_pl")
public class Pl implements Serializable {
    @Id //联合主键
    private String problemid;
    @Id //联合主键
    private String labelid;

    public String getProblemid() {
        return problemid;
    }

    public void setProblemid(String problemid) {
        this.problemid = problemid;
    }

    public String getLabelid() {
        return labelid;
    }

    public void setLabelid(String labelid) {
        this.labelid = labelid;
    }
}

四、自定义方法名查询

sprngdatajpa根据你按命名规则定义的方法名自动进行条件查询。例：

public interface RecruitDao extends JpaRepository<Recruit, String>, JpaSpecificationExecutor<Recruit> {
    /**
     * 根据状态按时间倒序查职位列表（查6个）
     *
     * @param state
     * @return
     */
    public List<Recruit> findTop6ByStateOrderByCreatetimeDesc(String state);

    /**
     * 根据反状态按时间倒序查职位列表（查12个）
     *
     * @param state
     * @return
     */
    public List<Recruit> findTop12ByStateNotOrderByCreatetimeDesc(String state, Pageable pageable); //只要在方法参数加上Pageable类型的形参就能实现分页查询
　　//Pageable对象一般通过PageRequest.of(int page, int size)方法创建，其中page默认从0开始
}

 命名规则表：

关键字	方法命名	sql where字句
And	findByNameAndPwd	where name= ? and pwd =?
Or	findByNameOrSex	where name= ? or sex=?
Is,Equals	findById,findByIdEquals	where id= ?
Between	findByIdBetween	where id between ? and ?
LessThan	findByIdLessThan	where id < ?
LessThanEquals	findByIdLessThanEquals	where id <= ?
GreaterThan	findByIdGreaterThan	where id > ?
GreaterThanEquals	findByIdGreaterThanEquals	where id > = ?
After	findByIdAfter	where id > ?
Before	findByIdBefore	where id < ?
IsNull	findByNameIsNull	where name is null
isNotNull,NotNull	findByNameNotNull	where name is not null
Like	findByNameLike	where name like ?
NotLike	findByNameNotLike	where name not like ?
StartingWith	findByNameStartingWith	where name like '?%'
EndingWith	findByNameEndingWith	where name like '%?'
Containing	findByNameContaining	where name like '%?%'
OrderBy	findByIdOrderByXDesc	where id=? order by x desc
Not	findByNameNot	where name <> ?
In	findByIdIn(Collection<?> c)	where id in (?)
NotIn	findByNameNot	where name <> ?
True	findByAaaTue	where aaa = true
False	findByAaaFalse	where aaa = false
IgnoreCase	findByNameIgnoreCase	where UPPER(name)=UPPER(?)
top	findTop100	top 10/where ROWNUM <=10

 五、原生使用sql操作数据库

/**
     * 查询
     *
     * @param labelId
     * @param pageable
     * @return
     */
    @Query(value = "select * from tb_problem p, tb_pl pl where p.id = pl.problemid and pl.labelid = ?1 order by p.updatetime desc", nativeQuery = true)
    public Page<Problem> findNewProblemsByLabelId(String labelId, Pageable pageable);

 其中1代表传入的第一个参数，以此类推

/**
     * 修改
     *
     * @param articleId
     */
    @Modifying
    @Query(value = "update tb_article set state = 1 where id = ?", nativeQuery = true)
    public void examine(String articleId);