JPA訪問數據庫的幾種方式
本文為原創，轉載請注明出處：https://www.cnblogs.com/supiaopiao/p/10901793.html
1. Repository
1.1. 通過方法名稱直接生成查詢
| Keyword |
Sample |
JPQL snippet |
| And |
findByLastnameAndFirstname |
… where x.lastname = ?1 and x.firstname = ?2 |
| Or |
findByLastnameOrFirstname |
… where x.lastname = ?1 or x.firstname = ?2 |
| Is,Equals |
findByFirstname,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<Age> ages) |
… where x.age in ?1 |
| NotIn |
findByAgeNotIn(Collection<Age> ages) |
… 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) |
In和NotIn可以使用任何Collection的子類作為參數。
案例：
| public interface UserRepository extends JpaRepository<User, Integer>, JpaSpecificationExecutor<User> {
Page<User> findByName(String name);
List<User> findByNameAndPhone(String name, String phone);
User findUserById(Integer id);
void deleteByIdIn(List<Integer> idList);
}
|
1.2. @Query注解
可以使用Spring Data JPA 的@Query注解將查詢綁定到repository的函數上。
備注：注解到查詢方法上的@Query執行順序優先於下文中的@NamedQuery。
1.2.1. HQL
注意：使用“:屬性名”的時候，最好在接口上加上@Param注解，否則會報類似如下異常：
| public interface UserRepository extends JpaRepository<User, Integer>{
@Query(value = "SELECT u FROM User u WHERE u.name like %?1%")//不加nativeQuery應使用HQL
List<User> findTable2(String name); @Query(value = "SELECT u FROM User u WHERE u.name like %:name% and u.sex = :sex")
List<User> findTable3(@Param("name") String name, @Param("sex")String sex);
} |
1.2.2. 原生SQL
（1）@Query注解通過設置nativeQuery標識支持執行原生SQL查詢語句
| public interface UserRepository extends JpaRepository<User, Integer>{
@Query(value = "SELECT * FROM user WHERE name like %?1%", nativeQuery = true)
List<User> findTable1(String name); } |
（2）Spring Data JPA通過原生SQL進行查詢時，不能滿足Page條件進行分頁，所以可以通過countQuery標識執行count查詢實現Page分頁：
| public interface UserRepository extends JpaRepository<User, Integer>{
@Query(value = "SELECT * FROM user WHERE name like %?1%",
countQuery = "SELECT count(*) FROM user WHERE name like %?1%",
nativeQuery = true)
Page<User> findTable3(String name, Pageable pageable);
} |
1.3. @Modifying注解
- 在@Query注解中編寫JPQL實現DELETE和UPDATE操作的時候必須加上@Modifying注解，以通知Spring Data這是一個DELETE或UPDATE操作。
- UPDATE或者DELETE操作需要使用事務，此時需要定義Service層，在Service層的方法上添加事務操作@Transactional。
- Modifying查詢語句中能用於void/int/Integer 返回類型，不能用於其他類型
- 注意JPQL不支持INSERT操作。
代碼示例：
| public interface UserRepository extends JpaRepository<User, Integer>{ @Modifying
@Query("UPDATE User u SET u.name = :name WHERE u.id = :id")
void updateTable(@Param("name") String name, @Param("id")Integer id); @Modifying
@Query("delete from User u WHERE u.id in :idList")
void deleteByIds(@Param("idList")List<Integer> idList); } |
2. 實體類中定義，在Repository中使用
2.1. 命名查詢@NamedQuery
使用@NamedQuery為實體創建查詢適用於定義少量查詢。@NamedQuery需要聲明在實體類上，@NamedQuery可以實現命名HQL查詢（或JPQL）。
備注：注解到查詢方法上的@Query（上文中）執行順序優先於@NamedQuery。
| @Entity
@NamedQuery(name = "Two.selectBySex",query = "select t from Two t where t.sex = ?1 group by id")
public class Two {
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="id",nullable=false)
private Integer id;
@Column(name="name",nullable=false)
private String name;
@Column(name="sex",nullable=false)
private String sex; Set、get方法省略
} |
Repository層代碼展示：
| public interface TwoRepository extends JpaRepository<Two, Integer>{
//實體類上通過@NamedQuery注解實現查詢
List<Two> selectBySex(String sex);
} |
Spring Data處理這些方法對命名查詢的調用，以實體類名稱開始，后接方法名，以點作連接符。所以NameQuery定義在實體上，而不是定義在方法上。
2.2. 一個實體類中有多個命名查詢@NamedQueries
上面我們演示了命名查詢@NamedQuery的寫法，當然JPA也支持多個@NamedQuery，那就是@NamedQueries
| @Entity
@NamedQueries(value = {
@NamedQuery(
name = "Two.selectBySex",
query = "select t from Two t where t.sex = ?1 group by id"),
@NamedQuery(
name = "Two.findUserByPrimaryKey",
query = "select t from Two t where t.id = :id")
}) public class Two {
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="id",nullable=false)
private Integer id;
@Column(name="name",nullable=false)
private String name;
@Column(name="sex",nullable=false)
private String sex; Set、get方法省略
} |
Repository層代碼展示：
| public interface TwoRepository extends JpaRepository<Two, Integer>{
//實體類上通過@NamedQuery注解實現查詢
List<Two> selectBySex(String sex);
Two findUserByPrimaryKey(@Param("id") Integer id);
} |
Spring Data處理這些方法對命名查詢的調用，以實體類名稱開始，后接方法名，以點作連接符。所以NameQuery定義在實體上，而不是定義在方法上。
2.3. 命名原生sql查詢@NamedNativeQuery
@NamedNativeQuery可以實現命名原生sql查詢
| @Entity
@NamedNativeQuery(name = "Three.selectBySex", query = "select * from three where sex = ?1 group by id", resultClass = Three.class)
@Table(name="three")
public class Three {
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="id",nullable=false)
private Integer id;
@Column(name="name",nullable=false)
private String name;
@Column(name="sex",nullable=false)
private String sex; Set、get方法省略
} |
Repository層代碼展示：
| public interface ThreeRepository extends JpaRepository<Three, Integer>{
//實體類上通過@NamedNativeQuery注解實現查詢
List<Three> selectBySex(String sex);
} |
2.4. 一個實體類中有多個命名查詢@NamedNativeQueries
上面我們演示了命名查詢@NamedNativeQuery的寫法，當然JPA也支持多個@NamedNativeQuery，那就是@NamedNativeQueries
| @Entity
@NamedNativeQueries(value = {
@NamedNativeQuery(
name = "Three.selectBySex",
query = "select * from three where sex = ?1 group by id",
resultClass = Three.class),
@NamedNativeQuery(
name = "Three.findUserByPrimaryKey",
query = "select * from three where id = :id",
resultClass = Three.class)//resutlClass用來指定實體類，resutlSetMapping用來指定映射的名稱
})
@Table(name="three")
public class Three {
@Id @GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="id",nullable=false)
private Integer id;
@Column(name="name",nullable=false)
private String name;
@Column(name="sex",nullable=false)
private String sex; Set、get方法省略
} |
Repository層代碼展示：
| public interface ThreeRepository extends JpaRepository<Three, Integer>{
//實體類上通過@NamedNativeQuery注解實現查詢
List<Three> selectBySex(String sex);
Three findUserByPrimaryKey(@Param("id") Integer id);
} |
3. 外部ORM文件中定義，在Repository中使用
3.1. 命名查詢named-query
使用XML配置，向位於resources/META-INF文件夾下的orm.xml配置文件添加必要的<name-query/>元素。
resources/META-INF下orm.xml配置：
| <?xml version="1.0" encoding="UTF-8" ?>
<entity-mappings xmlns="http://xmlns.jcp.org/xml/ns/persistence/orm"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence/orm
http://xmlns.jcp.org/xml/ns/persistence/orm_2_0.xsd" version="2.1">
<!-- JPA Named Queries -->
<named-query name="One.selectByName">
<query>SELECT o FROM One o WHERE o.sex = ?1 group by id</query>
</named-query>
<named-query name="One.findUserByPrimaryKey">
<query>SELECT o FROM One o WHERE o.id = :id</query>
</named-query>
</entity-mappings> |
Repository層代碼展示：
| public interface OneRepository extends JpaRepository<One, Integer>{
//1.1 XML定義 命名查詢
List<One> selectByName(String name);
One findUserByPrimaryKey(@Param("id") Integer id);
} |
3.2. 原生SQL查詢named-native-query
使用XML配置，向位於resources/META-INF文件夾下的orm.xml配置文件添加必要的<named-native-query/>元素。
resources/META-INF下orm.xml配置：
| <?xml version="1.0" encoding="UTF-8" ?>
<entity-mappings xmlns="http://xmlns.jcp.org/xml/ns/persistence/orm"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence/orm
http://xmlns.jcp.org/xml/ns/persistence/orm_2_0.xsd" version="2.1">
<!-- JPA Named Native Queries -->
<named-native-query name="One.selectByName1">
<query>SELECT * FROM one WHERE sex = ?1 group by id</query>
</named-native-query> <!--result-class用來指定實體類，result-set-mapping用來指定映射的名稱-->
<named-native-query name="One.findUserByPrimaryKey1" result-class="cn.com.bmsoft.stormplan.basic.entity.One">
<query>SELECT * FROM one WHERE id = :id</query>
</named-native-query>
</entity-mappings> |
Repository層代碼展示：
| package cn.com.bmsoft.stormplan.basic.dao;
import cn.com.bmsoft.stormplan.basic.entity.One;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.repository.query.Param;
import java.util.List;
public interface OneRepository extends JpaRepository<One, Integer>{
//1.2 XML定義 原生sql查詢 named-native-query
List<One> selectByName1(String sex);
One findUserByPrimaryKey1(@Param("id")Integer id);
} |
4. SpEL表達式
從Spring Data JPA 1.4版本開始，支持在@Query定義的查詢中使用SpEL模板表達式。在執行查詢的時候，這些表達式通過一個事先定義好的變量集合求值。Spring Data JPA支持一個名為entityName的變量。它的用法是select x from #{#entityName} x。它會將域類型的entityName與給定repository關聯起來。entityName按照如下方式處理：如果域類型在@Entity注解上設置了name屬性，則使用該屬性。否則直接使用域類型的類名。
下例演示了在定義帶有查詢方法和手工定義查詢的repository接口時使用#{#entityName}表達式。
| public interface UserRepository extends JpaRepository<User, Integer>{
@Query(value = "SELECT u FROM #{#entityName} u WHERE u.name like %:name% and u.sex = :sex")
List<User> findTable4(@Param("name") String name, @Param("sex")String sex);
} |
SpEL表達式的好處：
參考網址：https://www.cnblogs.com/tilv37/p/6944182.html
5. Specifications動態構建查詢
5.1. 參數介紹
- Predicate:單獨每一條查詢條件的詳細描述
Predicate[]:多個查詢條件的詳細描述
- Root：查詢哪個表
- CriteriaQuery：查詢哪些字段，排序是什么
- CriteriaBuilder：字段之間是什么關系，如何生成一個查詢條件，每個查詢條件都是什么方式
（1）CriteriaQuery<T>:主要是構建查詢條件
distinct、select、where、groupby、having、orderby等
（2）CriteriaBuilder:主要是用來進行一些函數操作
① and
② or
③ between
④ lt（小於）、le（小於等於）、gt（大於）、ge（大於等於）
⑤ not（非）等...
5.2. 代碼案例
//where empname like ? group by wages
| @Override
public Page<EmployeeEntity> search1(EmployeeVO employeeVO) throws Exception {
Pageable pageable = PageRequest.of(employeeVO.getPage() - 1, employeeVO.getSize(), Sort.Direction.ASC,"empid");
Specification<EmployeeEntity> specification = new Specification<EmployeeEntity>() {
@Override
public Predicate toPredicate(Root<EmployeeEntity> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder cb) {
List<Predicate> list = new ArrayList<>(10);
if(StringUtils.isNotBlank(employeeVO.getEmpname())){
list.add(cb.and(
cb.like(root.get("empname").as(String.class),"%"+ employeeVO.getEmpname()+"%")
));
}
Expression<BigDecimal> wages = root.get("wages").as(BigDecimal.class);
return criteriaQuery.where(list.toArray(new Predicate[list.size()])).groupBy(wages).getRestriction();
//where empname like ? group by wages
}
};
Page<EmployeeEntity> stuPage = employeeRepository.findAll(specification, pageable);
return stuPage;
} |
//where empname like ? or deptid=?
| @Override
public Page<EmployeeEntity> search2(EmployeeVO employeeVO) throws Exception {
Pageable pageable = PageRequest.of(employeeVO.getPage() - 1, employeeVO.getSize(), Sort.Direction.ASC,"empid");
Specification<EmployeeEntity> specification = new Specification<EmployeeEntity>() {
@Override
public Predicate toPredicate(Root<EmployeeEntity> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder cb) {
List<Predicate> list = new ArrayList<>(10);
if(StringUtils.isNotBlank(employeeVO.getEmpname()) && null != employeeVO.getDeptid()){
list.add(cb.or(
cb.like(root.get("empname").as(String.class),"%"+ employeeVO.getEmpname()+"%"),
cb.equal(root.get("deptid").as(Integer.class), employeeVO.getDeptid())
));
}//where empname like ? or deptid=?
return criteriaQuery.where(list.toArray(new Predicate[list.size()])).getRestriction();
}
};
Page<EmployeeEntity> stuPage = employeeRepository.findAll(specification, pageable);
return stuPage;
} |
//where wages < ?
| @Override
public Page<EmployeeEntity> search3(EmployeeVO employeeVO) throws Exception {
Pageable pageable = PageRequest.of(employeeVO.getPage() - 1, employeeVO.getSize(), Sort.Direction.ASC,"empid");
Specification<EmployeeEntity> specification = new Specification<EmployeeEntity>() {
@Override
public Predicate toPredicate(Root<EmployeeEntity> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder cb) {
Predicate wages = cb.lt(root.get("wages").as(BigDecimal.class), employeeVO.getWages());
return criteriaQuery.where(wages).getRestriction();
}
};//where wages < ?
Page<EmployeeEntity> stuPage = employeeRepository.findAll(specification, pageable);
return stuPage;
} |
//where wages between ? and ?
| @Override
public Page<EmployeeEntity> search4(EmployeeVO employeeVO){
Pageable pageable = PageRequest.of(employeeVO.getPage() - 1, employeeVO.getSize(), Sort.Direction.ASC,"empid");
Specification<EmployeeEntity> specification = new Specification<EmployeeEntity>() {
@Override
public Predicate toPredicate(Root<EmployeeEntity> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder cb) {
Predicate wages = cb.between(root.get("wages").as(BigDecimal.class), employeeVO.getMinWages(), employeeVO.getMaxWages());
return criteriaQuery.where(wages).getRestriction();
}
};//where wages between ? and ?
Page<EmployeeEntity> stuPage = employeeRepository.findAll(specification, pageable);
return stuPage;
} |
6. JPA Join聯表查詢
構建表關系如下：
實體類代碼展示：
| @Entity
@Table(name="a")
public class AEntity {
@Id
@GeneratedValue(strategy= GenerationType.IDENTITY)
@Column(name="aid",nullable=false)
private Integer aid;
@Column(name="aname",nullable=false)
private String aname; 省略set、get方法
} |
@Entity
@Table(name="b")
public class BEntity {
@Id
@GeneratedValue(strategy= GenerationType.IDENTITY)
@Column(name="bid",nullable=false)
private Integer bid;
@Column(name="bname",nullable=false)
private String bname;
@OneToOne(cascade=CascadeType.ALL) //B是關系的維護端，當刪除 b，會級聯刪除 a
@JoinColumn(name = "aid", referencedColumnName = "aid") //name：關聯id，referencedColumnName：A表id
private AEntity aEntity;//A表 省略set、get方法
} |
| @Entity
@Table(name="c")
public class CEntity {
@Id
@GeneratedValue(strategy= GenerationType.IDENTITY)
@Column(name="cid",nullable=false)
private Integer cid;
@Column(name="cname",nullable=false)
private String cname;
省略set、get方法 } |
@Entity
@Table(name="d")
public class DEntity {
@Id
@GeneratedValue(strategy= GenerationType.IDENTITY)
@Column(name="did",nullable=false)
private Integer did;
@Column(name="dname",nullable=false)
private String dname;
//可選屬性optional=false,表示B不能為空。刪除d，不影響b @ManyToOne(cascade={CascadeType.MERGE,CascadeType.REFRESH},optional=false)
@JoinColumn(name = "bid", referencedColumnName = "bid")//name：關聯id，referencedColumnName：B表id
private BEntity bEntity;//B表
//可選屬性optional=false,表示C不能為空。刪除d，不影響c
@ManyToOne(cascade={CascadeType.MERGE,CascadeType.REFRESH},optional=false)
@JoinColumn(name = "cid", referencedColumnName = "cid")//name：關聯id，referencedColumnName：C表id
@JsonBackReference
private CEntity cEntity;//C表
省略set、get方法
} |
Service層代碼展示：
| @Override
public Page<DEntity> search(DVO dVO) {
Pageable pageable = PageRequest.of(dVO.getPage() - 1, dVO.getSize(), Sort.Direction.ASC,"did");
Specification<DEntity> specification = new Specification<DEntity>() {
@Override
public Predicate toPredicate(Root<DEntity> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder cb) {
List<Predicate> list = new ArrayList<>(10);
//A:B:D 1:1:n 根據D的實體類查詢aname
if (StringUtils.isNotBlank(dVO.getAname())) {
Join<AEntity,DEntity> ajoin = root.join("bEntity",JoinType.LEFT);
list.add(cb.like(ajoin.get("aEntity").get("aname").as(String.class),"%"+ dVO.getAname()+"%"));
}//select * from d left join b on d.bid=b.bid left join a on b.aid=a.aid where a.aname like "%xxx%"
//B:D 1:n 根據D的實體類查詢bname
if (StringUtils.isNotBlank(dVO.getBname())) {
Join<BEntity,DEntity> ajoin = root.join("bEntity",JoinType.LEFT);
list.add(cb.like(ajoin.get("bname").as(String.class),"%"+ dVO.getBname()+"%"));
}//select * from d left join b on d.bid=b.bid where b.bname like "%xxx%"
//C:D 1:n 根據D的實體類查詢cname
if (StringUtils.isNotBlank(dVO.getCname())) {
Join<BEntity,DEntity> ajoin = root.join("cEntity",JoinType.LEFT);
list.add(cb.like(ajoin.get("cname").as(String.class),"%"+ dVO.getCname()+"%"));
}//select * from d left join c on d.cid=c.cid where c.cname like "%xxx%"
return criteriaQuery.where(list.toArray(new Predicate[list.size()])).getRestriction();
}
};
Page<DEntity> stuPage = dRepository.findAll(specification, pageable);
return stuPage;
} |
