前期回顾

ORM解决方案

框架名称	所属公司	适用场合
Hibernate	创始人：Gavin King 公司：JBOSS 所有	适用与需求变化不多的中小型项目中，比如后台管理系统
Mybatis	Apache社区	适用于表关联较多的项目，持续维护开发迭代较快的项目，需求变化较多的项目，如互联网项目
Mybatis-Plus	苞米豆社区, 为猿类崛起而生	MyBatis-Plus是一个 MyBatis的增强工具，在 MyBatis 的基础上只做增强不做改变，为简化开发、提高效率而生。
Spring Data JPA	Spring的母公司是VMware	传统项目或者关系模型较为清晰稳定的项目，建议JPA

JPA

简介

• JPA是Java Persistence API的简称，中文名Java持久层API，是Sun公司在JDK5.0后提出的一套基于ORM的Java持久化规范。它为Java开发人员提供了一种对象/关联映射工具来管理Java应用中的关系数据。
• Sun公司引入新的JPA ORM规范出于两个原因：
  • 其一，简化现有Java EE和Java SE应用开发工作；
  • 其二，结束Hibernate、TopLink、JDO等ORM框架各自为营的局面。Sun公司希望整合ORM技术，实现天下归一；
• JPA是在吸收现有ORM框架的基础上发展而来，具有易于使用，伸缩性强等优点。
• 由于JPA只是一个规范，它本身不执行任何操作。 它需要一个实现。 因此，像Hibernate，TopLink和iBatis这样的ORM工具实现了JPA数据持久性规范。
• JSR 338，详细内容可参考：https://github.com/javaee/jpa-spec）

JPA的组成技术

ORM映射元数据

• JPA支持XML和JDK5.0注解两种元数据的形式，元数据描述对象和表之间的映射关系，框架据此将实体对象持久化到数据库表中；

Java持久化API

• 用来操作实体对象，执行CRUD操作，框架在后台替代我们完成所有的事情，开发者从繁琐的JDBC和SQL代码中解脱出来。

查询语言（JPQL）

• 这是持久化操作中很重要的一个方面，通过面向对象的查询语言查询数据，避免程序和SQL语句紧密耦合。

JPA的优势

1. 简化开发：Jpa提供了一种面向对象的方式来进行数据库操作，开发人员可以使用Java对象来表示数据库表和记录，而不需要编写复杂的SQL语句。这样可以大大简化开发过程，提高开发效率。
2. 高度抽象：Jpa提供了一套高度抽象的API，隐藏了底层数据库的细节，开发人员可以更加专注于业务逻辑的实现，而不需要关注数据库的具体实现细节。这样可以降低开发的复杂性，提高代码的可维护性。
3. 跨数据库支持：Jpa支持多种数据库，开发人员可以在不同的数据库之间切换，而不需要修改大量的代码。这样可以提高系统的灵活性和可扩展性。
4. 自动化的事务管理：Jpa提供了自动化的事务管理机制，开发人员可以使用注解来标识事务的边界，Jpa会自动处理事务的提交和回滚。这样可以简化事务管理的代码，提高系统的稳定性和可靠性。

JPA的缺点

1. 学习成本较高：Jpa是一种复杂的技术，需要开发人员具备一定的数据库和ORM（对象关系映射）的知识。对于初学者来说，学习和掌握Jpa可能需要一定的时间和精力。
2. 性能问题：由于Jpa是一种高度抽象的技术，它会对数据库的访问和操作进行一定的封装和转换，这可能会导致一定的性能损失。在对性能要求较高的场景下，可能需要使用原生的SQL语句来进行数据库操作。
3. 灵活性受限：Jpa提供了一套标准的API，开发人员需要按照这套API来进行开发，这可能会限制一些特定的需求和场景。在一些复杂的业务场景下，可能需要使用原生的SQL语句或其他ORM框架来实现。

Spring Data JPA

Spring Data JPA简介

• 官网：https://spring.io/projects/spring-data-jpa
• Spring Data JPA是Spring Data家族的一部分，可以轻松实现基于JPA的存储库。 此模块处理对基于JPA的数据访问层的增强支持。 它使构建使用数据访问技术的Spring驱动应用程序变得更加容易。
• Spring Data JPA 是 Spring 基于 ORM 框架、JPA 规范的基础上封装的一套JPA应用框架，可使开发者用极简的代码即可实现对数据的访问和操作。它提供了包括增删改查等在内的常用功能，且易于扩展。
• 在相当长的一段时间内，实现应用程序的数据访问层一直很麻烦。 必须编写太多样板代码来执行简单查询以及执行分页和审计。 Spring Data JPA旨在通过减少实际需要的工作量来显著改善数据访问层的实现。

Spring Data 家族

• Spring Data的官网：http://projects.spring.io/spring-data/
• Spring Data是Spring的一个子项目，旨在统一和简化各类型的持久化存储方式，而不拘泥于是关系型数据库还是NoSQL数据库。
• Spring Data 的使命是给各种数据访问提供统一的编程接口，从而简化开发人员的代码，提高开发效率。
• 无论是哪种持久化存储方式，数据库访问对象都会提供对对象的增加、删除、修改和查询的方法，以及排序和分页方法等。
  

Spring Data JPA、JPA和其他框架之间的关系

• JPA是一套规范，而不是具体的ORM框架。
• Hibernate、TopLink等是JPA规范的具体实现，这样的好处是开发者可以面向JPA规范进行持久层的开发，而底层的实现则是可以切换的。
• Spring Data Jpa则是在JPA之上添加另一层抽象，极大地简化持久层开发及ORM框架切换的成本
  

SpringBoot整合JPA

JPA的核心注解

1.依赖

		<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!--数据库驱动--><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.47</version></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency>

2.添加配置

server:port: 9999
spring:datasource:driver-class-name: com.mysql.jdbc.Driverurl: jdbc:mysql://localhost:3306/smbms?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=Asia/Shanghaiusername: rootpassword: 123456type: com.zaxxer.hikari.HikariDataSourcejpa:hibernate:ddl-auto: updatenaming:physical-strategy: org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImplshow-sql: truedatabase-platform: org.hibernate.dialect.MySQL5InnoDBDialect

3.实体类

java">package cn.smbms.pojo;import lombok.Data;
import org.springframework.format.annotation.DateTimeFormat;import javax.persistence.*;
import java.util.Date;/*** @author: zjl* @datetime: 2024/4/23* @desc:*/
@Data
@Table(name = "smbms_user")
@Entity
public class User {@Id@Column(name = "id")@GeneratedValue(strategy = GenerationType.AUTO)private Integer id;@Column(name = "userCode")private String userCode;private String userName;private String userPassword;private Integer gender;@DateTimeFormat(pattern = "yyyy-MM-dd")private Date birthday;@Column(name = "phone",nullable = false)private String phone;private String address;@Column(name = "userRole",updatable = false)private Integer userRole;private Integer createdBy;@DateTimeFormat(pattern = "yyyy-MM-dd")private Date creationDate;private Integer modifyBy;@DateTimeFormat(pattern = "yyyy-MM-dd")private Date modifyDate;
}

4.创建数据访问层接口继承自JpaRepository<T, ID>接口

• JpaRepository拥有基本CRUD功能以及分页功能
  

• JpaRepository继承自PagingAndSortingRepository。
  

  • 分页接口和实现类
    • Pageable 是Spring Data库中定义的一个接口，用于构造翻页查询，是所有分页相关信息的一个抽象，通过该接口，我们可以得到和分页相关所有信息（例如pageNumber、pageSize等），这样，Jpa就能够通过Pageable参数来得到一个带分页信息的Sql语句
    • PageRequest：Pageable接口的实现类
    • Page接口：用于储存查询的结果集
  • 排序

• 泛型 T 为任意实体对象，ID为主键的数据类型

java">public interface UserRepository extends JpaRepository<User, Integer> {
}

5.添加用户业务实现类

java">@Service
public class UserService {@Resourceprivate UserRepository userRepository;public User saveOrUpdate(User user){User saveUser = userRepository.save(user);return saveUser;}
}

6.测试

测试添加

• 因为设置了主键ID的策略为自增，因此不用传ID就会执行添加操作。
• 也可以传一个不存在的ID，也会执行新增操作，但是主键并不是自定义的主键值，而是自增的主键值

java">@SpringBootTest
class JpabootApplicationTests {@Resourceprivate UserService userService;@Testvoid saveOrUpdate() {User user = new User();user.setUserName("薇恩");user.setUserCode("VN");user.setAddress("下路");user.setPhone("180xxxx4568");user.setUserRole(3);User saveResult = userService.saveOrUpdate(user);System.out.println(saveResult);}
}

• 执行结果如下：

  java">Hibernate: select next_val as id_val from hibernate_sequence for update
  Hibernate: update hibernate_sequence set next_val= ? where next_val=?
  Hibernate: insert into smbms_user (address, birthday, createdBy, creationDate, gender, modifyBy, modifyDate, phone, userCode, userName, userPassword, userRole, id) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
  User(id=31, userCode=VN, userName=暗夜射手, userPassword=null, gender=null, birthday=null, phone=180xxxx4568, address=下路, userRole=3, createdBy=null, creationDate=null, modifyBy=null, modifyDate=null)
  

如果不传phone的话，会报错，提示phone属性不能为空

测试修改

• 传一个已存在的ID，会触发修改，若属性为空，会将对应的字段值也修改为空，因此需要特别注意

java">    @Testvoid saveOrUpdate() {User user = new User();user.setId(31);user.setUserName("暗夜射手");user.setUserCode("VN");//user.setAddress("下路");user.setPhone("180xxxx4568");user.setUserRole(3);User saveResult = userService.saveOrUpdate(user);System.out.println(saveResult);}

• 因为userRole设置了updatable = false，因此数据中这个字段的值还会是3，而不是2
• 执行结果如下：

  java">Hibernate: select user0_.id as id1_0_0_, user0_.address as address2_0_0_, user0_.birthday as birthday3_0_0_, user0_.createdBy as createdb4_0_0_, user0_.creationDate as creation5_0_0_, user0_.gender as gender6_0_0_, user0_.modifyBy as modifyby7_0_0_, user0_.modifyDate as modifyda8_0_0_, user0_.phone as phone9_0_0_, user0_.userCode as usercod10_0_0_, user0_.userName as usernam11_0_0_, user0_.userPassword as userpas12_0_0_, user0_.userRole as userrol13_0_0_ from smbms_user user0_ where user0_.id=?
  Hibernate: update smbms_user set address=?, birthday=?, createdBy=?, creationDate=?, gender=?, modifyBy=?, modifyDate=?, phone=?, userCode=?, userName=?, userPassword=? where id=?
  User(id=31, userCode=VN, userName=暗夜射手, userPassword=null, gender=null, birthday=null, phone=180xxxx4568, address=null, userRole=3, createdBy=null, creationDate=null, modifyBy=null, modifyDate=null)
  

测试简单查询

service层

java">    public User findUserById(Integer id){return userRepository.findById(id).get();}

测试

java">    @Testvoid findUserById() {User user = userService.findUserById(1);System.out.println(user);}

执行结果如下：

java">Hibernate: select user0_.id as id1_0_0_, user0_.address as address2_0_0_, user0_.birthday as birthday3_0_0_, user0_.createdBy as createdb4_0_0_, user0_.creationDate as creation5_0_0_, user0_.gender as gender6_0_0_, user0_.modifyBy as modifyby7_0_0_, user0_.modifyDate as modifyda8_0_0_, user0_.phone as phone9_0_0_, user0_.userCode as usercod10_0_0_, user0_.userName as usernam11_0_0_, user0_.userPassword as userpas12_0_0_, user0_.userRole as userrol13_0_0_ from smbms_user user0_ where user0_.id=?
User(id=1, userCode=admin, userName=系统管理员, userPassword=0000aaaa, gender=1, birthday=1983-10-10 00:00:00.0, phone=13688889999, address=北京市海淀区成府路207号, userRole=1, createdBy=1, creationDate=2013-03-21 16:52:07.0, modifyBy=null, modifyDate=null)

测试删除(简单和批量删除)

service层

java">    public void delete() {userRepository.deleteById(27);User user1 = userRepository.findById(28).get();User user2 = userRepository.findById(29).get();User user3 = userRepository.findById(30).get();List<User> users = new ArrayList<>(Arrays.asList(user1,user2,user3));userRepository.deleteInBatch(users);}

测试

java">    @Testvoid delete() {userService.delete();}

执行结果如下：

java">Hibernate: select user0_.id as id1_0_0_, user0_.address as address2_0_0_, user0_.birthday as birthday3_0_0_, user0_.createdBy as createdb4_0_0_, user0_.creationDate as creation5_0_0_, user0_.gender as gender6_0_0_, user0_.modifyBy as modifyby7_0_0_, user0_.modifyDate as modifyda8_0_0_, user0_.phone as phone9_0_0_, user0_.userCode as usercod10_0_0_, user0_.userName as usernam11_0_0_, user0_.userPassword as userpas12_0_0_, user0_.userRole as userrol13_0_0_ from smbms_user user0_ where user0_.id=?
Hibernate: delete from smbms_user where id=?
Hibernate: select user0_.id as id1_0_0_, user0_.address as address2_0_0_, user0_.birthday as birthday3_0_0_, user0_.createdBy as createdb4_0_0_, user0_.creationDate as creation5_0_0_, user0_.gender as gender6_0_0_, user0_.modifyBy as modifyby7_0_0_, user0_.modifyDate as modifyda8_0_0_, user0_.phone as phone9_0_0_, user0_.userCode as usercod10_0_0_, user0_.userName as usernam11_0_0_, user0_.userPassword as userpas12_0_0_, user0_.userRole as userrol13_0_0_ from smbms_user user0_ where user0_.id=?
Hibernate: select user0_.id as id1_0_0_, user0_.address as address2_0_0_, user0_.birthday as birthday3_0_0_, user0_.createdBy as createdb4_0_0_, user0_.creationDate as creation5_0_0_, user0_.gender as gender6_0_0_, user0_.modifyBy as modifyby7_0_0_, user0_.modifyDate as modifyda8_0_0_, user0_.phone as phone9_0_0_, user0_.userCode as usercod10_0_0_, user0_.userName as usernam11_0_0_, user0_.userPassword as userpas12_0_0_, user0_.userRole as userrol13_0_0_ from smbms_user user0_ where user0_.id=?
Hibernate: select user0_.id as id1_0_0_, user0_.address as address2_0_0_, user0_.birthday as birthday3_0_0_, user0_.createdBy as createdb4_0_0_, user0_.creationDate as creation5_0_0_, user0_.gender as gender6_0_0_, user0_.modifyBy as modifyby7_0_0_, user0_.modifyDate as modifyda8_0_0_, user0_.phone as phone9_0_0_, user0_.userCode as usercod10_0_0_, user0_.userName as usernam11_0_0_, user0_.userPassword as userpas12_0_0_, user0_.userRole as userrol13_0_0_ from smbms_user user0_ where user0_.id=?
Hibernate: delete from smbms_user where id=? or id=? or id=?

SpringData JPA的查询

第一种查询方式：约定方法名

• Spring Data JPA会根据前缀、中间连接词(Or、And、Like、NotNull等类似SQL中的关键词)，内部拼接SQL代理生成方法的实现。
• 约定方法名一定要符合命名规范

关键词	SQL符号	样例	对应JPQL 语句片段
And	and	findByLastnameAndFirstname	… where x.lastname = ?1 and x.firstname = ?2
Or	or	findByLastnameOrFirstname	… where x.lastname = ?1 or x.firstname = ?2
Is,Equals	=	findByFirstname,findByFirstnameIs,findByFirstnameEquals	… where x.firstname = ?1
Between	between xxx and xxx	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	is null	findByAgeIsNull	… where x.age is null
IsNotNull,NotNull	is not null	findByAge(Is)NotNull	… where x.age not null
Like	like	findByFirstnameLike	… where x.firstname like ?1
NotLike	not like	findByFirstnameNotLike	… where x.firstname not like ?1
StartingWith	like ‘xxx%’	findByFirstnameStartingWith	… where x.firstname like ?1(parameter bound with appended %)
EndingWith	like ‘xxx%’	findByFirstnameEndingWith	… where x.firstname like ?1(parameter bound with prepended %)
Containing	like ‘%xxx%’	findByFirstnameContaining	… where x.firstname like ?1(parameter bound wrapped in %)
OrderBy	order by	findByAgeOrderByLastnameDesc	… where x.age = ?1 order by x.lastname desc
Not	<>	findByLastnameNot	… where x.lastname <> ?1
In	in()	findByAgeIn(Collection ages)	… where x.age in ?1
NotIn	not in()	findByAgeNotIn(Collection ages)	… where x.age not in ?1
TRUE	=true	findByActiveTrue()	… where x.active = true
FALSE	=false	findByActiveFalse()	… where x.active = false
IgnoreCase	upper(xxx)=upper(yyyy)	findByFirstnameIgnoreCase	… where UPPER(x.firstame) = UPPER(?1)

示例

dao层

java">public interface UserRepository extends JpaRepository<User, Integer> {User findByUserCode(String userCode);
}

service层

java">    public Object findByUserCode(String userCode){return userRepository.findByUserCode(userCode);}

测试

java">    @Testvoid findByUserCode() {userService.findByUserCode("admin");}

执行结果如下：

java">Hibernate: select user0_.id as id1_0_, user0_.address as address2_0_, user0_.birthday as birthday3_0_, user0_.createdBy as createdb4_0_, user0_.creationDate as creation5_0_, user0_.gender as gender6_0_, user0_.modifyBy as modifyby7_0_, user0_.modifyDate as modifyda8_0_, user0_.phone as phone9_0_, user0_.userCode as usercod10_0_, user0_.userName as usernam11_0_, user0_.userPassword as userpas12_0_, user0_.userRole as userrol13_0_ from smbms_user user0_ where user0_.userCode=?

第二种查询方式：使用JPQL查询

• JPQL的全称为Java Persistence Query Language,是一种和SQL非常类似的中间性和对象化查询语言，它最终会被编译成针对不同底层数据库的SQL语言，从而屏蔽不同数据库之间的差异。
• JPQL和SQL很像,查询关键字都是一样的，唯一的区别是JPQL是面向对象的。
• JPQL里面不能出现表名,列名,只能出现Java的类名,属性名，并且区分大小写。不能使用select *。
• JPQL通过@Query注解，封装了执行数据库的查询的相关方法

示例

dao层

java">    @Query(value = "select u.userName from User u where u.userCode=?1")//@Query(value = "select u from User u where u.userCode=?1")String selByCode(String userCode);

service层

java">    public Object findByUserCode(String userCode){//return userRepository.findByUserCode(userCode);return userRepository.selByCode(userCode);}

测试执行结果如下：

java">Hibernate: select user0_.userName as col_0_0_ from smbms_user user0_ where user0_.userCode=?

第三种查询方式：使用Exampler查询

• 在 JpaRepository<T, ID>接口中定义了如下的方法
  • List findAll(Example var1);
  • List findAll(Example var1, Sort var2);
• Example接口，代表的是完整的查询条件。由实体对象（查询条件值）和匹配器（查询方式）共同创建。最终根据实例来findAll即可。
• 匹配器：ExampleMatcher对象，它是匹配“实体对象”的，表示了如何使用“实体对象”中的“值”进行查询，它代表的是“查询方式”，解释了如何去查的问题。
• 如：要查询姓“王”的客户，即姓名以“王”开头的客户，该对象就表示了“以某某开头的”这个查询方式。

示例

service层

java">    public List<User> getUser() {User user = new User();//user.setUserCode("zhanghua");user.setUserRole(3);user.setCreatedBy(2);Example<User> example = Example.of(user);return userRepository.findAll(example);}

测试

java">    @Testvoid getUser() {List<User> userList = userService.getUser();userList.forEach(System.out::println);}

执行结果如下:

java">Hibernate: select user0_.id as id1_0_, user0_.address as address2_0_, user0_.birthday as birthday3_0_, user0_.createdBy as createdb4_0_, user0_.creationDate as creation5_0_, user0_.gender as gender6_0_, user0_.modifyBy as modifyby7_0_, user0_.modifyDate as modifyda8_0_, user0_.phone as phone9_0_, user0_.userCode as usercod10_0_, user0_.userName as usernam11_0_, user0_.userPassword as userpas12_0_, user0_.userRole as userrol13_0_ from smbms_user user0_ where user0_.userRole=3 and user0_.createdBy=2
User(id=8, userCode=zhaoyan, userName=赵燕, userPassword=1, gender=1, birthday=1986-03-07 00:00:00.0, phone=18098764545, address=北京市海淀区回龙观小区10号楼, userRole=3, createdBy=2, creationDate=2016-04-21 13:54:07.0, modifyBy=null, modifyDate=null)
User(id=10, userCode=sunlei, userName=孙磊, userPassword=1, gender=2, birthday=1981-01-04 00:00:00.0, phone=13387676765, address=北京市朝阳区管庄新月小区12楼, userRole=3, createdBy=2, creationDate=2015-05-06 10:52:07.0, modifyBy=null, modifyDate=null)

第四种查询方式：使用原生SQL查询

• JPQL通过@Query注解，封装了执行数据库的查询的相关方法在

示例

dao层

java">    @Query(value = "select * from smbms_user where phone = :phone",nativeQuery = true)List<User> getUserByPhone(@Param("phone") String phone);

service层

java">    public  List<User> findUserByPhone() {return userRepository.getUserByPhone("13387676765");}

测试执行结果如下：

java">Hibernate: select * from smbms_user where phone = ?
User(id=10, userCode=sunlei, userName=孙磊, userPassword=1, gender=2, birthday=1981-01-04 00:00:00.0, phone=13387676765, address=北京市朝阳区管庄新月小区12楼, userRole=3, createdBy=2, creationDate=2015-05-06 10:52:07.0, modifyBy=null, modifyDate=null)

分页查询：

方式1：PagingAndSortingRepository分页接口，适用于简单的分页查询;

示例1

service层

java">    public Page<User> page(Integer currentPage) {User user = new User();//user.setUserCode("zhanghua");user.setUserRole(3);user.setCreatedBy(1);ExampleMatcher matcher = ExampleMatcher.matching().withIgnoreCase().withStringMatcher(ExampleMatcher.StringMatcher.CONTAINING);Example<User> example = Example.of(user,matcher);Pageable pageable = PageRequest.of(currentPage-1,5, Sort.by(Sort.Order.desc("birthday")));return userRepository.findAll(example,pageable);}

测试

java">    @Testvoid page() {Page<User> pageResult = userService.page(1);System.out.println(pageResult);}

执行结果如下：

java">Hibernate: select user0_.id as id1_0_, user0_.address as address2_0_, user0_.birthday as birthday3_0_, user0_.createdBy as createdb4_0_, user0_.creationDate as creation5_0_, user0_.gender as gender6_0_, user0_.modifyBy as modifyby7_0_, user0_.modifyDate as modifyda8_0_, user0_.phone as phone9_0_, user0_.userCode as usercod10_0_, user0_.userName as usernam11_0_, user0_.userPassword as userpas12_0_, user0_.userRole as userrol13_0_ from smbms_user user0_ where user0_.createdBy=1 and user0_.userRole=3 order by user0_.birthday desc limit ?
Page 1 of 1 containing cn.smbms.pojo.User instances

示例2：

dao层

java">    Page<User> findByUserCode(String userCode, Pageable pageable);

service层

java">    public Page<User> page(Integer currentPage) {Pageable pageable = PageRequest.of(currentPage-1,5, Sort.by(Sort.Order.desc("birthday")));return userRepository.findByUserCode("admin",pageable);}

方式2：Specification。自定义方法findAll，适用于动态分页查询；

• Specification 是Spring Data JPA提供的一种用于构建动态查询条件的接口，可以根据不同的条件动态组合查询条件,自定义的UserRepository 必须实现JpaSpecificationExecutor接口

示例

dao层

java">Page<SysUser> findAll(Specification<SysUser> specification,Pageable pageable);

service层

java">@Overridepublic Page<SysUser> findUserList(String userName, Integer userRole, Integer currentPageNo, Integer pageSize) throws Exception {Specification<SysUser> specification=new Specification<SysUser>() {@Overridepublic Predicate toPredicate(Root<SysUser> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {//断言List<Predicate> predicateList=new ArrayList<>();if(!StringUtils.isEmpty(userName)){Predicate predicate=criteriaBuilder.like(root.get("userName").as(String.class),"%"+userName+"%");predicateList.add(predicate);}if(!StringUtils.isEmpty(userRole) && userRole>0){Predicate predicate=criteriaBuilder.equal(root.get("userRole").as(Integer.class),userRole);predicateList.add(predicate);}return criteriaBuilder.and(predicateList.toArray(new Predicate[0]));}};Sort sort=Sort.by(Sort.Order.desc("id"));Pageable pageable=PageRequest.of(currentPageNo-1,pageSize,sort);return userRepository.findAll(specification,pageable);}

SpringData JPA配置多数据源

同源数据库的多源支持

日常项目中因为使用的分布式开发模式，不同的服务有不同的数据源，常常需要在一个项目中使用多个数据源，因此需要配置 Spring Boot Jpa 对多数据源的使用，一般分一下为三步：

1. 配置多数据源
2. 不同源的实体类放入不同包路径
3. 声明不同的包路径下使用不同的数据源、事务支持

异构数据库多源支持

比如我们的项目中，即需要对 mysql 的支持，也需要对 Mongodb 的查询等。实体类声明@Entity 关系型数据库支持类型，声明@Document 为 Mongodb 支持类型，不同的数据源使用不同的实体就可以了。

示例

java">interface PersonRepository extends Repository<Person, Long> {…
}@Entity
public class Person {…
}interface UserRepository extends Repository<User, Long> {…
}@Document
public class User {…
}

如果 User 用户既使用 Mysql 也使用 Mongodb也可以做混合使用

java">interface JpaPersonRepository extends Repository<Person, Long> {…
}interface MongoDBPersonRepository extends Repository<Person, Long> {…
}@Entity
@Document
public class Person {…
}

也可以通过对不同的包路径进行声明，比如 A 包路径下使用 mysql，B 包路径下使用 MongoDB。

java">@EnableJpaRepositories(basePackages = "com.neo.repositories.jpa")
@EnableMongoRepositories(basePackages = "com.neo.repositories.mongo")
interface Configuration { }

多数据源使用案例

1.依赖

略

2.配置

spring:datasource:smbms:driver-class-name: com.mysql.jdbc.Driverurl: jdbc:mysql://localhost:3306/smbms?useUnicode=true&characterEncoding=utf-8&useSSL=false&username: rootpassword: 123456news:driver-class-name: com.mysql.jdbc.Driverurl: jdbc:mysql://localhost:3306/news?useUnicode=true&characterEncoding=utf-8&useSSL=false&username: rootpassword: 123456jpa:show-sql: trueproperties:hibernate:hbm2ddl:auto: updatedialect: org.hibernate.dialect.MySQL5InnoDBDialectformat_sql: true

3.实体类

略

4.配置类

java">package cn.smbms.config;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateProperties;
import org.springframework.boot.autoconfigure.orm.jpa.HibernateSettings;
import org.springframework.boot.autoconfigure.orm.jpa.JpaProperties;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;import javax.annotation.Resource;
import javax.sql.DataSource;
import java.util.Map;/*** @author: zjl* @datetime: 2024/4/24* @desc:*/
@Configuration
public class DataSourceConfig {@Resourceprivate JpaProperties jpaProperties;@Resourceprivate HibernateProperties hibernateProperties;@Bean(name = "smbmsDataSource")@Primary@ConfigurationProperties("spring.datasource.smbms")public DataSource firstDataSource() {return DataSourceBuilder.create().build();}@Bean(name = "secondaryDataSource")@ConfigurationProperties("spring.datasource.secondary")public DataSource secondDataSource() {return DataSourceBuilder.create().build();}@Bean(name = "vendorProperties")public Map<String, Object> getVendorProperties() {return hibernateProperties.determineHibernateProperties(jpaProperties.getProperties(),new HibernateSettings());}
}

java">package cn.smbms.config;import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;import javax.annotation.Resource;
import javax.persistence.EntityManager;
import javax.sql.DataSource;
import java.util.Map;/*** @author: zjl* @datetime: 2024/4/24* @desc:*/
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(entityManagerFactoryRef = "entityManagerFactoryPrimary",transactionManagerRef = "transactionManagerPrimary",basePackages = {"cn.smbms.dao"})//设置dao（repo）所在位置
public class SmbmsConfig {@Resource(name = "smbmsDataSource")private DataSource dataSource;@Resource(name = "vendorProperties")private Map<String, Object> vendorProperties;@Bean(name = "entityManagerFactoryPrimary")@Primarypublic LocalContainerEntityManagerFactoryBean entityManagerFactoryPrimary(EntityManagerFactoryBuilder builder) {return builder.dataSource(dataSource).properties(vendorProperties).packages("cn.smbms.pojo") //设置实体类所在位置.persistenceUnit("primaryPersistenceUnit").build();}@Bean(name = "entityManagerPrimary")@Primarypublic EntityManager entityManager(EntityManagerFactoryBuilder builder) {return entityManagerFactoryPrimary(builder).getObject().createEntityManager();}@Bean(name = "transactionManagerPrimary")@PrimaryPlatformTransactionManager transactionManagerPrimary(EntityManagerFactoryBuilder builder) {return new JpaTransactionManager(entityManagerFactoryPrimary(builder).getObject());}}

java">package cn.smbms.config;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;import javax.persistence.EntityManager;
import javax.sql.DataSource;
import java.util.Map;/*** @author: zjl* @datetime: 2024/4/24* @desc:*/
@Configuration
@EnableTransactionManagement
@EnableJpaRepositories(entityManagerFactoryRef = "entityManagerFactorySecondary",transactionManagerRef = "transactionManagerSecondary",basePackages = {"cn.smbms.news.dao"})
public class NewsConfig {@Autowired@Qualifier("newsDataSource")private DataSource dataSource;@Autowired@Qualifier("vendorProperties")private Map<String, Object> vendorProperties;@Bean(name = "entityManagerFactorySecondary")public LocalContainerEntityManagerFactoryBean entityManagerFactorySecondary(EntityManagerFactoryBuilder builder) {return builder.dataSource(dataSource).properties(vendorProperties).packages("com.example.springbootmultijpa.model").persistenceUnit("secondaryPersistenceUnit").build();}@Bean(name = "entityManagerSecondary")public EntityManager entityManager(EntityManagerFactoryBuilder builder) {return entityManagerFactorySecondary(builder).getObject().createEntityManager();}@Bean(name = "transactionManagerSecondary")PlatformTransactionManager transactionManagerSecondary(EntityManagerFactoryBuilder builder) {return new JpaTransactionManager(entityManagerFactorySecondary(builder).getObject());}
}

5.业务逻辑层

略

6.测试

略