SpringDataJPA（四）多条件查询接口JpaSpecificationExecutor的使用

源码

GitHub： https://github.com/291685399/springboot-learning/tree/master/springboot-springdatajpa04

JpaSpecificationExecutor接口

• JpaSpecificationExecutor接口是单独存在的，完全独立的
• 该接口主要是提供了多条件查询的支持，并且可以在查询中添加分页与排序
• 该接口需要配合其他接口（例如Repository、CurdRepository、JPARepository、PagingAndSortingRepositor）进行使用，要不然注入实现接口对象的时候会报错，在IOC容器中不能找到该bean

JpaSpecificationExecutor接口中声明了五个方法，下面将介绍这五个方法的使用

public interface JpaSpecificationExecutor<T> {

    Optional<T> findOne(@Nullable Specification<T> var1);

    List<T> findAll(@Nullable Specification<T> var1);

    Page<T> findAll(@Nullable Specification<T> var1, Pageable var2);

    List<T> findAll(@Nullable Specification<T> var1, Sort var2);

    long count(@Nullable Specification<T> var1);
}

使用JpaSpecificationExecutor接口

pom.xml：

<dependencies>
    
    <dependency>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-webartifactId>
    dependency>
    <dependency>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-testartifactId>
        <scope>testscope>
    dependency>

    
    **<dependency>
        <groupId>org.springframework.bootgroupId>
        <artifactId>spring-boot-starter-data-jpaartifactId>
    dependency>**

    
    <dependency>
        <groupId>mysqlgroupId>
        <artifactId>mysql-connector-javaartifactId>
        <scope>runtimescope>
    dependency>

    
    <dependency>
        <groupId>org.projectlombokgroupId>
        <artifactId>lombokartifactId>
        <optional>trueoptional>
    dependency>
dependencies>

application.properties：

# datasource
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/springboot-springdatajpa04?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&useSSL=true
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=root
# springdatajpa
#打印出自动生产的SQL，方便调试的时候查看
spring.jpa.show-sql=true
#更新数据库表结构
spring.jpa.hibernate.ddl-auto=update
#对打印的sql进行格式化，方便查看
spring.jpa.properties.hibernate.format_sql=true
spring.jpa.properties.hibernate.use_sql_comments=true
#指定生成表名的存储引擎为InneoDB
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialect

User：

@Entity
@Data
@Table(name = "user")
public class User implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private int id;
    private String name;
    private Integer age;
    private String sex;
    private String address;
    private String phone;
}

UserJPASpecificationExecutor：

public interface UserJPASpecificationExecutor extends JpaRepository<User, Integer>, JpaSpecificationExecutor<User> {
}

UserRepositoryTests：

@RunWith(SpringRunner.class)
@SpringBootTest
public class UserJPASpecificationExecutorTests {

    @Autowired
    private UserJPASpecificationExecutor userJPASpecificationExecutor;

    /**
     * findOne
     */
    @Test
    public void findAllTest1() {
        Specification<User> specification = new Specification<User>() {
            @Override
            public Predicate toPredicate(Root<User> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
                //select * from user where phone='12345697842'
                return criteriaBuilder.equal(root.get("phone"), "12345697842");
            }
        };
        Optional<User> userOptional = userJPASpecificationExecutor.findOne(specification);
        User user = userOptional.get();
        System.out.println(user);
    }

    /**
     * List findAll(@Nullable Specification var1);
     */
    @Test
    public void findAllTest2_1() {
        /**
         * Specification：用于封装查询条件
         */
        Specification<User> specification = new Specification<User>() {
            /**
             * Predicate：封装单个查询条件
             * @param root：查询对象的属性封装，或者说是User的包装类
             * @param criteriaQuery：封装了要执行的查询中的各个部分的信息，select、from、order by
             * @param criteriaBuilder：查询条件的构造器，定义不同的查询条件
             * @return
             */
            @Override
            public Predicate toPredicate(Root<User> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
                //select * from user where name='张三'
                Predicate predicate = criteriaBuilder.equal(root.get("name"), "张三");
                return predicate;
            }
        };
        List<User> userList = userJPASpecificationExecutor.findAll(specification);
        System.out.println(userList);
    }

    /**
     * List findAll(@Nullable Specification var1);
     */
    @Test
    public void findAllTest2_2() {
        Specification<User> specification = new Specification<User>() {
            @Override
            public Predicate toPredicate(Root<User> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
                //select * from user where name='张三' and age ='34'
                List<Predicate> predicateList = new ArrayList<>();
                predicateList.add(criteriaBuilder.equal(root.get("name"), "张三"));
                predicateList.add(criteriaBuilder.equal(root.get("age"), 34));
                Predicate[] predicates = new Predicate[predicateList.size()];
                return criteriaBuilder.and(predicateList.toArray(predicates));
                //或者使用：return criteriaBuilder.and(criteriaBuilder.equal(root.get("name"), "张三"),criteriaBuilder.equal(root.get("age"), 34));
            }
        };
        List<User> userList = userJPASpecificationExecutor.findAll(specification);
        System.out.println(userList);
    }

    /**
     * Page findAll(@Nullable Specification var1, Pageable var2);
     */
    @Test
    public void findAllTest3() {
        Specification<User> specification = new Specification<User>() {
            @Override
            public Predicate toPredicate(Root<User> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
                //select * from user where name='张三' and age ='34'
                return criteriaBuilder.and(criteriaBuilder.equal(root.get("name"), "张三"), criteriaBuilder.equal(root.get("age"), 34));
            }
        };
        //order by id desc limit 0,1
        PageRequest pageRequest=new PageRequest(0,1,new Sort(Sort.Direction.DESC,"id"));
        Page<User> userPage = userJPASpecificationExecutor.findAll(specification, pageRequest);
        List<User> userList = userPage.getContent();
        System.out.println(userList);
    }

    /**
     * List findAll(@Nullable Specification var1, Sort var2);
     */
    @Test
    public void findAllTest4() {
        Specification<User> specification = new Specification<User>() {
            @Override
            public Predicate toPredicate(Root<User> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
                //select * from user where name='张三' and age ='34'
                return criteriaBuilder.and(criteriaBuilder.equal(root.get("name"), "张三"), criteriaBuilder.equal(root.get("age"), 34));
            }
        };
        //order by id desc
        Sort sort = new Sort(new Sort.Order(Sort.Direction.DESC, "id"));
        List<User> userList = userJPASpecificationExecutor.findAll(specification, sort);
        System.out.println(userList);
    }

    /**
     * long count(@Nullable Specification var1);
     */
    @Test
    public void findAllTest5() {
        Specification<User> specification = new Specification<User>() {
            @Override
            public Predicate toPredicate(Root<User> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder criteriaBuilder) {
                //select * from user where name='张三'
                return criteriaBuilder.equal(root.get("name"), "张三");
            }
        };
        long count = userJPASpecificationExecutor.count(specification);
        System.out.println(count);
    }
}