SpringData入门(四)-Spring data JPA高级

• 今天要讲的这几个接口都是Repository接口的子接口
  

一.CrudRepository接口使用详解

• save(entity)：保存一个实体

• save(entities)：保存多个实体

• findOne(id)：找到一个对象

• exists(id)：根据ID判断对象是否存在

• findAll()：找到所有实体对象

• delete(id)：根据ID删除实体对象

• delete(entity)：根据实体对象删除实体对象

• delete(entities)：删除多个实体对象

• deleteAll()：删除所有实体对象

• 为了避免和前面章节的表起冲突，我们换一个表名
  

• 继承CrudRepository接口

public interface EmployeeCrudRepository extends CrudRepository<Employee,Integer> {


}

• 测试类

public class EmployeeCrudReositoryTest {


    private ApplicationContext ctx = null;

    private EmployeeCrudRepository employeeCrudRepository;
    @Before
    public void init(){
         ctx = new AnnotationConfigApplicationContext(SpringConfigNew.class);
         employeeCrudRepository = ctx.getBean(EmployeeCrudRepository.class);
    }

    @After
    public void destroy(){
         ctx = null;
    }

    @Test
    public void saveTest(){
        List<Employee> employees = new ArrayList<>();
        for(int i=0;i<100;i++){

            Employee employee = new Employee();

            employee.setName("test"+i);
            employee.setAge(100-i);

            employees.add(employee);
        }
        employeeCrudRepository.saveAll(employees);

    }
}

• 存入100个数据
  

二.PagingAndSortingRespository接口使用详解

• 该接口包含分页和排序的功能
• 带排序的查询：findAll(Sort sort)
• 带排序的分页查询：findAll(Pageable pageable)
• 继承PagingAndSortingRespository接口

public interface EmployeePagingAndSortingRepository extends PagingAndSortingRepository<Employee,Integer> {

}

• 测试类

public class EmployeePagingAndSortingRepositoryTest {

    private ApplicationContext ctx = null;

    private EmployeePagingAndSortingRepository employeePagingAndSortingRepository;
    @Before
    public void init(){
        ctx = new AnnotationConfigApplicationContext(SpringConfigNew.class);
        employeePagingAndSortingRepository = ctx.getBean( EmployeePagingAndSortingRepository.class);
    }

    @After
    public void destroy(){
        ctx = null;
    }

    //分页测试
    @Test
    public void PageTest(){

        //Pageable pageable = new PageRequest(0,9); 方法过期，现在直接用静态方法了
        //index是从0开始的，不是从1开始的
        Pageable pageable = PageRequest.of(1,9);//page是从0开始的 一页9个记录
        Page<Employee> employeePage = employeePagingAndSortingRepository.findAll(pageable);

        System.out.println("查询的总页数:"+employeePage.getTotalPages());
        System.out.println("查询的总记录数:"+employeePage.getTotalElements());
        System.out.println("查询的当前第几页:"+employeePage.getNumber()+1);
        System.out.println("查询的当前页面的集合:"+employeePage.getContent());
        System.out.println("查询的当前页面的记录数:"+employeePage.getNumberOfElements());


    }

    //排序和分页测试
    @Test
    public void PageAndSort(){
        Sort.Order order = new Sort.Order(Sort.Direction.ASC,"id");//以id升序

        //Sort sort = new Sort(order); 过期了 也是静态方法
        Sort sort = Sort.by(order);

        //Pageable pageable = new PageRequest(0,9, sort); 过期了 也是静态方法
        Pageable pageable = PageRequest.of(0,9,sort);

        Page<Employee> employeePage = employeePagingAndSortingRepository.findAll(pageable);

        System.out.println("查询的总页数:"+employeePage.getTotalPages());
        System.out.println("查询的总记录数:"+employeePage.getTotalElements());
        System.out.println("查询的当前第几页:"+employeePage.getNumber()+1);
        System.out.println("查询的当前页面的集合:"+employeePage.getContent());
        System.out.println("查询的当前页面的记录数:"+employeePage.getNumberOfElements());
    }
}

三.JpaRepository接口使用详解

• finaAll：查询所有记录
• findAll(Sort sort)：查询所有记录并排序
• save(entities)：保存多个实体对象
• flush：
• deleteInBatch(entities)：一个批次里面删除那些实体
• 继承JpaRepository接口

public interface EmployeeJpaRepository extends JpaRepository<Employee,Integer> {
}

• 测试类

public class EmployeeJpaRepositoryTest {

    private ApplicationContext ctx = null;

    private EmployeeJpaRepository employeeJpaRepository;
    @Before
    public void init(){
        ctx = new AnnotationConfigApplicationContext(SpringConfigNew.class);
        employeeJpaRepository = ctx.getBean(EmployeeJpaRepository.class);
    }

    @After
    public void destroy(){
        ctx = null;
    }

    @Test
    public void findTest(){
        Employee employee = employeeJpaRepository.findById(99).get();
        System.out.println("employee:"+ employee.toString());

        System.out.println("employee(88)"+employeeJpaRepository.existsById(88));
        System.out.println("employee(101)"+employeeJpaRepository.existsById(101));

    }
}

四.JpaSpecificationExecutor接口使用详解

• 这个不属于之前介绍的结构体系 是单独的，Specification封装了JPA Criteria查询条件
• 继承JpaSpecificationExecutor接口

//接口可以多继承 多继承 功能更加强大
public interface EmployeeJpaSpecificationExecutor extends  JpaRepository<Employee,Integer>,JpaSpecificationExecutor<Employee> {
}

• 测试类

public class EmployeeJpaSpecificationExecutorTest {
    private ApplicationContext ctx = null;

    private EmployeeJpaSpecificationExecutor employeeJpaSpecificationExecutor = null;
    @Before
    public void init(){
        ctx = new AnnotationConfigApplicationContext(SpringConfigNew.class);
        employeeJpaSpecificationExecutor = ctx.getBean(EmployeeJpaSpecificationExecutor.class);
    }

    @After
    public void destroy(){
        ctx = null;
    }

    /*
    1.分页
    2.排序
    3.查询条件:age > 50
     */
    @Test
    public void queryTest(){

        Sort.Order order = new Sort.Order(Sort.Direction.ASC,"id");

        Sort sort = Sort.by(order);

        Pageable pageable = PageRequest.of(0,9,sort);

        /*
        root:查询的类型
        query : 添加查询条件
        cb : 构建 Predicate
         */
        Specification<Employee> specification = new Specification<Employee>() {
            //查询条件
            @Override
            public Predicate toPredicate(Root<Employee> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
                //root(employee(age))
                Path path = root.get("age");
                return cb.gt(path,50);
            }
        };

        Page<Employee> employeePage = employeeJpaSpecificationExecutor.findAll(specification,pageable);

        System.out.println("查询的总页数:"+employeePage.getTotalPages());
        System.out.println("查询的总记录数:"+employeePage.getTotalElements());
        System.out.println("查询的当前第几页:"+employeePage.getNumber()+1);
        System.out.println("查询的当前页面的集合:"+employeePage.getContent());
        System.out.println("查询的当前页面的记录数:"+employeePage.getNumberOfElements());

    }

}