一、Spring Data简介
项目的目的是为了简化构建基于 Spring 框架应用的数据访问技术，包括非关系数据库、
Map-Reduce 框架、云数据服务等等；另外也包含对关系数据库的访问支持。
SpringData为我们提供使用统一的API来对数据访问层进行操作：
Repository<T, ID extends Serializable>：统一接口
RevisionRepository<T, ID extends Serializable, N extends Number & Comparable<N>>：基于乐观
锁机制
CrudRepository<T, ID extends Serializable>：基本CRUD操作
PagingAndSortingRepository<T, ID extends Serializable>：基本CRUD及分页
二、JPA整合示例
工程目录
引入依赖： spring-boot-starter-data-jpa
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
1）编写一个实体类（bean）和数据表进行映射，并且配置好映射关系
Entity
Employee类
package com.example.demo.entity;
import java.util.Date;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.Table;
//使用JPA注解配置映射关系
@Entity //告诉JPA这是一个实体类（和数据表映射的类）
@Table(name = "t_employee") //@Table来指定和哪个数据表对应;如果省略默认表名就是user；
public class Employee {
@Id //这是一个主键
@GeneratedValue(strategy = GenerationType.IDENTITY)//自增主键
private Integer id;
@Column(name = "last_name",length = 30) //这是和数据表对应的一个列
private String lastName;
@Column(name = "email")
private String email;
//1 male, 0 female
@Column(name = "gender")
private Integer gender;
@ManyToOne(targetEntity=Department.class,cascade=CascadeType.ALL,optional=true)
@JoinColumn(name="department_id",nullable=true)
private Department department;
@Column(name = "birth")
private Date birth;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public Integer getGender() {
return gender;
}
public void setGender(Integer gender) {
this.gender = gender;
}
public Department getDepartment() {
return department;
}
public void setDepartment(Department department) {
this.department = department;
}
public Date getBirth() {
return birth;
}
public void setBirth(Date birth) {
this.birth = birth;
}
public Employee(Integer id, String lastName, String email, Integer gender,
Department department, Date birth) {
super();
this.id = id;
this.lastName = lastName;
this.email = email;
this.gender = gender;
this.department = department;
this.birth = birth;
}
public Employee() {
super();
// TODO Auto-generated constructor stub
}
@Override
public String toString() {
return "Employee [id=" + id + ", lastName=" + lastName + ", email="
+ email + ", gender=" + gender + ", department=" + department
+ ", birth=" + birth + "]";
}
}
Department类
package com.example.demo.entity;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity //告诉JPA这是一个实体类（和数据表映射的类）
@Table(name = "t_department")
public class Department {
@Id //这是一个主键
@GeneratedValue(strategy = GenerationType.IDENTITY)//自增主键
private Integer id;
@Column(name = "department_name",length = 50) //这是和数据表对应的一个列
private String departmentName;
@OneToMany(mappedBy="department",cascade=CascadeType.ALL)
private Set<Employee> emps ;
public Department() {
}
public Department(int i, String string) {
this.id = i;
this.departmentName = string;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getDepartmentName() {
return departmentName;
}
public void setDepartmentName(String departmentName) {
this.departmentName = departmentName;
}
public Set<Employee> getEmps() {
return emps;
}
public void setEmps(Set<Employee> emps) {
this.emps = emps;
}
@Override
public String toString() {
return "Department [id=" + id + ", departmentName=" + departmentName + "]";
}
}
多表联查的重点是：@ManyToOne@JoinColumn@OneToMany注解的使用
2）编写一个Dao接口来操作实体类对应的数据表（Repository）
repository层
EmployeeRepository
package com.example.demo.repository;
import org.springframework.data.domain.Example;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.jpa.repository.JpaRepository;
import com.example.demo.entity.Employee;
public interface EmployeeRepository extends JpaRepository<Employee,Integer>{
@Override
public <S extends Employee> Page<S> findAll(Example<S> example,
Pageable pageable);
}
3）基本的配置JpaProperties
spring.jpa.show-sql=true
Service 层
package com.example.demo.service;
import org.springframework.data.domain.Page;
import com.example.demo.entity.Employee;
public interface EmployeeService {
public Page<Employee> findAll(String lastName , Integer gender , Integer deptId,Integer pageNumber,Integer pageSize);
}
ServiceImpl 层
package com.example.demo.service.impl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Example;
import org.springframework.data.domain.ExampleMatcher;
import org.springframework.data.domain.ExampleMatcher.GenericPropertyMatchers;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.stereotype.Service;
import org.springframework.util.StringUtils;
import com.example.demo.entity.Department;
import com.example.demo.entity.Employee;
import com.example.demo.repository.EmployeeRepository;
import com.example.demo.service.EmployeeService;
@Service
public class EmployeeServiceImpl implements EmployeeService {
@Autowired
private EmployeeRepository employeeRepository;
@Override
public Page<Employee> findAll(String lastName , Integer gender , Integer deptId ,Integer pageNumber,Integer pageSize) {
Employee emp =new Employee();
if (!StringUtils.isEmpty(lastName)) {
emp.setLastName(lastName);
}
if (gender != null){
emp.setGender(gender);
}
if (deptId != null){
emp.setDepartment(new Department(deptId,null));
}
ExampleMatcher matcher = ExampleMatcher.matching();
if (!StringUtils.isEmpty(lastName)) {
matcher.withMatcher("lastName", GenericPropertyMatchers.contains());
}
if (gender != null){
matcher.withMatcher("gender", GenericPropertyMatchers.exact());
}
if (deptId != null){
matcher.withMatcher("department.id", GenericPropertyMatchers.exact());
}
Example<Employee> ex = Example.of(emp, matcher);
Pageable pageable = new PageRequest(pageNumber,pageSize,Sort.Direction.ASC,"id");
return employeeRepository.findAll(ex, pageable);
}
}
由于对Spring Data JPA 应用进行深入研究，此处就只是简单实现了JPA 的分页功能。
测试
package com.example.demo;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.data.domain.Page;
import org.springframework.test.context.junit4.SpringRunner;
import com.example.demo.entity.Employee;
import com.example.demo.repository.EmployeeRepository;
import com.example.demo.service.EmployeeService;
@RunWith(SpringRunner.class)
@SpringBootTest
public class SpringBoot02ApplicationTests {
@Autowired
EmployeeRepository empRepository;
@Autowired
EmployeeService employeeService;
@Test
public void contextLoads() {
Page<Employee> page = employeeService.findAll(null, null, 2, 0, 2);
System.out.println(page.getContent());
System.out.println(page.getSize());
System.out.println(page.getTotalPages());
}
}
参考：https://blog.csdn.net/qq_34083066/article/details/80733512
http://www.luckyzz.com/java/spring-data-jpa/
原文地址：https://www.cnblogs.com/xiaoliangup/p/10420595.html
时间： 2024-10-01 05:24:30