创建工程

1. 新建一个springboot工程
   
   目录结构如下
   

集成 hibernate

2. 在pom文件中导入相关依赖

   <!--数据库-->
   <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <scope>runtime</scope>
    </dependency>
    <!--jpa-->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>

3. 在 application.properties 添加 MySQL 配置 和 jpa 配置

# ============================== MySQL配置 =============================================================================
spring.datasource.url = jdbc:mysql://127.0.0.1:3306/hello?serverTimezone=GMT%2B8&useUnicode=true&characterEncoding=utf-8
spring.datasource.username = root
spring.datasource.password = root
spring.datasource.driverClassName = com.mysql.cj.jdbc.Driver

# =================================== JPA ===============================================================================
# Specify the DBMS
spring.jpa.database = MYSQL
# Show or not log for each sql query 是否打印 sql 语句
spring.jpa.show-sql = true
# Hibernate ddl auto (create, create-drop, update) 慎用 create ，因为create每次启动都会删除之前的表，再重新创建，数据会丢失
spring.jpa.hibernate.ddl-auto = update
# Naming strategy
spring.jpa.hibernate.naming-strategy = org.hibernate.cfg.DefaultNamingStrategy
# stripped before adding them to the entity manager 修改方言
#spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5Dialect
spring.jpa.properties.hibernate.dialect = org.hibernate.dialect.MySQL5InnoDBDialect

4. 创建工具类 Result

package com.example.demojpa.util;

public class Result {
    private int code = 200;
    private String msg = "操作成功";
    private Object data;

    public Result(int code,String msg){
        this.code = code;
        this.msg = msg;
    }

    public Result(Object data){
        this.data = data;
    }

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public Object getData() {
        return data;
    }

    public void setData(Object data) {
        this.data = data;
    }
}

5. 创建实体类 User

package com.example.demojpa.entity;

import javax.persistence.*;

/**
 * user 实体类
 */
@Entity
@Table(name = "t_user")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    Integer id;

    @Column(name = "name")
    String name;

    @Column(name = "age")
    int age;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

6. 创建服务层 UserService

package com.example.demojpa.service;

import com.example.demojpa.entity.User;
import com.example.demojpa.util.Result;

/**
 * 接口层:负责逻辑处理访问数据库层
 */
public interface UserService {
    /**
     * 保存 user 对象
     * @param user
     * @return
     */
    Result saveUser(User user);

    /**
     * 查询所有user
     * @return
     */
    Result queryAll();

    /**
     * 通过name和age查询
     * @param name
     * @param age
     * @return
     */
    Result getByNameAndAge(String name,int age);
}

7. 创建实现类 UserServiceImpl

package com.example.demojpa.service.impl;

import com.example.demojpa.dao.UserRepository;
import com.example.demojpa.entity.User;
import com.example.demojpa.service.UserService;
import com.example.demojpa.util.Result;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.util.List;

/**
 * 实现接口的抽象方法
 */
@Service
public class UserServiceImpl implements UserService {
    @Resource
    UserRepository userRepository;

    @Override
    public Result saveUser(User user) {
        User save = userRepository.save(user);
        return new Result(save);
    }

    @Override
    public Result queryAll() {
        List <User> list = userRepository.findAll();
        return new Result(list);
    }

    @Override
    public Result getByNameAndAge(String name, int age) {
        List <User> list = userRepository.getByNameAndAge(name, age);
        return new Result(list);
    }
}

8. 创建 UserRepository 数据访问接口

package com.example.demojpa.dao;

import com.example.demojpa.entity.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import java.util.List;

/**
 * 继承JpaRepository<User,Integer>
 *     User：要操作的表格对象
 *     Integer：主键 ID 的数据类型
 *
 *     继承的这个类里面封装了基本的增删改查方法直接调用即可，
 *     如果集成的方法没法满足需求，可以在此封装,但是一定要注意 “命名规范”
 */
@Repository(value = "userRepository")
public interface UserRepository extends JpaRepository<User,Integer> {
    List<User> getByNameAndAge(String name,int age);
}

9. 创建 controller 控制器 UserController

package com.example.demojpa.controller;

import com.example.demojpa.entity.User;
import com.example.demojpa.service.UserService;
import com.example.demojpa.util.Result;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserController {
    @Autowired
    UserService userService;

    /**
     * 保存user
     * @param user
     * @return
     */
    @PostMapping("/saveUser")
    public Result saveUser(@RequestBody User user){
        return userService.saveUser(user);
    }

    /**
     * 查询所有user
     * @return
     */
    @GetMapping("/queryAll")
    public Result queryAll(){
        return userService.queryAll();
    }

    /**
     * 通过name和age查询
     * @param name
     * @param age
     * @return
     */
    @GetMapping("/getByNameAndAge")
    public Result getByNameAndAge(String name,int age){
        return userService.getByNameAndAge(name,age);
    }
}

10. 最后直接使用postman测试一下就好了，在这就不贴效果了，总的目录结构
    

总结

hibernate配置默认会自动创建表格，但是不是创建数据库，如果自动创建表失败，可能是方言设置有问题，ddl-auto = update有几种值，(create, create-drop, update)，create相关的慎用，因为每次启动都会清空表。还有一定要注意 hibernate 命名规范。