使用IDEA开发 Springdata-jpa
1.首先创建一个Spring Boot项目
2、配置yml文件
application.yml
spring:
datasource:
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
username: root
password: root
jpa:
show-sql: true #显示sql语句
hibernate:
ddl-auto: update
naming:
implicit-strategy: org.hibernate.boot.model.naming.ImplicitNamingStrategyComponentPathImpl
physical-strategy: org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl
database: mysql #配置现在所使用的数据库
3、添加实体类
@Data 自动封装属性
@Entity注解用于生成数据库表,
@Table用于指定表的名称,
@GeneratedValue用于根据规则生成主键,
@Id表示这是一个主键。(还有一些标签可以自己去看一下springdata-jpa的官方文档)
Spring Data Jpa 可以根据实体类 在数据库里自动生成表(注意:yml数据里面首先需要一个数据库,然后必须连接)
package com.haungyu.springbootjpa.entity;
import lombok.Data;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
/**
* @date :2019/6/3 21:39
* 学生类
*/
@Data
@Entity
@Table(name = "student")
public class Student {
@Id
private Long id;
private String name;
private String sex;
private Integer gradeId;
}
package com.haungyu.springbootjpa.entity;
import lombok.Data;
import javax.persistence.*;
/**
* @date :2019/6/3 21:42
* 年级表
*/
@Data
@Entity
@Table(name = "grade")
public class Grade {
@Id//主键
@GeneratedValue(strategy = GenerationType.IDENTITY)//自动增长
private Integer gradeId;
private String gradeName
}
建好实体类后,启动项目
然后编写Dao层接口
DAO的接口:
Repository (空接口)
CrudRepository (增删改查)
PagingAndSortingRepository (分页和排序)
JpaRepository (扩展增删改查、批量操作)
JpaSpecificationExecutor:用来做负责查询的接口
Specification:是Spring Data JPA提供的一个查询规范,要做复杂的查询,类似hibernate QBC查询
JpaRepository继承PagingAndSortingRepository,CrudRepository:
CrudRepository 提供 save、 delete、 deteleAll、 findAll、 findOne、 count等方法
PagingAndSortingRepository提供排序及分页findAll(Sort) (基于排序的查询)、findAll(Pageable)( 基于分页的查询)
编写Service层
因为id我没有给自增 所以要手动给id并且不能重复
先创建工具类(util)
package com.huipeng.springbootjpa.util;
import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
/**
* <p>名称:IdWorker.java</p>
* <p>描述:分布式自增长ID</p>
* <pre>
* Twitter的 Snowflake JAVA实现方案
* </pre>
* 核心代码为其IdWorker这个类实现,其原理结构如下,我分别用一个0表示一位,用—分割开部分的作用:
* 1||0---0000000000 0000000000 0000000000 0000000000 0 --- 00000 ---00000 ---000000000000
* 在上面的字符串中,第一位为未使用(实际上也可作为long的符号位),接下来的41位为毫秒级时间,
* 然后5位datacenter标识位,5位机器ID(并不算标识符,实际是为线程标识),
* 然后12位该毫秒内的当前毫秒内的计数,加起来刚好64位,为一个Long型。
* 这样的好处是,整体上按照时间自增排序,并且整个分布式系统内不会产生ID碰撞(由datacenter和机器ID作区分),
* 并且效率较高,经测试,snowflake每秒能够产生26万ID左右,完全满足需要。
* <p>
* 64位ID (42(毫秒)+5(机器ID)+5(业务编码)+12(重复累加))
*
* @author Polim
*/
public class IdWorker {
// 时间起始标记点,作为基准,一般取系统的最近时间(一旦确定不能变动)
private final static long twepoch = 1288834974657L;
// 机器标识位数
private final static long workerIdBits = 5L;
// 数据中心标识位数
private final static long datacenterIdBits = 5L;
// 机器ID最大值
private final static long maxWorkerId = -1L ^ (-1L << workerIdBits);
// 数据中心ID最大值
private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
// 毫秒内自增位
private final static long sequenceBits = 12L;
// 机器ID偏左移12位
private final static long workerIdShift = sequenceBits;
// 数据中心ID左移17位
private final static long datacenterIdShift = sequenceBits + workerIdBits;
// 时间毫秒左移22位
private final static long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
private final static long sequenceMask = -1L ^ (-1L << sequenceBits);
/* 上次生产id时间戳 */
private static long lastTimestamp = -1L;
// 0,并发控制
private long sequence = 0L;
private final long workerId;
// 数据标识id部分
private final long datacenterId;
public IdWorker(){
this.datacenterId = getDatacenterId(maxDatacenterId);
this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
}
/**
* @param workerId
* 工作机器ID
* @param datacenterId
* 序列号
*/
public IdWorker(long workerId, long datacenterId) {
if (workerId > maxWorkerId || workerId < 0) {
throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
}
if (datacenterId > maxDatacenterId || datacenterId < 0) {
throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
}
this.workerId = workerId;
this.datacenterId = datacenterId;
}
/**
* 获取下一个ID
*
* @return
*/
public synchronized long nextId() {
long timestamp = timeGen();
if (timestamp < lastTimestamp) {
throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
}
if (lastTimestamp == timestamp) {
// 当前毫秒内,则+1
sequence = (sequence + 1) & sequenceMask;
if (sequence == 0) {
// 当前毫秒内计数满了,则等待下一秒
timestamp = tilNextMillis(lastTimestamp);
}
} else {
sequence = 0L;
}
lastTimestamp = timestamp;
// ID偏移组合生成最终的ID,并返回ID
long nextId = ((timestamp - twepoch) << timestampLeftShift)
| (datacenterId << datacenterIdShift)
| (workerId << workerIdShift) | sequence;
return nextId;
}
private long tilNextMillis(final long lastTimestamp) {
long timestamp = this.timeGen();
while (timestamp <= lastTimestamp) {
timestamp = this.timeGen();
}
return timestamp;
}
private long timeGen() {
return System.currentTimeMillis();
}
/**
* <p>
* 获取 maxWorkerId
* </p>
*/
protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
StringBuffer mpid = new StringBuffer();
mpid.append(datacenterId);
String name = ManagementFactory.getRuntimeMXBean().getName();
if (!name.isEmpty()) {
/*
* GET jvmPid
*/
mpid.append(name.split("@")[0]);
}
/*
* MAC + PID 的 hashcode 获取16个低位
*/
return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
}
/**
* <p>
* 数据标识id部分
* </p>
*/
protected static long getDatacenterId(long maxDatacenterId) {
long id = 0L;
try {
InetAddress ip = InetAddress.getLocalHost();
NetworkInterface network = NetworkInterface.getByInetAddress(ip);
if (network == null) {
id = 1L;
} else {
byte[] mac = network.getHardwareAddress();
id = ((0x000000FF & (long) mac[mac.length - 1])
| (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
id = id % (maxDatacenterId + 1);
}
} catch (Exception e) {
System.out.println(" getDatacenterId: " + e.getMessage());
}
return id;
}
}
package com.huipeng.springbootjpa.service;
import com.haungyu.springbootjpa.entity.Student;
import java.util.List;
/**
* @date :2019/6/3 22:11
*
*/
public interface StudnetService {
/** 查询所有 */
List<Student> findAll();
/** 新增和修改 */
void save(Student student);
/** 删除 */
void delete(Long id);
/**查询单个对象 */
Student findById(Long id);
}
package com.huipeng.springbootjpa.service.impl;
import com.haungyu.springbootjpa.dao.StudentDao;
import com.haungyu.springbootjpa.entity.Student;
import com.haungyu.springbootjpa.service.StudnetService;
import com.haungyu.springbootjpa.util.IdWorker;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
/**
* @date :2019/6/3 22:16
*/
@Service
public class StudnetServiceImpl implements StudnetService {
@Autowired
private StudentDao stu;
IdWorker idWorker = new IdWorker();
@Override
public List<Student> findAll() {
return stu.findAll();
}
@Override
public void save(Student student) {
//当 对象的id为空时,新增一个id,不为空时 修改信息
if (student.getId()==null){
//添加 id
student.setId(idWorker.nextId());
}
stu.save(student);
}
@Override
public void delete(Long id) {
//根据id删除信息
stu.deleteById(id);
}
@Override
public Student findById(Long id) {
return stu.findById(id).get();
}
}
编写Controller 控制层
package com.huipeng.springbootjpa.controller;
import com.haungyu.springbootjpa.entity.Student;
import com.haungyu.springbootjpa.service.StudnetService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import java.util.List;
/**
* @date :2019/6/3 22:23
* 学生类的控制层
*/
@Controller
public class StudentController {
@Autowired
private StudnetService stu;
@RequestMapping("/index")
public String findAll(Model model){
//查询所有
List<Student> list = stu.findAll();
model.addAttribute("list",list);
return "index";
}
@RequestMapping("/updateById/{id}")
public String updateById(@PathVariable("id") Long id,Model model){
System.out.println("============"+id);
if (id!=0){
//根据id查询对象
Student student = stu.findById(id);
model.addAttribute("stu",student);
}
return "update";
}
/**
* @Description //TODO 删除
* @Date 16:26 2019/6/3
* @Param
* @return
**/
@RequestMapping("/delete/{id}")
public String delete(@PathVariable("id") Long id){
stu.delete(id);
return "redirect:/index";
}
/**
* @Author 甘环宇
* @Description //TODO 新增,修改
* @Date 18:21 2019/6/3
* @Param
* @return
**/
@RequestMapping("/update")
public String update(Student student){
stu.save(student);
return "redirect:/index";
}
}
编写html 页面
<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<form action="">
<a th:href="@{'/updateById/0'}">新增学生</a>
<table cellpadding="10" cellspacing="0" border="1">
<tr>
<th>学生编号</th>
<th>学生姓名</th>
<th>学生性别</th>
<th>学生班级</th>
<th>操作</th>
</tr>
<tr th:each="li:${list}">
<td th:text="${li.id}"></td>
<td th:text="${li.name}">1</td>
<td th:text="${li.sex}">1</td>
<td th:text="${li.gradeId}">1</td>
<td><a th:href="@{'/delete/'+${li.id}}">删除</a></td>
<td><a th:href="@{'/updateById/'+${li.id}}">修改</a></td>
</tr>
</table>
</form>
</body>
</html>
<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<form action="/update">
<input type="hidden" name="id" th:value="${stu!=null}?${stu.id}">
姓名:<input type="text" name="name" th:value="${stu!=null}?${stu.name}"><br/>
性别:<input type="text" name="sex" th:value="${stu!=null}?${stu.sex}"><br/>
班级:<select name="gradeId">
<option value="1">S1</option>
<option value="2">S2</option>
<option value="3">Y2</option>
</select><br/>
<input type="submit" th:value="${stu!=null}?修改:新增">
</form>
</body>
</html>