spring boot学习(4) SpringBoot 之Spring Data Jpa 支持（1）

时间：2023-11-17 19:43:02
第一节：Spring Data Jpa 简介

Spring-Data-Jpa

JPA(Java Persistence API)定义了一系列对象持久化的标准，目前实现这一规范的产品有Hibernate、TopLink等。

第二节：Spring Data Jpa 基本crud 实现
下面对图书的CRUD来为例子：
项目结构：
spring boot学习(4) SpringBoot 之Spring Data Jpa 支持（1）
1.引入jpa和mysql驱动支持
在pom.xml上右键spring -> edit starters，勾选mysql、jpa；
可以看到pom新增依赖：mysql-connector-java、spring-boot-starter-data-jpa
<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.cy</groupId>

    <artifactId>HelloWorld</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <packaging>war</packaging>

    <name>HelloWorld</name>

    <description>Demo project for Spring Boot</description>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>2.0.0.RELEASE</version>

        <relativePath/> <!-- lookup parent from repository -->

    </parent>

    <properties>

        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>

        <java.version>1.8</java.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-tomcat</artifactId>

            <scope>provided</scope>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-test</artifactId>

            <scope>test</scope>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-configuration-processor</artifactId>

            <optional>true</optional>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-freemarker</artifactId>

        </dependency>

        <dependency>

            <groupId>mysql</groupId>

            <artifactId>mysql-connector-java</artifactId>

            <scope>runtime</scope>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-data-jpa</artifactId>

        </dependency>

    </dependencies>

    <build>

        <plugins>

            <plugin>

                <groupId>org.springframework.boot</groupId>

                <artifactId>spring-boot-maven-plugin</artifactId>

            </plugin>

        </plugins>

    </build>

</project>

2.src/main/resources/application.yml中配置server的根路径和port、数据源、showsql等：

server:

 port: 80

 servlet:

    context-path: /

spring:

  datasource:

    driver-class-name: com.mysql.jdbc.Driver

    url: jdbc:mysql://localhost:3306/db_book

    username: root

    password: root

  jpa:

    hibernate:

      ddl-auto: update

    show-sql: true

3.代码:

Book.java实体：

package com.cy.entity;

import javax.persistence.Column;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.Table;

@Entity

@Table(name="t_book")

public class Book {

    @Id

    @GeneratedValue

    private Integer id;

    @Column(length=100)

    private String name;

    @Column(length=50)

    private String author;

    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 String getAuthor() {

        return author;

    }

    public void setAuthor(String author) {

        this.author = author;

    }

}

com.cy.dao.BookDao.java:

package com.cy.dao;

import org.springframework.data.jpa.repository.JpaRepository;

import com.cy.entity.Book;

public interface BookDao extends JpaRepository<Book, Integer>{

}

CRUD的BookController.java:

package com.cy.controller;

import java.util.List;

import javax.annotation.Resource;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.PathVariable;

import org.springframework.web.bind.annotation.PostMapping;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.servlet.ModelAndView;

import com.cy.dao.BookDao;

import com.cy.entity.Book;

@Controller

@RequestMapping("/book")

public class BookController {

    @Resource

    private BookDao bookDao;

    /**

     * 查找所有图书

     */

    @RequestMapping("/list")

    public ModelAndView list(){

        ModelAndView mav = new ModelAndView();

        List<Book> bookList = bookDao.findAll();

        mav.addObject("bookList", bookList);

        mav.setViewName("bookList");

        return mav;

    }

    /**

     * 添加图书

     */

    @RequestMapping(value="/add", method=RequestMethod.POST)

    public String add(Book book){

        bookDao.save(book);

        return "redirect:/book/list";

    }

    /**

     * 根据id查找图书

     */

    @RequestMapping("/preUpdate/{id}")

    public ModelAndView preUpdate(@PathVariable("id") Integer id){

        ModelAndView mav = new ModelAndView();

        mav.addObject("book", bookDao.getOne(id));

        mav.setViewName("bookUpdate");

        return mav;

    }

    /**

     * 修改图书

     */

    @PostMapping("/update")

    public String update(Book book){

        bookDao.save(book); //依然是save，有id就修改，没有id就添加

        return "redirect:/book/list";

    }

    /**

     * 删除图书

     */

    @GetMapping("/delete")

    public String delete(Integer id){

        bookDao.deleteById(id);

        return "redirect:/book/list";

    }

}

src/main/resources/templates/bookList.ftl:

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>图书管理</title>

</head>

<body>

<a href="/bookAdd.html">添加</a>

<table>

    <tr>

        <th>编号</th>

        <th>图书名称</th>

        <th>图书作者</th>

        <th>操作</th>

    </tr>

    <#list bookList as book>

        <tr>

            <td>${book.id}</td>

            <td>${book.name}</td>

            <td>${book.author}</td>

            <td>

                <a href="/book/preUpdate/${book.id}">修改</a>

                <a href="/book/delete?id=${book.id}">删除</a>

            </td>

        </tr>

    </#list>

</table>

</body>

</html>

添加图书页面src/main/webapp/bookAdd.html:

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

<form action="/book/add" method="post">

    图书名称：<input type="text" name="name"/><br/>

    图书作者：<input type="text" name="author"/><br/>

    <input type="submit" value="提交"/>

</form>

</body>

</html>

修改图书页面：src/main/resources/templates/bookUpdate.ftl:

要注意修改这边要把book的id带过去，不然就成添加了；

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>图书修改</title>

</head>

<body>

<form action="/book/update" method="post">

    <input type="hidden" name="id" value="${book.id}"/>

    图书名称：<input type="text" name="name" value="${book.name}"/><br/>

    图书作者：<input type="text" name="author" value="${book.author}"/><br/>

    <input type="submit" value="提交"/>

</form>

</body>

</html>
测试：
1.项目启动，观察新建的表，（前提是mysql中已经新建了db_book这个数据库，因为mysql的url就是jdbc:mysql://localhost:3306/db_book）；
项目启动，自动建表，t_book：
mysql> show create table t_book;

+--------+--------------------------------------

------------------------------------------------

| Table  | Create Table

+--------+--------------------------------------

------------------------------------------------

| t_book | CREATE TABLE `t_book` (

  `id` int(11) NOT NULL auto_increment,

  `author` varchar(50) default NULL,

  `name` varchar(100) default NULL,

  PRIMARY KEY  (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8 |

+--------+--------------------------------------

------------------------------------------------

1 row in set (0.00 sec)
mysql> desc t_book;

+--------+--------------+------+-----+---------+----------------+

| Field  | Type         | Null | Key | Default | Extra          |

+--------+--------------+------+-----+---------+----------------+

| id     | int(11)      | NO   | PRI | NULL    | auto_increment |

| author | varchar(50)  | YES  |     | NULL    |                |

| name   | varchar(100) | YES  |     | NULL    |                |

+--------+--------------+------+-----+---------+----------------+

2.http://localhost/book/list，显示：

spring boot学习(4) SpringBoot 之Spring Data Jpa 支持（1）

进行增、删、改、list操作正常；

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