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：
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：
进行增、删、改、list操作正常；