SpringBootMVC02——Spring Data JPA的使用&JSP的使用
2024-09-20 23:15:34
Spring Data JPA的使用
实体层
package com.littlepage.domain; import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table; @Entity
@Table(name="city")
public class City {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
private String name;
public City() {
super();
}
public City(Integer id, String name) {
super();
this.id = id;
this.name = name;
}
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;
}
@Override
public String toString() {
return "City [id=" + id + ", name=" + name + "]";
}
}
Dao层只需要继承JPARepository就可以
package com.littlepage.dao; import org.springframework.data.jpa.repository.JpaRepository; import com.littlepage.domain.City; public interface CityRepository extends JpaRepository<City, Integer> { }
Service层的增删改查操作
package com.littlepage.service; import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import com.littlepage.dao.CityRepository;
import com.littlepage.domain.City; @Service
public class CityService {
@Autowired
CityRepository cityDao; public List<City> findAll(){
return cityDao.findAll();
} public String add(City city) {
if(cityDao.existsById(city.getId())) {
return "添加失败";
}
cityDao.save(city);
return "添加成功";
} public String remove(Integer id) {
if(cityDao.existsById(id)) {
cityDao.deleteById(id);;
return "删除成功";
}
return "不存在";
} public String modify(City city) {
if(!cityDao.existsById(city.getId())) {
return "不存在";
}
cityDao.save(city);
return "修改成功";
}
}
application.properties
spring.datasource.url=jdbc:mysql://120.78.206.78:3306/world
spring.datasource.username=root
spring.datasource.password=Root123..
JSP的使用
<!-- https://mvnrepository.com/artifact/javax.servlet/jstl -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-jasper -->
<dependency>
<groupId>org.apache.tomcat</groupId>
<artifactId>tomcat-jasper</artifactId>
<version>9.0.21</version>
</dependency>
添加依赖jasper和jstl
SpringBoot默认从main下寻址,在application.properties里面配一下前缀后缀
spring.mvc.view.prefix=/WEB-INF/jsp/
spring.mvc.view.suffix=.jsp
jsp中可以用jstl表达式取出scope域的内容
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> <!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body> <table> <tr>
<th>id</th>
<th>name</th>
</tr> <c:forEach items="${list}" var="item"> <tr>
<td>${item.id }</td>
<td>${item.name }</td> </tr> </c:forEach> </table>
</body>
</html>
controller代码
@Controller
@RequestMapping("city")
public class CityController { @Autowired
CityService citySrv; @RequestMapping("/jspp")
public String s(Model model) {
List<City> list=citySrv.findAll();
model.addAttribute("list",list);
return "list";
} }
显示截图
易错点:使用jsp一定要从maven中取消thymeleaf引擎,不然会报错误
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