SpringBootMVC02——Spring Data JPA的使用&JSP的使用

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

<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>

<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