我的第一个java项目

安装了idea软件且本地通过cmd 命令启动了mysql。还安装了java sdk。

总结spring-boot通过resource下的mapping文件下的文件xml语法来增删查改(因为使用了MyBatis，MyBatis 的真正强大在于它的语句映射，这是它的魔力所在。由于它的异常强大，映射器的 XML 文件就显得相对简单)，xml语法的属性id和resultType与java下的文件名和path有关系

通过idea建立spring-boot项目，java 1.8 spring-boot 2.6.13。项目文件目录

项目第一次运行时，得通过idea软件右键执行sql文件

项目运行时得run main方法文件(FirstJavaProApplication)

在这里插入图片描述

sql文件夹下的createUser.sql

CREATE TABLE `user` (
                         `id` int NOT NULL,
                         `name` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
                         `salary` double(10,2) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb3 COLLATE=utf8_unicode_ci;

src/main/java/com.byd.firstjavapro/controller/UserController.java

package com.byd.firstjavapro.controller;

import com.byd.firstjavapro.entity.User;
import com.byd.firstjavapro.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import javax.xml.ws.Service;
import java.util.List;


@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired
    private UserService userService;
    //通过id得到用户信息
    // demo http://localhost:3000/user/getUser/19
    @RequestMapping(value = "/getUser/{id}", method = RequestMethod.GET)
    public String getUser(@PathVariable int id){
        return userService.getUser(id).toString();
    }
    //通过id删除用户信息
    // http://localhost:3000/user/delete?id=1
    @RequestMapping(value = "/delete", method = RequestMethod.GET)
    public String delete(int id){
        int result = userService.delete(id);
        if(result >= 1){
            return "删除成功！";
        }else{
            return "删除失败！";
        }
    }
    //更改用户信息
    //http://localhost:3000/user/update?id=19&name=小王&salary=12000
    @RequestMapping(value = "/update", method = RequestMethod.GET)
    public String update(User user){
        int result = userService.update(user);
        if(result >= 1){
            return "更新成功！";
        }else{
            return "更新失败！";
        }
    }
    //插入用户信息
    // http://localhost:3000/user/insert?id=15&name=浩子&salary=13000
    @RequestMapping(value = "/insert", method = RequestMethod.GET)
    public int insert(User user){
        return userService.save(user);
    }
    //查询所有用户的信息
    // http://localhost:3000/user/selectAll
    @RequestMapping(value = "/selectAll")
    @ResponseBody   //理解为：单独作为响应体，这里不调用实体类的toString方法
    public List<User>  listUser(){
        return userService.selectAll();
    }
}

src/main/java/com.byd.firstjavapro/entity/User.java

package com.byd.firstjavapro.entity;

/**
 * @description:    实体类
 * @author: Fish_Vast
 * @Date: 2021/8/25
 * @version: 1.0
 */
public class User {
    private String name;
    private Integer id;
    private Double salary;

    public User() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Double getSalary() {
        return salary;
    }

    public void setSalary(Double salary) {
        this.salary = salary;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", id=" + id +
                ", salary=" + salary +
                '}';
    }
}

src/main/java/com.byd.firstjavapro/mapper/UserMapper.java

package com.byd.firstjavapro.mapper;
import  com.byd.firstjavapro.entity.User;

import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
public interface UserMapper {
    //1.通过id查询用户信息
    User getUser(int id);
    //2.通过id删除用户信息
    int delete(int id);
    //3.更改用户信息
    int update(User user);
    //4.插入用户信息
    int save(User user);
    //5.查询所有用户信息
    List<User> selectAll();
}

src/main/java/com.byd.firstjavapro/service/UserService.java

package com.byd.firstjavapro.service;

import com.byd.firstjavapro.entity.User;
import com.byd.firstjavapro.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserService {
    @Autowired
    private UserMapper userMapper;

    public User getUser(int id){
        return userMapper.getUser(id);
    }

    public int delete(int id){
        return userMapper.delete(id);
    }

    public int update(User user){
        return userMapper.update(user);
    }

    public int save(User user){
        return userMapper.save(user);
    }

    public List<User>  selectAll(){
        return userMapper.selectAll();
    }
}

src/main/java/com.byd.firstjavapro/FirstJavaProApplication.java

package com.byd.firstjavapro;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.mybatis.spring.annotation.MapperScan;
@MapperScan("com.byd.firstjavapro.mapper")

@SpringBootApplication
public class FirstJavaProApplication {

    public static void main(String[] args) {
        SpringApplication.run(FirstJavaProApplication.class, args);
    }

}

下面是main文件下resources文件夹
src/main/resources/mapping/UserMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.byd.firstjavapro.mapper.UserMapper">
    <resultMap id="BaseResultMap" type="com.byd.firstjavapro.entity.User">
        <result column="id" jdbcType="INTEGER" property="id" />
        <result column="name" jdbcType="VARCHAR" property="name" />
        <result column="salary" jdbcType="DOUBLE" property="salary" />
    </resultMap>
    <!--查询用户信息-->
    <select id="getUser" resultType="com.byd.firstjavapro.entity.User">
        select * from user where id = #{id}
    </select>
    <!--删除用户信息-->
    <delete id="delete" parameterType="int">
        delete from user where id=#{id}
    </delete>
    <!--返回所有用户信息-->
    <select id="selectAll"  resultType="com.byd.firstjavapro.entity.User">
        select * from user
    </select>

    <!--增加用户信息-->
    <insert id="save" parameterType="com.byd.firstjavapro.entity.User" >
        insert into user
        <trim prefix="(" suffix=")" suffixOverrides="," >
            <if test="id != null" >
                id,
            </if>
            <if test="name != null" >
                name,
            </if>
            <if test="salary != null" >
                salary,
            </if>
        </trim>
        <trim prefix="values (" suffix=")" suffixOverrides="," >
            <if test="id != null" >
                #{id,jdbcType=INTEGER},
            </if>
            <if test="name != null" >
                #{name,jdbcType=VARCHAR},
            </if>
            <if test="salary != null" >
                #{salary,jdbcType=DOUBLE},
            </if>
        </trim>
    </insert>

    <!--根据id更改用户信息-->
    <update id="update" parameterType="com.byd.firstjavapro.entity.User">
        update user
        <set >
            <if test="name != null" >
                name = #{name,jdbcType=VARCHAR},
            </if>
            <if test="salary != null" >
                salary = #{salary,jdbcType=DOUBLE},
            </if>
        </set>
        where id = #{id,jdbcType=INTEGER}
    </update>
</mapper>

src/main/resources/static/index.html

<html>
<body>
<h1>hello word!!!</h1>
<p>this is a html page</p>
</body>
</html>

src/main/resources/application.properties

server.port=3000
spring.datasource.url=jdbc:mysql://localhost:3306/test
spring.datasource.username=root
spring.datasource.password=123456
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

#mybatis??
mybatis.mapper-locations= classpath:mapping/*.xml
mybatis.type-aliases-package= com.byd.firstjavapro.entity

根目录下的
pom.xml文件(从这个文件可以看出这个项目用的java1.8版本，spring-boot版本2.16.13版本)

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.byd</groupId>
    <artifactId>firstJavaPro</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>firstJavaPro</name>
    <description>firstJavaPro</description>
    <properties>
        <java.version>1.8</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <spring-boot.version>2.6.13</spring-boot.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-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.mybatis.spring.boot/mybatis-spring-boot-starter -->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.2.2</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${spring-boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>${spring-boot.version}</version>
                <configuration>
                    <mainClass>com.byd.firstjavapro.FirstJavaProApplication</mainClass>
                    <skip>true</skip>
                </configuration>
                <executions>
                    <execution>
                        <id>repackage</id>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>