spring boot + mybatis+freemarker +mysql 实例演示

蔚落 2021-12-05 06:15 205阅读 0赞

###  ###

*   *  step 1 新建工程
     *  step 2 application.yml配置文件
     *  step 3 配置mysql 数据
     *  step 4 新建ftl 页面文件
     *  step 5 user 相关代码
     *  step 6 新建 UserMapper 配置文件
     *  step 7 启动工程 ，访问页面
     *  总结:

## step 1 新建工程 ##

选择 spring boot devtools ，  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3doYW5kZ2Ro_size_16_color_FFFFFF_t_70]  
等同于下面引入 devtools依赖包

<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-devtools</artifactId>
    			<optional>true</optional> 
    			
    		</dependency>

选择 spring web starter  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3doYW5kZ2Ro_size_16_color_FFFFFF_t_70 1]  
等同于

<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-web</artifactId>
    		</dependency>

选择 apache freemarker  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3doYW5kZ2Ro_size_16_color_FFFFFF_t_70 2]  
等同于

<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-freemarker</artifactId>
    		</dependency>

选择mybatis和mysql driver  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3doYW5kZ2Ro_size_16_color_FFFFFF_t_70 3]  
注意这里还是不要 选择mysql driver，不然引入的依赖包版本太高，可能不使用本地mysql版本，本例  
选择后，引入的mysql driver 版本是 8.以上，导致程序报错。  
等同于引入依赖

<dependency>
    			<groupId>mysql</groupId>
    			<artifactId>mysql-connector-java</artifactId>
    			<version>5.1.21</version>
    		</dependency>
    <dependency>
    			<groupId>org.mybatis.spring.boot</groupId>
    			<artifactId>mybatis-spring-boot-starter</artifactId>
    			<version>2.1.0</version>
    		</dependency>

## step 2 application.yml配置文件 ##

spring:
    # freemarker 配置
      freemarker:
        template-loader-path: classpath:/templates/view/
        cache: false
        charset: utf-8
        check-template-location: true
        content-type: text/html
        expose-request-attributes: false
        expose-session-attributes: false
        request-context-attribute: request
        suffix: .ftl
      # mysql 数据源
      datasource:
        url: jdbc:mysql://127.0.0.1:3306/student?useUnicode=true&characterEncoding=UTF-8
        username: root
        password: root
        driverClassName: com.mysql.jdbc.Driver
    mybatis:
      mapper-locations: classpath:mapper/*.xml
      type-aliases-package: com.example.app.user.dto

注意这里 datasource 必须挨着spring ，如果datasource 放在 mybatis后面，  
则需要再加上spring

## step 3 配置mysql 数据 ##

新建 t\_user 表，并插入数据

CREATE TABLE t_user (
       user_id   int(5) NOT NULL AUTO_INCREMENT comment '用户id' ,
      name varchar(20)  comment '用户名称' ,
      passwd varchar(20)  comment '用户密码' ,
       phone varchar(20)  comment '电话'  ,
       remark varchar(20)  comment '备注'  ,
      PRIMARY KEY (user_id)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 comment '用户信息表';
    
    
    insert into t_user(name,passwd,phone,remark) values('孙悟空','123456','1388888888','七十二变');
    insert into t_user(name,passwd,phone,remark) values('唐三藏','123456','1311111111','大唐佛法');
    insert into t_user(name,passwd,phone,remark) values('猪八戒','123456','1322222222','好色好吃');
    insert into t_user(name,passwd,phone,remark) values('沙和尚','123456','1322222222','勤劳老实');

## step 4 新建ftl 页面文件 ##

文件路径放在 templates\\view 下，在 templates下新建路径 view ，然后新建ftl文件 showAllUsers.ftl

<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    </head>
    <body>
    <div>
        <span>hello world! this is spring boot and  mybatis and freemarker</span>
        <table border="1px">
        <#list datas as user>
            <tr><td>${user.user_id}</td><td> ${(user.name)!}</td><td>${(user.remark)!}</td></tr>
            
        </#list>
        </table>
    </div>
    </body>
    
    </html>

## step 5 user 相关代码 ##

新建 包 user.dao ,user.dto,user.service,user.serviceimpl,以及controller 结构如下  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3doYW5kZ2Ro_size_16_color_FFFFFF_t_70 4]  
新建java 类UserDto

package com.example.demo.user.dto;
    
    public class UserDto {
        private Integer user_id;
        private String username;
        private String passwd;
        private String phone;
        private String remark;
    
        public Integer getUser_id() {
            return user_id;
        }
    
        public void setUser_id(Integer user_id) {
            this.user_id = user_id;
        }
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public String getPasswd() {
            return passwd;
        }
    
        public void setPasswd(String passwd) {
            this.passwd = passwd;
        }
    
        public String getPhone() {
            return phone;
        }
    
        public void setPhone(String phone) {
            this.phone = phone;
        }
    
        public String getRemark() {
            return remark;
        }
    
        public void setRemark(String remark) {
            this.remark = remark;
        }
    }

UserDao 接口

package com.example.demo.user.dao;
    
    import com.example.demo.user.dto.UserDto;
    import org.apache.ibatis.annotations.Mapper;
    import org.springframework.stereotype.Repository;
    
    import java.util.List;
    
    @Repository
    @Mapper
    public interface UserDao {
        public List<UserDto> getUsers();
    }

UserService 接口

package com.example.demo.user.service;
    
    import com.example.demo.user.dto.UserDto;
    
    import java.util.List;
    
    public interface UserService {
        public List<UserDto> getUsers();
    }

UserService 接口 实现类

package com.example.demo.user.service.impl;
    
    import com.example.demo.user.dao.UserDao;
    import com.example.demo.user.dto.UserDto;
    import com.example.demo.user.service.UserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Service;
    
    import java.util.List; 
    @Service(value = "userService")
    public class UserServiceImpl implements UserService {
        @Autowired
        private UserDao userDao;
    
        @Override
        public List<UserDto> getUsers() {
            return userDao.getUsers();
        }
    }

UserController 控制类

package com.example.demo.controller;
    
    import com.example.demo.user.dto.UserDto;
    import com.example.demo.user.service.UserService;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    
    import java.util.List;
    import java.util.Map;
     
    @Controller
    public class UserController {
        @Autowired
        UserService userService;
        @RequestMapping("/showAllUsers")
        public String showAllUser(Map<String,Object> map){
            List<UserDto> users=userService.getUsers();
            map.put("datas",users);
            return "showAllUsers";
    
        }
    }

DemoApplication 代码如下：

package com.example.demo;
    
    import org.mybatis.spring.annotation.MapperScan;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
     @MapperScan("com.example.demo.user.dao")
    @SpringBootApplication
    public class DemoApplication {
    
    	public static void main(String[] args) {
    		SpringApplication.run(DemoApplication.class, args);
    	}
    
    }

## step 6 新建 UserMapper 配置文件 ##

在resource 目录下 新建mapper目录，再新建UserMapper 配置文件

<?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.example.demo.user.dao.UserDao" >
        <select id="getUsers" resultType="com.example.demo.user.dto.UserDto">
            select * from t_user
        </select>
    </mapper>

工程整体结构  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3doYW5kZ2Ro_size_16_color_FFFFFF_t_70 5]

## step 7 启动工程 ，访问页面 ##

[http://127.0.0.1:8080/showAllUsers][http_127.0.0.1_8080_showAllUsers]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3doYW5kZ2Ro_size_16_color_FFFFFF_t_70 6]

## 总结: ##

一般启动解析application.yml错误就是application.yml配置文件格式不规范导致，一定要细心。  
配置application.yml文件时一定要注意各个配置间上下级关系，以及同级配置必须有相同的空格缩进，  
不能使用tab。其次mysql driver 依赖包选择一定要合适，本例mysql 版本是5.7，所以选择了mysql-connector-java  
版本是5.1.21。

路漫漫其修远兮，吾将上下而求索。

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[http_127.0.0.1_8080_showAllUsers]: http://127.0.0.1:8080/showAllUsers
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