SpringBoot+Mybatis+Thymeleaf_基础开发

创建项目

通过idea的Spring Initializr来创建项目

Group一般是你组织的名字，例如：域名.公司名.项目名

artifact一般写为：项目-xxx

SpringBoot + Mybatis 简单的测试

1、基础配置

---

首先我们对环境进行配置，pom.xml的dependencies配置如下

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-thymeleaf</artifactId>
    </dependency>
    <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>
        <exclusions>
            <exclusion>
                <groupId>org.junit.vintage</groupId>
                <artifactId>junit-vintage-engine</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.17</version>
    </dependency>
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>2.0.0</version>
    </dependency>
</dependencies>

经过测试mybatis为默认，mysql为8.0.17，springboot只需要用默认的即可，thymeleaf也是用默认的即可。

然后对application.properties进行配置，配置如下：

spring.datasource.url=jdbc:mysql://localhost:3306/数据库名?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
spring.datasource.username=数据库登录账号
spring.datasource.password=数据库登录密码
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
mybatis.mapper-locations=classpath:mapping/*.xml    #locations目录默认以resources为根目录

2、SpringBoot + Mybatis 的层

---

一般情况下我们分为四层

controller层：调用service层的接口，进行业务操作。

entity层：entity层和model层等价，存放的是实体类，属性值与数据库中的属性值保持一致。实现set和get方法（这一步不可以少，少一个get或者set都不行，只需要默认的get和set即可）。

mapper层：dao层和mapper层等价，对数据库进行持久化操作，它的方法是针对数据库操作的，基本用到的就是增删改查。他只是定义一个接口，然后在mapper.xml中实现接口和数据库的交互。

service层：存放业务逻辑处理，不直接对数据库进行操作，有接口和接口实现类，提供controller层调用方法。

在resources类中创建一个包，用于存放Mapper.xml

具体分布如下图所示

3、代码实现

---

controller层：UserController

package com.example.demo.controller;
import com.example.demo.entity.User;
import com.example.demo.service.UserServiceImpl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
@RestController
@RequestMapping("/testBoot")
public class UserController {
    @Autowired
    private UserService userService;
    @RequestMapping(value = "/getUsers",method = RequestMethod.GET)
    public List<User> GetUsers(){
        return userService.getUsers();
    }
}

entity层：User

package com.example.demo.entity;
public class User {
    private Integer id;
    private String name;
    private String account;
    private String password;
    private String email;
    @Override
    public String toString() {
        return "id = " + getId();
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public Integer getId() {
        return id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void setAccount(String account) {
        this.account = account;
    }
    public String getAccount() {
        return account;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getPassword() {
        return password;
    }
    public void setEmail(String email) {
        this.email = email;
    }
    public String getEmail() {
        return email;
    }
}

mapper层：UserMapper

package com.example.demo.mapper;
import com.example.demo.entity.User;
import org.springframework.stereotype.Repository;
import java.util.List;
@Repository
public interface UserMapper {
    List<User> getUsers();
}

service层：UserService

package com.example.demo.service;
import com.example.demo.entity.User;
import com.example.demo.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import java.util.List;
@Service
@Transactional
public class UserService {
    @Autowired
    UserMapper userMapper;
    public List<User> getUsers() {
        return userMapper.getUsers();
    }
}

mapping.xml配置：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.example.demo.mapper.UserMapper">
    <resultMap id="user" type="com.example.demo.entity.User">
        <result column="id" jdbcType="INTEGER" property="id" />
        <result column="name" jdbcType="VARCHAR" property="name" />
        <result column="account" jdbcType="VARCHAR" property="account" />
        <result column="password" jdbcType="VARCHAR" property="password" />
        <result column="email" jdbcType="VARCHAR" property="email"/>
    </resultMap>
    <select id="getUsers" resultMap="user">
        select * from user
    </select>
</mapper>

运行效果：

注意事项：

1、如果service层@Autowired注解的变量出现了ERROR，但是运行时没有问题，请在Mapper层接口头部添加@Repository

2、请注意mapper.xml文件中的目录，若报错，请注意查看

带参数的输出某id的数据库数据

1、UserMapper.java需要加上getUser(Integer id)

package com.example.demo.mapper;
import com.example.demo.entity.User;
import org.springframework.stereotype.Repository;
import java.util.List;
@Repository
public interface UserMapper {
    List<User> getUsers();
    User getUser(Integer id);
}

2、UserService.java需要定义getUser(Integer id)

package com.example.demo.service;
import com.example.demo.entity.User;
import com.example.demo.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import java.util.List;
@Service
@Transactional
public class UserService {
    @Autowired
    UserMapper userMapper;
    public List<User> getUsers() {
        return userMapper.getUsers();
    }
    public User getUser(Integer id){
        return userMapper.getUser(id);
    }
}

3、UserController添加新的业务

import com.example.demo.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
@RestController
@RequestMapping("/testBoot")
public class UserController {
    @Autowired
    private UserService userService;
    @RequestMapping(value = "/getUsers",method = RequestMethod.GET)
    public List<User> getUsers(){
        return userService.getUsers();
    }
    @RequestMapping(value = "getUser",method = RequestMethod.GET)
    public User getUser(@RequestParam(value="id",required = true) Integer id){
        return userService.getUser(id);
    }
}

4、UserMapper.xml需要添加新的sql语句

<?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.mapper.UserMapper">
    <resultMap id="user" type="com.example.demo.entity.User">
        <result column="id" jdbcType="INTEGER" property="id" />
        <result column="name" jdbcType="VARCHAR" property="name" />
        <result column="account" jdbcType="VARCHAR" property="account" />
        <result column="password" jdbcType="VARCHAR" property="password" />
        <result column="email" jdbcaType="VARCHAR" property="email"/>
    </resultMap>
    <select id="getUsers" resultMap="user">
        select * from user
    </select>
    <select id="getUser" resultMap="user">
        select * from user
        <where>
            id = #{id}
        </where>
    </select>
</mapper>

运行效果

通过thymeleaf显示数据库数据

---

1、首先我们再创建一个view层，java代码类似于UserController，但是不同的是把restController替换为Controller，这样就可以跳转到指定的网页了，如果函数参数中带有model就可以传入数据到网页，通过thymeleaf来渲染网页。

2、UserView代码如下

package com.example.demo.view;

import com.example.demo.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
@Controller
@RequestMapping(value = "user_view")
public class UserView {
    @Autowired
    private UserService userService;
    @RequestMapping(value = "/test")
    public String user_view(@RequestParam(value = "id",required = false) Integer id, Model model){
        model.addAttribute("user_data",userService.getUser(id));
        return "index";
    }
}

3、接着我们开始写html，这里我们需要用到类似于EL语言的写法，代码如下

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<p th:text="${user_data.name}"></p>
</body>
</html>

运行效果如下：