SpringBoot+Mybatis 框架之 @Select注解方式搭建
1、创建SpringBoot项目
两种方式：1、通过idea来New一个project项目。
2、登陆 https://start.spring.io/ 上面选择相应的配置，点击“Generate Project”按钮下载项目，完成项目初始化。
pom.xml文件的配置（其中mysql的maven配置可能会和你本地的不服，会报数据库连接的错误，如果出现这种问题，改一下数据库版本就可以）：
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.example</groupId> <artifactId>demo</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>demo</name> <description>Demo project for Spring Boot</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>1.5.9.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> <dependency> <groupId>org.mybatis.spring.boot</groupId> <artifactId>mybatis-spring-boot-starter</artifactId> <version>1.3.1</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web-services</artifactId> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <scope>runtime</scope> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <!--集成日志logback+slf4j --> <!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api --> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> <version>1.7.2</version> </dependency> </dependencies> <!--<packaging>jar</packaging>--> <build> <finalName>demo</finalName> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
application.properties文件中的配置项（端口、数据库配置、debug、mybatis）
#项目的启动端口 server.port=9090 #数据库的配置 spring.datasource.url=jdbc:mysql://localhost:3306/DBName?useUnicode=true&characterEncoding=utf-8&useSSL=true spring.datasource.username= USERNAME spring.datasource.password= PASSWORD spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver #显示标准输出 logging.level.com.shyroke.mapper=debug #路径是是实体类的路径，和写在所有Mapper文件中用来扫描Mapper文件的@Mapper注解联用 mybatis.type-aliases-package=com.web.test.test.domain
2、项目内部结构
3、项目的最小功能代码
这个例子是实现一个简单的查询功能：
Controller层：
package com.web.test.test.controller;
import com.web.test.test.service.TeacherService;
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.RestController;
@RestController
public class TeacherController {
@Autowired
private TeacherService teacherService;
//Select By Id
@RequestMapping("/showTeacher/{id}")
public String selectTeacher(@PathVariable int id){
return teacherService.selectTeacher(id).toString();
}
//Select All
@RequestMapping("/selectAll")
public String selectAll(){
return teacherService.selectAll().toString();
}
* 有的朋友想在return的时候直接跳转界面去，看到@RestController了吗，这个是ResponseBody和Controller的集合，意思是return的数据都变成json的格式，返回到前端，不会跳转界面。
如果想跳转页面的话，就需要把RestController改成Controller，就会跳转页面了。
* 还有些朋友想带着数据返回到重新定义的页面去，对于这种需求，我建议使用“视图解释器解析”——ModelAndVIew。ModelAndView的用法类似于这样：
@RequestMapping
public ModelAndView list(Model model) {
model.addAttribute("userList", userRepository.listUsers());
model.addAttribute("title", "用户管理");
// new ModelAndView(目标页面的路径, 目标页面接到的返回值名称, api封装好返回的数据)
return new ModelAndView("users/list","userModel",model);
}
Service层：
package com.we b.test.test.service;
import com.web.test.test.domain.Teacher;
import java.util.List;
public interface TeacherService {
Teacher selectTeacher(int id);
List<Teacher> selectAll();
}
Service层的实现类，在Service文件夹下的Impl文件夹中：
package com.test.test.Service.impl;
import com.test.test.Service.TeacherService;
import com.test.test.domain.Teacher;
import com.test.test.mapper.TeacherMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import java.util.List;
@Service
public class TeacherImpl implements TeacherService {
@Autowired
TeacherMapper mapper;
@Override
public Teacher selectTeacher(int id) {
return mapper.selectTeacher(id);
}
@Override
public List<Teacher> selectAll() {
return mapper.selectAll();
}
}
Mapper 相当于DAO层:
package com.we b.test.test.mapper;
import com.web.test.test.domain.Teacher;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;
import java.util.List;
@Mapper
public interface TeacherMapper {
@Select ("SELECT * FROM Teacher WHERE id = #{id}")
Teacher selectTeacher(int id);
@Select("SELECT * FROM TEACHER WHERE 1=1")
List<Teacher> selectAll();
}
Domain 实体类：
package com.web.test.test.domain;
public class Teacher {
private int id;
private String name;
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getId() {
return id;
}
@Override
public String toString() {
return "Teacher{" +"id=" + id +", name='" + name + '\'' +'}';
}
}
这样就能实现@Select标签的方式搭建SpringBoot的Mybatis框架了。挺简单的，但是我不太喜欢用这种当时，Mybatis的继承方式三种：@Select、@Provider、还有xml映射文件的方式。
@Select的方式写得太死了，不够灵活。更多的还是使用另外两种方式。这两天我会再介绍另外两种方式。
