IDEA开发实现Maven+Servlet+Mybatis实现CRUD管理系统-入门篇

叁歲伎倆 2024-03-22 16:46 20阅读 0赞

### 创建数据库 ###

create database mybatis;
    use mybatis;
    
    drop table if exists tb_user;
    
    create table tb_user(
    	id int primary key auto_increment,
    	username varchar(20),
    	password varchar(20),
    	gender char(1),
    	addr varchar(30)
    );
    
    INSERT INTO tb_user VALUES (1, 'zhangsan', '123', '男', '北京');
    INSERT INTO tb_user VALUES (2, '李四', '234', '女', '天津');
    INSERT INTO tb_user VALUES (3, '王五', '11', '男', '西安');

### **在项目的 resources 目录下创建logback的配置文件** ###

<?xml version="1.0" encoding="UTF-8"?>
    <configuration>
        
        <appender name="Console" class="ch.qos.logback.core.ConsoleAppender">
            <encoder>
                <pattern>[%level] %blue(%d{HH:mm:ss.SSS}) %cyan([%thread]) %boldGreen(%logger{15}) - %msg %n</pattern>
            </encoder>
        </appender>
    
        <logger name="com.ruanjian" level="DEBUG" additivity="false">
            <appender-ref ref="Console"/>
        </logger>
    
    
        
        <root level="DEBUG">
            <appender-ref ref="Console"/>
        </root>
    </configuration>

### **编写 MyBatis 核心配置文件 – > 替换连接信息 解决硬编码问题 在模块下的 resources 目录下创建mybatis的配置文件 mybatis-config.xml，内容如下：** ###

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE configuration
            PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
    
        <typeAliases>
            <package name="com.ruanjian.pojo"/>
        </typeAliases>
        
        
        <environments default="development">
            <environment id="development">
                <transactionManager type="JDBC"/>
                <dataSource type="POOLED">
                    
                    <property name="driver" value="com.mysql.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql:///mybatis?useSSL=false"/>
                    <property name="username" value="root"/>
                    <property name="password" value="1234"/>
                </dataSource>
            </environment>
    
            <environment id="test">
                <transactionManager type="JDBC"/>
                <dataSource type="POOLED">
                    
                    <property name="driver" value="com.mysql.jdbc.Driver"/>
                    <property name="url" value="jdbc:mysql:///mybatis?useSSL=false"/>
                    <property name="username" value="root"/>
                    <property name="password" value="1234"/>
                </dataSource>
            </environment>
        </environments>
        <mappers>
           
           <mapper resource="UserMapper.xml"/>
        </mappers>
    </configuration>

### **编写 SQL 映射文件 --> 统一管理sql语句，解决硬编码问题 在模块的 resources 目录下创建映射配置文件 UserMapper.xml，内容如下：** ###

<?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="test">
        <select id="selectAll" resultType="com.ruanjian.pojo.User">
            select * from tb_user;
        </select>
    </mapper>

### ● Java编码 ###

○ 在 com.ruanjian.pojo 包下创建 User类。

public class User {
        
        private int id;
        private String username;
        private String password;
        private String gender;
        private String addr;
    
        // setter 和 getter
    
        public void setId(int id) {
        
            this.id = id;
        }
    
        public void setUsername(String username) {
        
            this.username = username;
        }
    
        public void setPassword(String password) {
        
            this.password = password;
        }
    
        public void setGender(String gender) {
        
            this.gender = gender;
        }
    
        public void setAddr(String addr) {
        
            this.addr = addr;
        }
    
        public int getId() {
        
            return id;
        }
    
        public String getUsername() {
        
            return username;
        }
    
        public String getPassword() {
        
            return password;
        }
    
        public String getGender() {
        
            return gender;
        }
    
        public String getAddr() {
        
            return addr;
        }
    //to String
        @Override
        public String toString() {
        
            return "User{" +
                    "id=" + id +
                    ", username='" + username + '\'' +
                    ", password='" + password + '\'' +
                    ", gender='" + gender + '\'' +
                    ", addr='" + addr + '\'' +
                    '}';
        }
    }

在 com.ruanjian 包下编写 MybatisDemo 测试类

public class MyBatisDemo {
        
    
        public static void main(String[] args) throws IOException {
        
            //1. 加载mybatis的核心配置文件，获取 SqlSessionFactory
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    
            //2. 获取SqlSession对象，用它来执行sql
            SqlSession sqlSession = sqlSessionFactory.openSession();
            //3. 执行sql
            List<User> users = sqlSession.selectList("test.selectAll"); //参数是一个字符串，该字符串必须是映射配置文件的namespace.id
            System.out.println(users);
            //4. 释放资源
            sqlSession.close();
        }
    }

### 运行结果 ###

![在这里插入图片描述][e58a344302e94dfcb640580ade081aff.png]

[e58a344302e94dfcb640580ade081aff.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/22/3497d037537a4d62abf8855d6b34412b.png