学生信息查询系统

一、步骤

1.引入相关依赖pom.xml

<?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.zjd</groupId>
    <artifactId>Part3</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.2</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.11</version>
        </dependency>
    </dependencies>
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>

</project>

2.导入数据库数据

1、新建数据库mybatis

CREATE DATABASE mybatis;

2、在mybatis数据库下创建表student

CREATE TABLE `student` (
                           `id` int NOT NULL AUTO_INCREMENT,
                           `name` varchar(20) NOT NULL,
                           `major` varchar(20) NOT NULL,
                           PRIMARY KEY (`id`)
);

3、在student表中插入数据

INSERT INTO student(id, name, major)
VALUES
(1,'张三','英语'),
(1,'李四','英语'),
(1,'王五','历史'),
(1,'张柳','计算机'),
(1,'孙悟空','数学');

3.创建连接数据库配置文件db.properties

# MySQL的版本在8.0之下的，mysql.driver=com.mysql.jdbc.Driver
mysql.driver=com.mysql.cj.jdbc.Driver
mysql.url=jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&characterEncoding=utf8&useUnicode=true&useSSL=false
mysql.username=root
mysql.password=root

4.创建myBatis的核心配置文件mybatis-config.xml

<?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>
    <properties resource="db.properties"/>
    <settings>
        <setting name="cacheEnabled" value="true"/>
        <setting name="lazyLoadingEnabled" value="true"/>
    </settings>
    <typeAliases>
        <package name="com.zjd.pojo"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${mysql.driver}"/>
                <property name="url" value="${mysql.url}"/>
                <property name="username" value="${mysql.username}"/>
                <property name="password" value="${mysql.password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/zjd/mapper/StudentMapper.xml"/>
    </mappers>
</configuration>

5.创建student的实体类Student.java

package com.zjd.pojo;

public class Student {
    private int id;
    private String name;
    private String major;

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

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getMajor() {
        return major;
    }

    public void setMajor(String major) {
        this.major = major;
    }
}

6.创建student的映射文件StudentMapper.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.zjd.pojo.Student">
    <select id="findStudent" parameterType="Student" resultType="Student">
        select * from student
        <where>
        <choose>
            <when test="name!=null and name!=''">
                and name like concat('%',#{name},'%')
            </when>
            <when test="major!=null and major!=''">
                and major=#{major}
            </when>
            <otherwise>
                and id is not null
            </otherwise>
        </choose>
        </where>
    </select>
    <select id="findById" parameterType="java.util.Arrays" resultType="Student">
        select * from student where id in
        <foreach collection="list" open="(" separator="," close=")" index="index" item="id">
            #{id}
        </foreach>
    </select>
</mapper>

7.将映射文件加载到mybatis-config.xml中

<!--  上图我已加载过  -->
<mappers>
        <mapper resource="com/zjd/mapper/StudentMapper.xml"/>
</mappers>

8.创建MyBatis的工具类MyBatisUtils.java

package com.zjd.utils;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.Reader;

public class MyBatisUtils {
    public static SqlSessionFactory sqlSessionFactory=null;
    static {
        try{
            Reader reader= Resources.getResourceAsReader("mybatis-config.xml");
            sqlSessionFactory= new SqlSessionFactoryBuilder().build(reader);
        }catch (IOException e){
            e.printStackTrace();
        }
    }
    public static SqlSession getSession(){
        return sqlSessionFactory.openSession();
    }
}

9.创建测试类StudentTest.java测试运行

package Test;

import com.zjd.pojo.Student;
import com.zjd.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.util.ArrayList;
import java.util.List;

public class StudentTest {
    SqlSession session=null;
    @Before
    public void Before(){
        session= MyBatisUtils.getSession();
    }
    @Test
    public void findStudent(){
        Student student=new Student();
        student.setId(2);
        //student.setName("张");
        //student.setMajor("计算机");
        List<Student> students= session.selectList("com.zjd.pojo.Student.findStudent",student);
        for (Student student1:students
             ) {
            System.out.println(student1);
        }
    }
    @Test
    public void findById(){
        Student student=new Student();
        List<Integer> ids=new ArrayList<Integer>();
        for (int i = 1; i < 5; i++) {
            ids.add(i);
        }
        List<Student> students= session.selectList("com.zjd.pojo.Student.findById",ids);
        for (Student student1:students
        ) {
            System.out.println(student1);
        }
    }
    @After
    public void After(){
        session.commit();
        session.close();
    }
}

二、项目结构

三、本次完成案例：学生信息查询系统

（1）多条件查询

当用户输入的姓名不为空时，只根据学生姓名进行信息的查询

当用户输入的姓名为空而专业不为空时，则只根据学生专业进行学生信息的查询

当用户输入的姓名和专业都为空，则要求查询出所有学号不为空的学生信息

（2）单条件查询

查询出所有id值小于5的学生的信息

四、重要讯息！！！！！

各位小伙伴有疑问可以私聊我，我会在每周日统一查看回复

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五、下方评论区见该案例源代码

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