Spring Boot数据库操作之基本的JDBC访问和JDBCTemplate使用

作者：谭东

我们先看下最基础的JDBC的使用方式吧。我们这里使用MySQL。电脑里可以安装个mysql，便于本地测试使用。

Mysql下载地址：https://dev.mysql.com/downloads/

下载后，解压mysql压缩包到某一文件件，在根目录新建my.ini文件，写入配置：

[mysqld]
character-set-server=utf8 
collation-server=utf8_general_ci 

[mysql]
default-character-set = utf8

[mysql.server]
default-character-set = utf8


[mysqld_safe]
default-character-set = utf8


[client]
default-character-set = utf8

管理员身份运行cmd命令窗口。切换到mysql的bin文件夹下。输入命令：mysqld --install。

安装完毕，然后初始化：mysqld --initialize。启动服务：net start mysql。

登录mysql：mysql -u root -p，首次登陆一般是没有密码的，如果你安装的是mysql 5.7及以上版本，默认是有个随机密码了。

需要手动在mysql目录下搜索*.err，以文本形式打开才能看到如下内容：

[Note] A temporary password is generated for root@localhost: ?g#4:Yju&1Kp

红色部分为密码。这样登录成功后再去修改密码即可：alter user root@localhost identified by 'Mysql123456'。新密码最好有大写字母，小写字母和数字。

最后我们创建个数据库：create database student。

然后在student数据库里创建student表：create table student(id int primary key auto_increment,name varchar(100),sex varchar(10),age int,tel varchar(60));

在之前的pom.xml里引入mysql库。

<dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.9-rc</version>
        </dependency>

application.properties里加入mysql配置信息。

server.port=8082
spring.datasource.url=jdbc:mysql://localhost:3306/student?serverTimezone=GMT=&useUnicode=true&characterEncoding=utf-8&useSSL=true
spring.datasource.username=root
spring.datasource.password=Mysql123456
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

编写JDBC工具类。

package com.tandong.testjavaweb.utils;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class JDBCUtils {
    // mysql 连接参数
    private static String jdbcDriver = null;
    private static String url = null;
    private static String user = null;
    private static String password = null;
    private static boolean isCfg = false; // 记录是否读取过jdbc.properties文件配置 、避免多次读取
    // 线程安全的懒汉模式单例
    private static JDBCUtils jdbcUtils = null;

    public static synchronized JDBCUtils getInstance() {
        if (jdbcUtils == null) {
            if (!isCfg) {
                initJDBCParameter();
            }
            return jdbcUtils = new JDBCUtils();
        }
        return jdbcUtils;
    }

    /**
     * 读取属性文件中的mysql配置
     */
    private static void initJDBCParameter() {
        Properties properties = new Properties();
        InputStream in = JDBCUtils.class.getResourceAsStream("/application.properties");//加载 application.properties资源文件，如果该文件在包内则加包名
        try {
            properties.load(in);
            in.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        if (jdbcDriver == null || url == null || user == null || password == null) {
            jdbcDriver = properties.getProperty("spring.datasource.driver-class-name");
            url = properties.getProperty("spring.datasource.url");
            user = properties.getProperty("spring.datasource.username");
            password = properties.getProperty("spring.datasource.password");
            isCfg = true;
        }
    }

    /**
     * 获取数据连接
     *
     * @return
     * @throws Exception
     */
    public Connection getConnection() throws Exception {
        Class.forName(jdbcDriver);
        return DriverManager.getConnection(url, user, password);
    }

    /**
     * 释放数据库链接资源
     *
     * @param con  // 数据库连接对象
     * @param stmt // 执行sql操作对象
     * @param rs   // 查询结果集对象
     */
    public void closeConnection(Connection con, Statement stmt, ResultSet rs) {
        try {
            if (rs != null) {
                rs.close();
            }
            if (stmt != null) {
                stmt.close();
            }
            if (con != null) {
                con.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

编写个Student实体类。

package com.tandong.testjavaweb.entity;

public class Student {
    public int id;
    public String name;
    public String sex;
    public int age;
    public String tel;

    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 getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getTel() {
        return tel;
    }

    public void setTel(String tel) {
        this.tel = tel;
    }

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

编写StudentDao类。

package com.tandong.testjavaweb.dao;

import com.tandong.testjavaweb.entity.Student;

import java.sql.SQLException;
import java.util.List;

public interface StudentsDao {

    //添加方法
    void add(Student s) throws SQLException;

    //更新方法
    void update(Student s) throws SQLException;

    //删除方法
    void delete(int id) throws SQLException;

    //查找方法
    Student findById(int id) throws SQLException;

    //查找所有
    List<Student> findAll()throws SQLException;
}

编写StudentDao的实现类，StudentDaoImpl。

package com.tandong.testjavaweb.dao;

import com.tandong.testjavaweb.entity.Student;
import com.tandong.testjavaweb.utils.JDBCUtils;
import org.springframework.stereotype.Service;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

@Service
public class StudentsDaoImpl implements StudentsDao {
    @Override
    public void add(Student s) throws SQLException {
        Connection conn = null;
        PreparedStatement ps = null;
        String sql = "insert into student(id,name,sex,age,tel)values(?,?,?,?,?)";
        try {
            conn = JDBCUtils.getInstance().getConnection();
            ps = conn.prepareStatement(sql);
            ps.setInt(1, s.id);
            ps.setString(2, s.name);
            ps.setString(3, s.sex);
            ps.setInt(4, s.age);
            ps.setString(5, s.tel);
            ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
            throw new SQLException("添加数据失败！");
        } finally {
            JDBCUtils.getInstance().closeConnection(conn, ps, null);
        }
        System.out.println("数据添加成功！");
    }

    @Override
    public void update(Student s) throws SQLException {
        Connection conn = null;
        PreparedStatement ps = null;
        if (s == null) return;
        // 根据对象属性 拼接 更新sql
        String sql = "update student set ";
        StringBuilder sb = new StringBuilder(sql);
        sb.append("name=?");
        sb.append(",sex=?");
        sb.append(",tel=?");
        if (s.age != 0) sb.append(",age=?");
        if (s.id != 0) sb.append("where id=?");
        // 如果sql语句和原始语句一样，或者 没有包含条件语句不允许执行
        if (sb.toString().equals(sql) || sb.toString().contains("where")) return;
        try {
            conn = JDBCUtils.getInstance().getConnection();
            ps = conn.prepareStatement(sql);
            ps.setString(1, s.name);
            ps.setInt(2, s.age);
            ps.setString(3, s.sex);
            ps.setString(4, s.tel);
            ps.setInt(5, s.id);
            ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
            throw new SQLException("更新数据失败");
        } finally {
            JDBCUtils.getInstance().closeConnection(conn, ps, null);
        }
        System.out.println("数据更新成功！");
    }

    @Override
    public void delete(int id) throws SQLException {
        Connection conn = null;
        PreparedStatement ps = null;
        String sql = "delete from student where id=?";
        try {
            conn = JDBCUtils.getInstance().getConnection();
            ps = conn.prepareStatement(sql);
            ps.setInt(1, id);
            ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
            throw new SQLException(" 删除数据失败");
        } finally {
            JDBCUtils.getInstance().closeConnection(conn, ps, null);
        }
        System.out.println("数据删除成功！");
    }

    @Override
    public Student findById(int id) throws SQLException {
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        Student s = null;
        String sql = "select * from student where id=?";
        try {
            conn = JDBCUtils.getInstance().getConnection();
            ps = conn.prepareStatement(sql);
            ps.setInt(1, id);
            rs = ps.executeQuery();
            if (rs.next()) {
                s = new Student();
                s.id = id;
                s.name = rs.getString("name");
                s.age = rs.getInt("age");
                s.sex = rs.getString("sex");
                s.tel = rs.getString("tel");
            }
        } catch (Exception e) {
            e.printStackTrace();
            throw new SQLException("根据ID查询数据失败");
        } finally {
            JDBCUtils.getInstance().closeConnection(conn, ps, rs);
        }
        System.out.println("数据查询成功！");
        return s;
    }

    @Override
    public List<Student> findAll() throws SQLException {
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        Student s;
        List<Student> students = new ArrayList<Student>();
        String sql = "select * from student";
        try {
            conn = JDBCUtils.getInstance().getConnection();
            ps = conn.prepareStatement(sql);
            rs = ps.executeQuery();
            while (rs.next()) {
                s = new Student();
                s.id = rs.getInt("id");
                s.name = rs.getString("name");
                s.age = rs.getInt("age");
                s.sex = rs.getString("sex");
                s.tel = rs.getString("tel");
                students.add(s);
            }
        } catch (Exception e) {
            e.printStackTrace();
            throw new SQLException("查询所有数据失败");
        } finally {
            JDBCUtils.getInstance().closeConnection(conn, ps, rs);
        }
        System.out.println("数据查询成功！");
        return students;
    }
}

编写访问查询接口。

package com.tandong.testjavaweb.controller;

import com.tandong.testjavaweb.dao.StudentsDaoImpl;
import com.tandong.testjavaweb.entity.Student;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

/**
 * 注意@RestController用于写接口
 *
 * @Controller 用于写页面跳转
 */
@RestController
//@Controller
@SpringBootApplication
@RequestMapping("/student")
public class StudentController {
    @Autowired
    StudentsDaoImpl studentsDao;

    /**
     * ResopnseBody如果返回的是Object，会把返回结果转为Json格式输出
     *
     * @param userName
     * @return
     */
    @ResponseBody
    @RequestMapping(value = "/getUserName", method = RequestMethod.GET)
    public Object getUserNameGet(@RequestParam(value = "name") String userName) {
        return userName;
    }

    @RequestMapping(value = "/getName", method = RequestMethod.GET)
    public String getName(@RequestParam(value = "name") String name) {
        return "Hello " + name;
    }

    @RequestMapping(value = "/addStudent", method = RequestMethod.GET)
    public String listUser() {
        Student student = new Student();
        student.setAge(12);
        student.setName("学生");
        student.setSex("女");
        student.setTel("13333333333");
        try {
            studentsDao.add(student);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return "插入成功";
    }

    @RequestMapping(value = "/list", method = RequestMethod.GET)
    public Object getLists() {
        List<Student> userList = null;
        try {
            userList = studentsDao.findAll();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return userList;
    }
}

其中@Autowired是自动装配的注解。

好了，我们运行下。

访问：http://localhost:8082/student/addStudent，插入一条数据。

多插入几条，我们再访问：http://localhost:8082/student/list，查询数据。

附带下mysql常用命令：

删除mysql服务命令：sc delete mysql，或mysqld --remove

接下来再看下Spring-Boot-jdbc使用方式，也就是JDBCTemplate。

pom.xml导包：

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

基于原来的StudentImpl，我们修改下：

package com.tandong.testjavaweb.dao;

import com.tandong.testjavaweb.entity.Student;
import com.tandong.testjavaweb.utils.JDBCUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Service;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

@Service
public class StudentsDaoImpl implements StudentsDao {
    @Autowired
    JdbcTemplate jdbcTemplate;

    @Override
    public void add(Student s) throws SQLException {
        jdbcTemplate.update("insert into student(id,name,sex,age,tel)values(?,?,?,?,?)", s.getId()
                , s.getName(), s.getSex(), s.getAge(), s.getTel());
    }

    @Override
    public void update(Student s) throws SQLException {
        jdbcTemplate.update("UPDATE  student SET name=? ,sex=?,age=?,tel=? WHERE id=?",
                s.getName(), s.getSex(), s.getAge(), s.getTel(), s.getId());
    }

    @Override
    public void delete(int id) throws SQLException {
        jdbcTemplate.update("DELETE from TABLE student where id=?", id);
    }

    @Override
    public Student findById(int id) throws SQLException {
        List<Student> list = jdbcTemplate.query("select * from student where id = ?", new Object[]{id}, new BeanPropertyRowMapper(Student.class));
        if (list != null && list.size() > 0) {
            Student student = list.get(0);
            return student;
        } else {
            return null;
        }
    }

    @Override
    public List<Student> findAll() throws SQLException {
        List<Student> list = jdbcTemplate.query("select * from student", new Object[]{}, new BeanPropertyRowMapper(Student.class));
        if (list != null && list.size() > 0) {
            return list;
        } else {
            return null;
        }
    }
}

StudentController不需要修改，重新编译运行，这样就可以达到一样的效果了。

完整项目Github地址：https://github.com/jaychou2012/Spring-Boot-Web

Spring Boot数据库操作之基本的JDBC访问和JDBCTemplate使用

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