• Java JDBC

    一、JDBC 由来和定义

    Java 数据库连接，（Java Database Connectivity，简称 JDBC）是 Java 语言中用来规范客户端程序如何来访问数据库的应用程序接口，提供了诸如查询和更新数据库中数据的方法。


    二、JDBC 的使用

    package com.google.study.jdbc;

import com.mysql.jdbc.*;

import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;

public class JdbcDemo {
   public static final String URL = "jdbc:mysql://localhost:3306/student";
   public static final String USER = "root";
   public static final String PASSWORD = "xiaoshi";

   public static void main(String[] args) throws SQLException, ClassNotFoundException {
       // 1.加载驱动程序「给布料厂商打电话，说明自己是mysql公司，需要布料」
       Class.forName("com.mysql.jdbc.Driver");
       // 2.获得数据库连接「告诉送货员，具体走什么路线送货」
       Connection connection = (Connection) DriverManager.getConnection(URL, USER, PASSWORD);
       // 3.获取数据库操作对象「声明货物送到了，开始卸货」
       Statement statement = (Statement) connection.createStatement();

       ResultSet resultSet = statement.executeQuery("SELECT * FROM info");
       while (resultSet.next()) {
           int id = resultSet.getInt(2);
           String name = resultSet.getString(1);
           int age = resultSet.getInt(3);
           System.out.println("id:" + id + ",name:" + name + ",age:" + age);
       }

       // 4.关闭数据库连接
       statement.close();
       connection.close();
   }
}


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    三、代码规范

    package com.google.study.jdbc;

import com.mysql.jdbc.*;

import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;

public class JdbcDemo {
    public static final String URL = "jdbc:mysql://localhost:3306/student";
    public static final String USER = "root";
    public static final String PASSWORD = "xiaoshi";

    public static Connection connection;
    public static Statement statement;
    public static ResultSet resultSet;

    public static void main(String[] args) throws SQLException, ClassNotFoundException {
        try {
            // 1.加载驱动程序「给布料厂商打电话，说明自己是mysql公司，需要布料」
            Class.forName("com.mysql.jdbc.Driver");
            // 2.获得数据库连接「告诉送货员，具体走什么路线送货」
            connection = (Connection) DriverManager.getConnection(URL, USER, PASSWORD);
            // 3.获取数据库操作对象「声明货物送到了，开始卸货」
            statement = (Statement) connection.createStatement();

            resultSet = statement.executeQuery("SELECT * FROM info");

            while (resultSet.next()) {
                int id = resultSet.getInt(2);
                String name = resultSet.getString(1);
                int age = resultSet.getInt(3);
                System.out.println("id:" + id + ",name:" + name + ",age:" + age);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try{
                statement.close();
                connection.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}


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    四、封装 JDBCUtils

    新建配置文件 db.properties

    url=jdbc:mysql://localhost:3306/student
user=root
password=xiaoshi
driver=com.jdbc.mysql.Driver

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    新建 JDBC 封装类 JDBCUtils

    package com.google.study.jdbc;

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

public class JDBCUtils {
    private static String driver;
    private static String url;
    private static String user;
    private static String password;

    // 静态代码块，预先读取配置文件的配置项，做预处理
    static {
        try {
            // 获取当前类加载器
            ClassLoader classLoader=JDBCUtils.class.getClassLoader();
            // 通过当前累加载器方法获得 文件db.properties的一个输入流
            InputStream inputStream = classLoader.getSystemResourceAsStream("db.properties");
            //创建一个Properties 对象
            Properties properties = new Properties();
            // 读取配置文件
            properties.load(inputStream);

            driver = properties.getProperty("driver");
            url = properties.getProperty("url");
            user = properties.getProperty("user");
            password = properties.getProperty("password");

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    // 连接方法
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url,user,password);
    }

    // 关闭数据库连接
    public static void close(Connection connection, Statement statement) throws SQLException {
        if (statement != null) {
            statement.close();
        }
        if (connection != null) {
            connection.close();
        }
    }

    public static void close(Connection connection, Statement statement, ResultSet resultSet) throws SQLException {
        if (statement != null) {
            statement.close();
        }
        if (connection != null) {
            connection.close();
        }
        if (resultSet != null) {
            resultSet.close();
        }
    }
}

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    测试封装后的 JDBCUtils 类中的功能

    创建 JdbcDemo 类对数据库进行增删改

    package com.google.study.jdbc;

import com.sun.xml.internal.bind.v2.TODO;
import org.junit.Test;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class JdbcDemo {

    public Connection connection;
    public Statement statement;
    public ResultSet resultSet;

    @Test
    public void insertTest () throws SQLException {
        try {
            connection = JDBCUtils.getConnection();
            statement = connection.createStatement();

            String sqlIns = "INSERT INTO info(name,age) VALUES('insert',18)";
            String sqlDel = "DELETE FROM info WHERE id=4";
            String sqlUpd = "UPDATE info SET name='AA' WHERE id=2";

            // 增
            int resIns = statement.executeUpdate(sqlIns);
            // 删
            int resDel = statement.executeUpdate(sqlDel);
            // 改
            int resUpd = statement.executeUpdate(sqlUpd);

            if (resIns > 0) {
                System.out.println("Insert success!");
            }
            if (resDel > 0) {
                System.out.println("Delete success!");
            }
            if (resUpd > 0) {
                System.out.println("Update success!");
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCUtils.close(connection,statement);
        }
    }
}


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    五、字符编码问题

    上述封装类中插入“中文，符号”等会遇到乱码问题

    • 更新 db.prooerties 配置文件：
    url=jdbc:mysql://localhost:3306/student?characterEncoding=utf8
user=root
password=xiaoshi
driver=com.jdbc.mysql.Driver

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    六、管理系统

    1. 封装 JDBCUtils 数据库配置类
    package com.google.study.student;

import com.google.study.jdbc.JDBCUtils;

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

public class JdbcUnitl {
    private static String driver;
    private static String url;
    private static String user;
    private static String password;

    static {
        try {
            ClassLoader classLoader = JDBCUtils.class.getClassLoader();
            InputStream inputStream = classLoader.getResourceAsStream("db.properties");
            Properties properties = new Properties();
            properties.load(inputStream);

            driver = properties.getProperty("dricer");
            url = properties.getProperty("url");
            user = properties.getProperty("user");
            password = properties.getProperty("password");

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url,user,password);
    }

    public static void close (Connection connection, Statement statement) throws SQLException {
        if (statement != null) {
            statement.close();
        }
        if (connection != null) {
            connection.close();
        }
    }

    public static void close (Connection connection, Statement statement, ResultSet resultSet) throws SQLException {
        if (statement != null) {
            statement.close();
        }
        if (connection != null) {
            connection.close();
        }
        if (resultSet != null) {
            resultSet.close();
        }
    }
}


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    1. 封装 Student 学生信息类
    package com.google.study.student;

import java.rmi.StubNotFoundException;

public class Student {
    public static int id;
    public static String name;
    public static int age;

    public Student() {

    }

    public Student(int id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

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

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

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

    public String getName() {
        return this.name;
    }

    public int getId () {
        return this.id;
    }

    public int getAge() {
        return this.age;
    }

    public String toString() {
        return "id:" + this.id + "|" + "name:" + this.name + "|" + "age:" + this.age;
    }
}


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    1. 封装 StudentServer 数据库操作类
    package com.google.study.student;

import com.google.study.jdbc.JDBCUtils;

import java.sql.*;
import java.util.ArrayList;
import java.util.Scanner;

public class StudentServer {
    public static Connection connection;
    public static PreparedStatement preparedStatement;
    public static ResultSet resultSet;
    public static Scanner scanner = new Scanner(System.in);

    public static ArrayList<Student> selectAll() throws SQLException {

        ArrayList<Student> arrayList = new ArrayList<>();

        try {
            connection = JdbcUnitl.getConnection();

            String sql = "SELECT * FROM info";

            preparedStatement = connection.prepareStatement(sql);

            resultSet = preparedStatement.executeQuery();

        while (resultSet.next()) {
                arrayList.add(new Student(resultSet.getInt(1), resultSet.getString(2), resultSet.getInt(3)));
            }
            return arrayList;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                JDBCUtils.close(connection, preparedStatement);
                scanner.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return arrayList;
    }

    public static Student selectById(int id) {
        Student student = new Student();
        try {
            connection = JdbcUnitl.getConnection();

            String sql = "SELECT * FROM info WHERE id=?";

            preparedStatement = connection.prepareStatement(sql);

            preparedStatement.setInt(1,id);

            resultSet = preparedStatement.executeQuery();

            while (resultSet.next()) {
                student.setId(resultSet.getInt(1));
                student.setName(resultSet.getString(2));
                student.setAge(resultSet.getInt(3));
            }
            return student;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                JDBCUtils.close(connection, preparedStatement);
                scanner.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return student;
    }

    public static boolean update(int id, String name, int age) {

        try {
            connection = JdbcUnitl.getConnection();

            String sql = "UPDATE info SET name=?,age=? WHERE id=?";

            preparedStatement = connection.prepareStatement(sql);

            preparedStatement.setInt(3,id);
            preparedStatement.setString(1,name);
            preparedStatement.setInt(2,age);

            int resultSet = preparedStatement.executeUpdate();

            if (resultSet > 0)
                return true;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                JDBCUtils.close(connection, preparedStatement);
                scanner.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return false;
    }

    public static boolean delete(int id) {

        try {
            connection = JdbcUnitl.getConnection();

            String sql = "DELETE FROM info WHERE id=?";

            preparedStatement = connection.prepareStatement(sql);

            preparedStatement.setInt(1,id);

            int resultSet = preparedStatement.executeUpdate();

            if (resultSet > 0)
                return true;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                JDBCUtils.close(connection, preparedStatement);
                scanner.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return false;
    }


    public static boolean add(String name,int age) {

        try {
            connection = JdbcUnitl.getConnection();

            String sql = "INSERT INTO info(name,age) VALUES(?,?)";

            preparedStatement = connection.prepareStatement(sql);

            preparedStatement.setString(1,name);
            preparedStatement.setInt(2,age);

            int resultSet = preparedStatement.executeUpdate();

            if (resultSet > 0)
                return true;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                JDBCUtils.close(connection, preparedStatement);
                scanner.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return false;
    }
}


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    1. 封装 RunApplication 程序启动类
    package com.google.study.student;

import java.sql.SQLException;
import java.util.Scanner;

public class RunApplication {

    static Scanner sc = new Scanner(System.in);

    public static void main(String[] args) throws SQLException {
        init();
    }

    public static void init() throws SQLException {
        System.out.println("-----欢迎进入信息管理系统-----");

        System.out.println(
                "----------1.selectAll------\n" +
                        "----------2.selectById-----\n" +
                        "----------3.update---------\n" +
                        "----------4.delete---------\n" +
                        "----------5.add------------\n" +
                        "----------6.quit-----------");

        System.out.println("-----选择序号进行系统操作-----");

        functionService();
    }

    public static void functionService() throws SQLException {
        String usingNext = sc.next();
        switch (usingNext) {
            case "1":
                System.out.println(StudentServer.selectAll());
                break;

            case "2":
                System.out.println("请输入要查询学生的id：");
                System.out.println(StudentServer.selectById(sc.nextInt()));
                break;

            case "3":
                System.out.println("请输入要更新学生的id，name，age：");
                System.out.println(StudentServer.update(sc.nextInt(), sc.next(), sc.nextInt()));
                break;

            case "4":
                System.out.println("请输入要删除学生的id：");
                System.out.println(StudentServer.delete(sc.nextInt()));
                break;

            case "5":
                System.out.println("请输入要添加学生的姓名，年龄：");
                System.out.println(StudentServer.add(sc.next(), sc.nextInt()));
                break;

            case "6":
                System.out.println("系统退出成功");
                System.exit(0);
                break;

            default:
                break;
        }
    }
}


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  • 原文地址：https://blog.csdn.net/weixin_47050177/article/details/126813969