Java 基于 mysql-connector-java 编写一个 JDBC 工具类

用到的 jar 包

jar包地址:

mysql-connector-java-5.1.47.jar

junit-4.13.jar

Maven:


<dependency>
  <groupId>mysqlgroupId>
  <artifactId>mysql-connector-javaartifactId>
  <version>5.1.47version>
dependency>

<dependency>
  <groupId>junitgroupId>
  <artifactId>junitartifactId>
  <version>4.13version>
dependency>

MySQL 配置文件

db.properties,这个配置文件在 BaseDao.java 会去读取

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/smbms?useUnicode=true&characterEncoding=UTF-8
username=root
password=123456

BaseDao.java 公共类

通过读取 db.properties 的配置信息连接 MySQL,也可以直接在 static 静态代码块里面写死你的 mysql 配置信息

package com.pro.dao;

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

// 操作数据库公共类
public class BaseDao {
    private static String driver;
    private static String url;
    private static String username;
    private static String password;

    // 静态代码块类一加载就已经初始化了
    static {
        Properties properties = new Properties();

        // 通过类加载器加载对应的资源
        InputStream is = BaseDao.class.getResourceAsStream("/db.properties");
        System.out.println("资源路径 --> " + is);

        try {
            properties.load(is);
        } catch (IOException e) {
            e.printStackTrace();
        }

        // 读取数据, 初始化 mysql 配置信息
        driver = properties.getProperty("driver");
        url = properties.getProperty("url");
        username = properties.getProperty("username");
        password = properties.getProperty("password");
    }

    // 获取连接数据库对象
    public static Connection getConnection() {
        Connection connection = null;

        try {
            // 加载驱动
            Class.forName(driver);
            // 获取数据库对象
            connection = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return connection;
    }

    // 查询公共方法
    public static ResultSet execute(Connection connection, PreparedStatement preparedStatement, ResultSet resultSet, String sql, Object[] params) throws SQLException {
        // 预编译SQL
        preparedStatement = connection.prepareStatement(sql);

        // 添加参数
        for (int i = 0; i < params.length; i++) {
            preparedStatement.setObject(i + 1, params[i]);
        }

        // 执行sql
        resultSet = preparedStatement.executeQuery();

        return resultSet;
    }

    // 增删改公共方法
    public static int execute(Connection connection, PreparedStatement preparedStatement, String sql, Object[] params) throws SQLException {
        int updateRows = 0;
        // 预编译SQL
        preparedStatement = connection.prepareStatement(sql);

        // 添加参数
        for (int i = 0; i < params.length; i++) {
            preparedStatement.setObject(i + 1, params[i]);
        }

        // 执行sql
        updateRows = preparedStatement.executeUpdate();

        return updateRows;
    }

    // 关闭资源公共方法
    public static boolean closeResource(ResultSet resultSet, PreparedStatement preparedStatement, Connection connection) {
        boolean flag = true;

        if (resultSet != null) {
            try {
                // 关闭资源
                resultSet.close();
                // GC 回收
                resultSet = null;
            } catch (SQLException throwables) {
                throwables.printStackTrace();
                flag = false;
            }
        }


        if (preparedStatement != null) {
            try {
                // 关闭资源
                preparedStatement.close();
                // GC 回收
                preparedStatement = null;
            } catch (SQLException throwables) {
                throwables.printStackTrace();
                flag = false;
            }
        }

        if (connection != null) {
            try {
                // 关闭资源
                connection.close();
                // GC 回收
                connection = null;
            } catch (SQLException throwables) {
                throwables.printStackTrace();
                flag = false;
            }
        }

        return flag;
    }
}

测试使用

使用 junit 进行单元测试,也可以直接放到 main 方法中去执行测试

import org.junit.Test;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class Test {
	@Test
    public void test() {
        Connection connection = BaseDao.getConnection();
        PreparedStatement pstm = null;
        ResultSet res = null;

        // SQL
        String sql = "select * from smbms_user";
        // 参数
        Object[] params = {};

        try {
            // 执行SQL
            res = BaseDao.execute(connection, pstm, res, sql, params);

            // 打印参数
            while (res.next()) {
                System.out.println(res.getString("userName"));
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }
}

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