JDBC基础入门使用

Class.forName("com.mysql.cj.jdbc.Driver");
conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/test_demo?useSSL=false&serverTimezone=UTC","root","password");
// 字符串连接参数
// jdbc:mysql://localhost:3306/jdbcboot?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC&useSSL=true

<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.16</version>
</dependency>

package com.weiyi.Jdbc;

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

import com.mysql.cj.jdbc.result.ResultSetMetaData;

public class Demo1 {
  @SuppressWarnings("unused")
  public static void main(String[] args) throws SQLException {
    
    //JDB连接标准文档
    Connection conn = null;
    Statement st = null;
    ResultSet rs = null;
    try {
      //Step 1.驱动注册(实际上不建议采用此类方法加载驱动-他会注册两次)
      DriverManager.registerDriver(new com.mysql.cj.jdbc.Driver());
      
      //Step 2.构建连接字符串和建立链接
      String urlFormat = "jdbc:mysql://%s:%d/%s?useUnicode=true&characterEncoding=UTF-8";
      String connectionUrl = String.format(urlFormat, "113.xx.xx.xxx", 3306, "Demo");
      conn = DriverManager.getConnection(connectionUrl, "root", "WeiyiGeek");
      
      //Step 3.创建statement
      st = conn.createStatement();
      
    
      //Step 4.构建SQL语句以及执行语句
      String sql = "SELECT ID AS '序号',LastName AS '名称' FROM Persons WHERE ID <> 102";
      rs = st.executeQuery(sql);
      
      //Step 5.遍历数据库
      while(rs.next()){
        //System.out.println("ID: " + rs.getInt("ID") + " , LastName = " + rs.getString("LastName"));  //注意此处使用别名的时候(不能采用字段名进行获取数据库返回的值);
        System.out.println("ID: " + rs.getInt("序号") + " , LastName = " + rs.getString("名称"));
      }
      
      //Step 6.获取元数据metadate
      ResultSetMetaData rsmd = (ResultSetMetaData) rs.getMetaData();
      int numCols = rsmd.getColumnCount(); //获取列元素数据量
      int count = 1;
      while(count <= numCols) {
        System.out.printf("第 %d 列： 列名: %s , AS别名: %s , 类型:%s n",count, rsmd.getColumnName(count), rsmd.getColumnLabel(count), rsmd.getColumnType(count));
        count++;
      }
    
    } catch (SQLException sqlEx) {
      // TODO: handle exception
      sqlEx.printStackTrace();
    } finally {
      //Step 7.释放资源(非常重要) - 从后往前
      System.out.println("Start-释放资源中");
      //结果集对象
      try {
        if(rs != null)
          rs.close();
      } catch (SQLException e) {
        e.printStackTrace();
      } finally {
        rs = null;
      }
      
      //statement对象
      try {
        if(st != null)
          st.close();
      } catch (SQLException e) {
        e.printStackTrace();
      } finally {
        st = null;
      }
      
      //数据库连接对象
      try {
        if(conn != null)
          conn.close();
      } catch (SQLException e) {
        e.printStackTrace();
      } finally {
        conn = null;
      }
      System.out.println("Successful-资源释放完成!");

      //当然您也可以采用自己封装后的JDBC工具类(非常注意释放的顺序)
      //JDBCUtil.release(conn,st,rs);
    }
  }
}

ID: 100 , LastName = WeiyiGeek
ID: 101 , LastName = Admin
ID: 103 , LastName = Weiyi
ID: 104 , LastName = Young
ID: 105 , LastName = bb204949-3283-11ea-b468-0242ac120002
第 1 列： 列名: ID , AS别名: 序号 , 类型:4 
第 2 列： 列名: LastName , AS别名: 名称 , 类型:12 
Start-释放资源中
Successful-资源释放完成!

//该包下的类可以通过静态类 类.方法()进行调用
//该包下的类可以通过静态类 类.方法()进行调用
package com.weiyi.Jdbc;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JDBCUtil {
  static String connUrl = "jdbc:mysql://%s:%d/%s?useUnicode=true&characterEncoding=UTF-8";
  static String connIp = "13.62.17.23";
  static int connPort = 9301;
  static String conndatabase = "Demo";
  static String driverClass = null;  //使用的时候添加
  static String url = null;
  static String user = null;
  static String pass = null;
  
  //静态代码块,加载类的时候执行
  static {
    try {
      //Step1.创建一个属性配置对象
      Properties prop = new Properties();
    
      //Step2.打开配置文件
      //InputStream ins = new FileInputStream("jdbc.properties");
      InputStream ins = Demo3.class.getClassLoader().getResourceAsStream("jdbc.properties");

      //Step3.导入输入流
      prop.load(ins);
    
      //Step4.属性读取		
      driverClass = prop.getProperty("jdbc.driverClassName");
      url = String.format(prop.getProperty("jdbc.url"),connIp,connPort,conndatabase);
      user = prop.getProperty("jdbc.username");
      pass = prop.getProperty("jdbc.password");
    } catch (Exception e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } finally {
      System.out.println("Properties配置已经加载!");
    }
  }
  
  public JDBCUtil() {
    super();
    // TODO Auto-generated constructor stub
  }
  public JDBCUtil(String ip,int port,String database) {
    connIp = ip;
    connPort = port;
    conndatabase = database;
  }

  //注册工具方法
  /**
	 * 驱动注册和建立链接
	 * @param user
	 * @param password
	 * @return Connection
	 * @throws SQLException
	 */
  public static Connection getConn() throws SQLException {
    Connection conn = null;
    System.out.println("连接字符串:" + url);
    try {
      //防止驱动二次注册自动注册驱动与建立连接			
      conn = DriverManager.getConnection(url, user, pass);
    } catch (SQLException e) {
      e.printStackTrace();
    }
    return conn;	
  }
  
  
  /**
	 * 释放工具类
	 * @param conn
	 * @param st
	 * @param rs
	 */
  
  // 注意点:导包需要查看是哪一个包的返回值
  public static void release(Connection conn, Statement st, ResultSet rs) {
    //注意点:关闭的顺序
    closeRs(rs);
    closeSt(st);
    closeConn(conn);
    System.out.println("END-资源释放完成!");
  }

  //私有静态方法-释放查询结果集
  private static void closeRs(ResultSet rs) {
    try {
      if(rs != null)
        rs.close();
    } catch (SQLException e) {
      e.printStackTrace();
    } finally {
      rs = null;
    }
  }
  
  //私有静态方法-释放statement对象
  private static void closeSt(Statement st) {
    try {
      if(st != null)
        st.close();
    } catch (SQLException e) {
      e.printStackTrace();
    } finally {
      st = null;
    }
  }
  
  //私有静态方法-
  private static void closeConn(Connection conn) {
    try {
      if(conn != null)
        conn.close();
    } catch (SQLException e) {
      e.printStackTrace();
    } finally {
      conn = null;
    }
  }
}

driverClass=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/student??useUnicode=true&characterEncoding=UTF-8
name=root
password=root

//使用类加载器去读取src底下的资源文件后面在servlet  
//对应文件位于src目录底下在编译打包后存在在bin目录同层中,使用getClassLoader()在加载字节码文件时候顺便也加载了我们制定的资源文件
//InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");

package com.weiyi.Jdbc;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Properties;

import com.mysql.cj.jdbc.result.ResultSetMetaData;

import javafx.scene.control.SplitPane.Divider;

public class Demo3 {
  /**
	 * JDBC 连接参数采用 Properties配置文件进行导入
	 * @param args
	 */
   //使用静态代码块读取属性(当类加载的时候执行)
  static String driverClass = null;
  static String url = null;
  static String user = null;
  static String pass = null;
  
  static {
    try {
      //Step1.创建一个属性配置对象
      Properties prop = new Properties();
    
      //Step2.打开配置文件
      //InputStream ins = new FileInputStream("jdbc.properties"); //在根目录中可以采用这种方式
      InputStream ins = Demo3.class.getClassLoader().getResourceAsStream("jdbc.properties");

      //Step3.导入输入流
      prop.load(ins);
    
      //Step4.属性读取		
      driverClass = prop.getProperty("jdbc.driverClassName");
      url = prop.getProperty("jdbc.url");
      user = prop.getProperty("jdbc.username");
      pass = prop.getProperty("jdbc.password");
    } catch (Exception e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } finally {
      System.out.println("- #ProPerties配置文件读取完成!");
    }
    
  }
  
  public static void main(String[] args) {
    //JDB连接标准文档
    Connection conn = null;
    Statement st = null;
    ResultSet rs = null;
    
    try {
      //1.驱动注册
      Class.forName(driverClass); //实际上这句话都可以免了在JDBC4.0之后他会自动在jdbc的数据库驱动jar包中元数据进行查看
      //2.建立连接
      conn = DriverManager.getConnection(url, user, pass);
      //3.建立statement对象
      st = conn.createStatement();
      //4.构建SQL语句并且执行
      rs = st.executeQuery("SELECT * FROM Persons WHERE (ID = 100)"); //Retrieve
      //5.获取数据
      ResultSetMetaData rsmd = (ResultSetMetaData) rs.getMetaData(); //获取源数据
      int len = rsmd.getColumnCount();  //字段梳理
      int count = 1;
      while(count <= len) {
        System.out.print(rsmd.getColumnName(count) + " | ");
        count++;
      }
      System.out.println("");
      while (rs.next()) {
        System.out.println(rs.getInt("ID") + "| " + rs.getString("LastName"));
      }
      
      //6.数据库的CRUD;
      String sql = "INSERT INTO Persons VALUE (NULL,'Weiyi')";  //主要Primary Key 插入主键的时候可以用null代替 
      int result = st.executeUpdate(sql); //该方法主要执行 INSERT, UPDATE or DELETE 等语句，返回影响的行数
      //如果返回值大于0则表明操作成功,否则失败;
      if(result > 0) {
        System.out.println("插入成功 : "+ sql);
      }else {
        System.out.println("插入失败");
      }
      
      // U :
      String sqlUpdate = "UPDATE Persons SET LastName = 'Whoami' WHERE ID = 100";
      result = st.executeUpdate(sqlUpdate);
      if(result > 0) {
        System.out.println("更新成功 : " + sqlUpdate);
      }else {
        System.out.println("更新失败");
      }
        
      // D:
      String sqlDelete = "DELETE FROM Persons WHERE LastName = 'Weiyi'";
      result = st.executeUpdate(sqlDelete);
      if( result > 0) {
        System.out.println("删除成功 : " + sqlDelete);
      }else {
        System.out.println("删除失败");
      }
          
    } catch (SQLException e) {
      // TODO: handle exception
    } finally {
      //End.释放资源
      JDBCUtil.release(conn, st, rs);
    }
  }
}

- #ProPerties配置文件读取完成!
查询成功 : SELECT * FROM Persons WHERE (ID = 100)
ID | LastName | 
100| Whoami
插入成功 : INSERT INTO Persons VALUE (NULL,'Weiyi')
更新成功 : UPDATE Persons SET LastName = 'Whoami' WHERE ID = 100
删除成功 : DELETE FROM Persons WHERE LastName = 'Weiyi'
读取完成
END-资源释放完成!

package com.weiyi.Test;

import java.util.Date;
import org.junit.Test;

/**
 * 使用junit进行单元测试
 * @author WeiyiGeek
 */
public class MainTest {
  
  //单元测试需要测试的方法
  @Test
  public void testPrint() {
    Date date = new Date();
    System.out.println("当前时间:" + date.toGMTString());
  }
}

-- (1) 建立一个测试的表
CREATE TABLE user_log (
  id INT NOT NULL PRIMARY KEY AUTO_INCREMENT COMMENT '序号',
  userLogin VARCHAR(255) NOT NULL COMMENT '登陆名称',
  userPass VARCHAR(255) NOT NULL COMMENT '登陆密码',
  loginTime DATETIME NOT NULL DEFAULT NOW()  COMMENT '登陆时间'
);

-- (2) 数据插入
INSERT INTO user_log(id,userLogin) VALUES (NULL,'WeiyiGeek');

// 1.接口
package com.weiyi.dao;
public interface userDao {
  /**
	 * Dao模型-接口定义操作数据库的方法
	 */
  void findAll();
}


// 2.实现接口
package com.weiyi.dao.impl;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import com.weiyi.Jdbc.JDBCUtil;
import com.weiyi.dao.userDao;
public class userDaoImpl implements userDao{
  //JDBC连接标准文档
  Connection conn = null;
  Statement st = null;
  ResultSet rs = null;
  
  @Override
  public void findAll() {
    try {
      //1.驱动加载和建立链接
      conn = JDBCUtil.getConn();
      //2.建立流对象statement
      st = conn.createStatement();
      //3.构建执行SQL语句 （这里的SQL语句是拼接的容易导致安全问题）
      rs = st.executeQuery("SELECT * FROM user_log");
      while(rs.next()){
        System.out.println(rs.getInt("id") + " " + rs.getString("userLogin") + " " + rs.getDate("loginTime"));
      }
    } catch (Exception e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } finally {
      JDBCUtil.release(conn, st, rs);
    }
  }
}


// 3.调用接口
package com.weiyi.Jdbc;
import com.weiyi.dao.userDao;
import com.weiyi.dao.impl.userDaoImpl;
/**
 * 调用 dao 模型 实现的接口方法
 * @author WeiyiGeek
 */
public class Demo4 {
  //注意:这里测试也可以采用Junit单元测试
  public static void main(String[] args) {
    //Step1.父类指向子类实现的接口
    userDao dao = new userDaoImpl();
    //Step2.直接调用其方法不用管具体的实现
    dao.findAll();
  }
}

Properties配置已经加载!
连接字符串:jdbc:mysql://11.62.17.20:3001/Demo?useUnicode=true&characterEncoding=UTF-8
1 WeiyiGeek 2020-01-14
END-资源释放完成!

String sql = "insert into t_user values(null , ? , ?)";
ps = conn.prepareStatement(sql);
//给占位符赋值 从左到右数过来，1 代表第一个问号， 永远你是1开始。
ps.setString(1, userName);

// dao 模型接口
package com.weiyi.dao;
public interface userDao {
  /** Dao模型-接口定义操作数据库的方法*/
  void psLogin(String user,String pass,int x);
  void psInsert(String user,String pass);
  void psUpdate(String user,int id);
  void psDelete(String user,String pass);
}


// dao 模型接口具体实现
package com.weiyi.dao.impl;

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

import com.weiyi.Jdbc.JDBCUtil;
import com.weiyi.dao.userDao;

public class userDaoImpl implements userDao{
  //JDBC连接标准文档
  Connection conn = null;
  Statement st = null;
  ResultSet rs = null;
  

  /***  创建PreparedStatement预处理对象 */
  @Override
  public void psLogin(String user,String pass, int x) {
    try {
      //1.载入数据库驱动建立链接
      conn = JDBCUtil.getConn();
      //2.构建SQL语句以及预处理SQL语句
      String sql = "SELECT * FROM user_log WHERE userLogin = ? AND userPass = md5(?) AND id = ?";  //? 占位符合后面会将绑定的参数进行格式化后传入
      PreparedStatement ps = conn.prepareStatement(sql); //关键点1:对我们的SQL语句进行预处理如果SQL语法错误的将不能通过解析
      ps.setString(1, user);  //关键点2:进行传入参数的位置开始绑定从,1代表第一个问号,2同理;
      ps.setString(2, pass);  //关键点3:注意传入的类型是可以根据需要来设置的;
      ps.setInt(3, x);
      //3.执行预处理好的的对象
      rs = ps.executeQuery();
      if(rs.next()) {
        System.out.println("登陆成功!");
        System.out.println("欢迎您" + rs.getString("userLogin") + "管理员, 注册时间: " + rs.getTimestamp("loginTime"));
      } else {
        System.out.println("登陆失败");
      }
    } catch (Exception e) {
      // TODO: handle exception
      e.printStackTrace();
    } finally {
      JDBCUtil.release(conn, st, rs);
    }
  }
  
  
  @Override
  public void psInsert(String user, String pass) {
    PreparedStatement ps = null;
    try {
      conn = JDBCUtil.getConn();
      String sql = "INSERT INTO user_log(userLogin,userPass) VALUES (?,md5(?))";
      ps = conn.prepareStatement(sql);
      ps.setString(1, user);
      ps.setString(2, pass);
      int result = ps.executeUpdate();
      if(result > 0) {
        System.out.println("成功添加" + user + "用户!");
      }else {
        System.out.println("用户注册失败!");
      }
    } catch (SQLException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } finally {
      JDBCUtil.release(conn, ps);
    }
  }

  @Override
  public void psUpdate(String user, int id) {
    PreparedStatement ps = null;
    try {
      conn = JDBCUtil.getConn();
      String sql = "UPDATE user_log SET userLogin = ? WHERE id = ?";
      ps = conn.prepareStatement(sql);
      ps.setString(1, user);
      ps.setInt(2, id);
      int result = ps.executeUpdate();
      if(result>0) {
        System.out.println("更新用户ID = " + id + ", 为 " + user+"用户成功!");
      }else {
        System.out.println("更新失败");
      }
    } catch (SQLException e) {
      // TODO: handle exception
      e.printStackTrace();
    } finally {
      JDBCUtil.release(conn, ps);
    }	
  }

  @Override
  public void psDelete(String user, String pass)  {
    PreparedStatement ps = null;
    try {
      conn = JDBCUtil.getConn();
      String sql = "DELETE FROM user_log WHERE userLogin = ? AND userPass = md5(?)";
      ps = conn.prepareStatement(sql);
      ps.setString(1, user);
      ps.setString(2, pass);
      int result = ps.executeUpdate();
      if(result > 0){
        System.out.println("用户 " + user +" 删除成功!");
      }else {
        System.out.println("删除失败");
      }
      
    } catch (SQLException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } finally {
      JDBCUtil.release(conn, ps);
    }
  }
}

Properties配置已经加载!
连接字符串:jdbc:mysql://127.0.0.1:3301/Demo?useUnicode=true&characterEncoding=UTF-8
登陆成功!
欢迎您WeiyiGeek管理员, 注册时间: 2020-01-14 12:42:20.0
更新用户ID = 2, 为 Admin用户成功!
用户 Admin 删除成功!
END-资源释放完成!

public interface ResultSetHandler<T> {
  /**
	 * @用户进行接口实现类对象(实现获取查询后的数据按照调用者的意愿进行封装)
	 * @param rs
	 * @return
	 */
  T sethandler(ResultSet rs);
}

package top.weiyigeek.Util;

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

/**
 * 
 * @Desc: 扩充JDBC自定义连接数据库，通用方法执行增删改查
 * @author WeiyiGeek
 * @CreatTime 下午9:51:05
 */
public class DBUtilTools {
  /**
	 * @Desc: 通用方法进行 插入 删除 与 更新 (DML)
	 * @param sql : INSERT INTO / DELETE FROM / UPDATE
	 * @param args : 可变参数（重要）
	 * @return 
	 */
  public static int update(String sql,Object...args) {
    int flag = 0;
    Connection conn = null;
    PreparedStatement ps = null;
    try {
      conn = db1.getConn();
      ps = conn.prepareStatement(sql);
      //利用参数元数据获取执行SQL语句中的参数个数（即有几个问号）
      ParameterMetaData metaData = ps.getParameterMetaData();
      int count = metaData.getParameterCount();
      
      //进行SQL执行的参数绑定，因为不知道是什么类型的数据所以都使用setObject来处理
      for(int i = 0; i < count; i++) {
        ps.setObject(i+1, args[i]);
      }
      //执行CURD语句()
      flag = ps.executeUpdate();
      return flag;
    } catch (SQLException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } finally {
      db1.release(conn, ps, null);
    }
    return -1;
  }

  /**
	 * @Desc: 通用方法进行 数据库数据的查询 并让调用者自己实现数据的封装（接口实现类对象）
	 * @param <T>
	 * @param sql
	 * @param handler
	 * @param args
	 * @return
	 */
  public static <T> T query(String sql, ResultSetHandler<T> handler,Object...args) {
    Connection conn = null;
    PreparedStatement ps = null;
    ResultSet rs = null;
    try {
      conn = db1.getConn();
      ps = conn.prepareStatement(sql);
      //利用参数元数据获取执行SQL语句中的参数个数（即有几个问号）
      ParameterMetaData metaData = ps.getParameterMetaData();
      int count = metaData.getParameterCount();
      
      //进行SQL执行的参数绑定，因为不知道是什么类型的数据所以都使用setObject来处理
      for(int i = 0; i < count; i++) {
        ps.setObject(i+1, args[i]);
      }
      
      //执行CURD语句
      rs = ps.executeQuery();
      T t = handler.sethandler(rs);
      return t;
    } catch (SQLException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } finally {
      db1.release(conn, ps, null);
    }
    return null;
  }
}

package top.weiyigeek.DBUtil;

import java.sql.ResultSet;

import top.weiyigeek.Util.DBUtilTools;
import top.weiyigeek.Util.ResultSetHandler;

public class DBUtilToolsDemo2 {

  public static void main(String[] args) {
    //1.测试DML语句
    //int flag = DBUtilTools.update("INSERT INTO account value(null,?,?)", "法外狂徒",50);
    //System.out.println("影响条数:"+flag);
    
    //int flag = DBUtilTools.update("UPDATE account SET name = ?,money = money + ? WHERE id = ?", "法外狂徒",150,4);
    //System.out.println("影响条数:"+flag);
    
    //2.测试QUERY语句(接口实现类对象)
    Account a = DBUtilTools.query("SELECT * FROM account where id = ?", new ResultSetHandler<Account>() {
      @Override
      public Account sethandler(ResultSet rs) {
        // TODO Auto-generated method stub
        Account work = new Account();
        try {
          while(rs.next()) {
            int id = rs.getInt("id");
            String name = rs.getString("name");
            int money = rs.getInt("money");
            work.setId(id);
            work.setName(name);
            work.setMoney(money);
          }
          return work;
        } catch (Exception e) {
          // TODO: handle exception
          e.printStackTrace();
          return null;
        }
      }
      
    }, 4);
    System.out.println(a.toString());
  }
}