连接数据库其他操作

上次提到过可以通过参数的方式将要连接的数据库url、用户名及密码等通过参数的方式传给连接函数，下面给出具体测试代码

package Datacon;

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

import com.mysql.jdbc.Connection;

public class Dataconn {
    public String driver="com.mysql.jdbc.Driver";
    private String url = "jdbc:mysql://127.0.0.1:3306/test";
    private String user ="root";
    private String passwd = "root@2017";
    
    //声明默认连接函数
    public Connection  defDataConn() throws ClassNotFoundException, SQLException{
        
        Connection connDB = null;  //初始化返回null
        //加载驱动类
        try{
        Class.forName(driver);
        }catch(ClassNotFoundException e){
            e.printStackTrace();
            System.out.println("未找到指定类");
        }
        try{
        connDB = (Connection) DriverManager.getConnection(url, user, passwd);
        }catch(SQLException
                e){
            e.printStackTrace();
            System.out.println("数据库连接失败");
        }
        return connDB;
        
    }
    public Connection setConnDB(){
        Connection connDB = null;
        try{
            Class.forName(driver);
            }catch(ClassNotFoundException e){
                e.printStackTrace();
                System.out.println("未找到指定类");
            }
            try{
            connDB = (Connection) DriverManager.getConnection(url, user, passwd);
            }catch(SQLException
                    e){
                e.printStackTrace();
                System.out.println("数据库连接失败");
            }
            System.out.println("===================================================");
            System.out.println("=====================自定义函数========================");
            System.out.println("===================================================");
            return connDB;
        
    }
    public Dataconn(String driver, String url, String user, String passwd) {
        super();
        this.driver = driver;
        this.url = url;
        this.user = user;
        this.passwd = passwd;
    }

}

---

除以上方法连接数据库jdbc还提供通过读取配置文件的方式连接数据库，读取配置文件通过Properties类继承自Hashtable类并且实现了Map接口，使用键值对的形式来保存属性集。需要注意的是配置文件的存放位置为class path目录。

properties配置文件

新建配置文件，通过右击src文件夹选择new-other，选择file类型

选择file类型

输入文件名及扩展名点击保存即可。
点击add添加对应配置文件信息。
添加完成点击保存即可

输入内容

通过Properties类实例化，通过x.load（)方式导入文件内容。如下：

prop.load(this.getClass().getClassLoader().getResourceAsStream("DBConfig.properties"));
读取配置文件详细代码如下：

package Datacon;

import java.io.IOException;
import java.io.InputStream;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

import com.mysql.jdbc.Connection;

public class Dataconn {
    public String driver="com.mysql.jdbc.Driver";
    private String url = "jdbc:mysql://127.0.0.1:3306/test";
    private String user ="root";
    private String passwd = "root@2017";
    
    public Dataconn(){
        
    }
    //声明默认连接函数
    public Connection  defDataConn() throws ClassNotFoundException, SQLException{
        
        Connection connDB = null;  //初始化返回null
        //加载驱动类
        try{
        Class.forName(driver);
        }catch(ClassNotFoundException e){
            e.printStackTrace();
            System.out.println("未找到指定类");
        }
        try{
        connDB = (Connection) DriverManager.getConnection(url, user, passwd);
        }catch(SQLException
                e){
            e.printStackTrace();
            System.out.println("数据库连接失败");
        }
        return connDB;
        
    }
    public Connection setConnDB(){
        Connection connDB = null;
        try{
            Class.forName(driver);
            }catch(ClassNotFoundException e){
                e.printStackTrace();
                System.out.println("未找到指定类");
            }
            try{
            connDB = (Connection) DriverManager.getConnection(url, user, passwd);
            }catch(SQLException
                    e){
                e.printStackTrace();
                System.out.println("数据库连接失败");
            }
            System.out.println("===================================================");
            System.out.println("=====================自定义函数========================");
            System.out.println("===================================================");
            return connDB;
        
    }
    public Dataconn(String driver, String url, String user, String passwd) {
        super();
        this.driver = driver;
        this.url = url;
        this.user = user;
        this.passwd = passwd;
    }
    public Connection openFileconn() throws IOException, ClassNotFoundException, SQLException{
        Connection dataConn = null;
        
        Properties prop = new Properties();
        try{
            prop.load(this.getClass().getClassLoader().getResourceAsStream("DBConfig.properties"));  //读入配置文件 
            this.driver=prop.getProperty("driver"); //获取配置文件中相应键值
            this.url = prop.getProperty("url");
            this.user = prop.getProperty("user");
            this.passwd = prop.getProperty("password");
        }catch(IOException e){
            e.printStackTrace();
        }
        System.out.println("config file :"+this.driver+this.url+this.user+this.passwd);
        try{
            Class.forName(driver);
        }catch(ClassNotFoundException e){
            e.printStackTrace();
            System.out.println("为找到该java驱动");
        }
        try{
        dataConn = (Connection) DriverManager.getConnection(url, user, passwd);
        }catch(SQLException e){
            e.printStackTrace();
            System.out.println("连接失败");
        }
        return dataConn;
    }

}

方法测试代码如下：

package Datacon;

import java.io.IOException;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import javax.swing.plaf.basic.BasicInternalFrameTitlePane.RestoreAction;

import org.junit.Test;

import com.mysql.jdbc.Connection;

public class testRun { 
    
    @Test
    public void runDef() throws ClassNotFoundException, SQLException{
        Dataconn dataconn = new Dataconn();
        System.out.print(dataconn);
        try{
        Connection connDB= dataconn.defDataConn();  //调用数据库连接函数
        Statement stat = connDB.createStatement();  //初始化statement对象连接数据库
        String SQL = "select * from users";
        ResultSet res = stat.executeQuery(SQL);  //查询指定数据
        //遍历数据集合
        while(res.next()){
            String name = res.getNString(2);
            System.out.println("查询内容为："+name);
        }
        }catch(SQLException e){
            e.printStackTrace();
            System.out.println("连接失败");
        }
        
    } 
    @Test
    public void runSet(){
        Dataconn dataconn = new Dataconn("com.mysql.jdbc.Driver", "jdbc:mysql://127.0.0.1:3306/test", "root", "root@2017");
        System.out.print(dataconn);
        try{
        Connection connDB= dataconn.setConnDB();  //调用数据库连接函数
        Statement stat = connDB.createStatement();  //初始化statement对象连接数据库
        String SQL = "select * from users";
        ResultSet res = stat.executeQuery(SQL);  //查询指定数据
        //遍历数据集合
        while(res.next()){
            String name = res.getNString(2);
            System.out.println("查询内容为："+name);
        }
        connDB.close();
        }catch(SQLException e){
            e.printStackTrace();
            System.out.println("连接失败");
        }
            
    }
    @Test
    public void openFileconn() throws IOException, ClassNotFoundException, SQLException{
        Dataconn dataconn = new Dataconn();
        System.out.print(dataconn);
        try{
        Connection connDB= dataconn.openFileconn();  //调用数据库连接函数
        Statement stat = connDB.createStatement();  //初始化statement对象连接数据库
        String SQL = "select * from users";
        ResultSet res = stat.executeQuery(SQL);  //查询指定数据
        //遍历数据集合
        while(res.next()){
            String name = res.getNString(2);
            System.out.println("查询内容为："+name);
        }
        }catch(IOException e){
            e.printStackTrace();
            System.out.println("打开文件失败");
        }
    }

}