java JDBC (五) properties配置文件

1、在src目录下创建文件 database.properties

driver = com.mysql.jdbc.Driver
url = jdbc:mysql://192.168.0.207:3306/mydb
user = root
pwd = XXXXXXXXXXXX

2、创建读取配置文件信息的类DBProperties.java

package cn.sasa.demo4;

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

public class DBProperties {
    public static String driver = "";
    public static String url = "";
    public static String user = "";
    public static String pwd = "";

    static {
        // 类的加载器
        try {
            InputStream input = DBProperties.class.getClassLoader().getResourceAsStream("database.properties");
            Properties properties = new Properties();
            properties.load(input);
            driver = properties.getProperty("driver");
            url = properties.getProperty("url");
            user = properties.getProperty("user");
            pwd = properties.getProperty("pwd");
        }catch(IOException ex) {

        }

    }
}

3、JDBC的工具类

package cn.sasa.demo4;

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

/***
 * JDBC 工具类
 * @author THTF
 *
 */
public class JDBCUtil {

    private JDBCUtil() {}

    private static Connection conn;

    static {
        try {
            Class.forName(DBProperties.driver);
            String url = DBProperties.url;
            String user = DBProperties.user;
            String pwd = DBProperties.pwd;
            conn = DriverManager.getConnection(url, user, pwd);
        }catch(Exception ex){
            throw new RuntimeException(ex + "数据库连接失败");
        }
    }

    /**
     * 获得连接
     */
    public static Connection getConn() {
        return conn;
    }

    /**
     * 关闭资源
     */
    public static void close(Connection con, Statement state, ResultSet rs) {
        if(con != null) {
            try {
                con.close();
            }catch(SQLException ex){

            }
        }
        if(state != null) {
            try {
                state.close();
            }catch(SQLException ex){

            }
        }
        if(rs != null) {
            try {
                rs.close();
            }catch(SQLException ex){

            }
        }
    }

    public static void close(Connection con, Statement state) {
        if(con != null) {
            try {
                con.close();
            }catch(SQLException ex){

            }
        }
        if(state != null) {
            try {
                state.close();
            }catch(SQLException ex){

            }
        }
    }
}

4、测试类

package cn.sasa.demo4;

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

public class TestJDBCUtil {
    public static void main(String[] args) throws SQLException {
        Connection conn = JDBCUtil.getConn();

        String sql = "SELECT * FROM product;";
        PreparedStatement pstate = conn.prepareStatement(sql);
        ResultSet rs = pstate.executeQuery();

        ArrayList<Product> plist = new ArrayList<Product>();
        while(rs.next()) {
            Product p = new Product(rs.getInt("pid"),
                    rs.getString("pname"),
                    rs.getDouble("price"),
                    rs.getString("ptype"),
                    rs.getString("create_tm")
                    );
            plist.add(p);
        }

        JDBCUtil.close(conn, pstate, rs);

        for(var p : plist) {
            System.out.println(p.getPname() +"\t"+ p.getPrice());
        }
    }
}