properties + IO 读取配置文件

1.项目目录树

　　

2.配置文件config.properties
　　username = sushe
　　password = sushe
　　url = jdbc:mysql://172.16.100.10:3306/sushe?useUnicode=true&characterEncoding=GBK
　　jdbcDriverName = com.mysql.jdbc.Driver

3.JdbcBean对象,用来存储jdbc链接信息

package com.dlab.bean;
    
    public class JdbcBean {
    
        private String userName;
        
        private String password;
        
        private String Url;
        
        private String jdbcDriverName;
    
        public String getUserName() {
            return userName;
        }
    
        public void setUserName(String userName) {
            this.userName = userName;
        }
    
        public String getPassword() {
            return password;
        }
    
        public void setPassword(String password) {
            this.password = password;
        }
    
        public String getUrl() {
            return Url;
        }
    
        public void setUrl(String url) {
            Url = url;
        }
    
        public String getJdbcDriverName() {
            return jdbcDriverName;
        }
    
        public void setJdbcDriverName(String jdbcDriverName) {
            this.jdbcDriverName = jdbcDriverName;
        }
        
        
    }

4.读取配置文件工具JdbcConfig.java

package com.dlab.util;
    
    import java.io.IOException;
    import java.io.InputStream;
    import java.util.Properties;
    
    import com.dlab.bean.JdbcBean;
    
    public class JdbcConfig {
    
        private JdbcBean jdbcBean;
        
        public JdbcConfig()  throws IOException{
                
                //使用InputStream读取配置文件
                InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream("config.properties");
                Properties configReader = new Properties();
                //加载配置文件
                configReader.load(in);
                
                jdbcBean = new JdbcBean();
                
                jdbcBean.setUserName(configReader.getProperty("username"));
                jdbcBean.setPassword(configReader.getProperty("password"));
                jdbcBean.setUrl(configReader.getProperty("url"));
                jdbcBean.setJdbcDriverName(configReader.getProperty("jdbcDriverName"));
        
        }
        
        //返回JdbcBean对象
        public JdbcBean getConfigInfo(){
            return jdbcBean;
        }
        
    }

5.JDBC工具DBUtil.java,获取Connection

package com.dlab.util;
    
    import java.io.IOException;
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    
    import com.dlab.bean.JdbcBean;
    
    public class DBUtil {
    
        /**
         * 采用单例模式
         */
        private static DBUtil instance = new DBUtil();
        private Connection conn;
        
        private DBUtil (){
            JdbcBean jdbcBean;
            try {
                jdbcBean = new JdbcConfig().getConfigInfo();
                Class.forName(jdbcBean.getJdbcDriverName());
                conn = DriverManager.getConnection(jdbcBean.getUrl(), jdbcBean.getUserName(), jdbcBean.getPassword());
            } catch (IOException e) {
                e.printStackTrace();
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            
        }
        
        public static synchronized DBUtil getInstance (){
            return instance;
        }
        
        //返回Connection
        public Connection getConn(){
            return conn;
        }
        
        //Connection的静态关闭方法
        public static void close(Connection conn){
            if(conn != null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        
        //PreparedStatement的静态关闭方法
        public static void close(PreparedStatement pstmt){
            if(pstmt != null){
                try {
                    pstmt.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        
        //ResultSet的静态关闭方法
        public static void close(ResultSet rs){
            if(rs != null){
                try {
                    rs.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }

6.测试程序DBTest.java

package com.dlab.dbtest;
    
    import java.sql.Connection;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    
    import com.dlab.util.DBUtil;
    
    public class DBTest {
    
        public static void main(String[] args) {
            String sql = "select * from Admin";
            Connection conn = null;
            PreparedStatement pstmt = null;
            ResultSet rs = null;
            
            try {
                conn = DBUtil.getInstance().getConn();
                pstmt = conn.prepareStatement(sql);
                rs = pstmt.executeQuery();
                while(rs.next()){
                    System.out.println(rs.getString("Admin_Username"));
                }
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                DBUtil.close(rs);
                DBUtil.close(pstmt);
                DBUtil.close(conn);
            }
            
        }
    
    }