JDBCUtil

Posted 2020-09-22

一、jdbcUtil类

    package com.test.util;  
      
    import java.io.InputStream;  
    import java.sql.Connection;  
    import java.sql.DriverManager;  
    import java.sql.PreparedStatement;  
    import java.sql.ResultSet;  
    import java.sql.ResultSetMetaData;  
    import java.sql.SQLException;  
    import java.util.ArrayList;  
    import java.util.HashMap;  
    import java.util.List;  
    import java.util.Map;  
    import java.util.Properties;  
      
    public class JdbcUtil {  
      
        // 表示定义数据库的用户名  
        private static String USERNAME ;  
      
        // 定义数据库的密码  
        private static String PASSWORD;  
      
        // 定义数据库的驱动信息  
        private static String DRIVER;  
      
        // 定义访问数据库的地址  
        private static String URL;  
      
        // 定义数据库的链接  
        private Connection connection;  
      
        // 定义sql语句的执行对象  
        private PreparedStatement pstmt;  
      
        // 定义查询返回的结果集合  
        private ResultSet resultSet;  
          
        static{  
            //加载数据库配置信息，并给相关的属性赋值  
            loadConfig();  
        }  
      
        /** 
         * 加载数据库配置信息，并给相关的属性赋值 
         */  
        public static void loadConfig() {  
            try {  
                InputStream inStream = JdbcUtil.class  
                        .getResourceAsStream("/jdbc.properties");  
                Properties prop = new Properties();  
                prop.load(inStream);  
                USERNAME = prop.getProperty("jdbc.username");  
                PASSWORD = prop.getProperty("jdbc.password");  
                DRIVER= prop.getProperty("jdbc.driver");  
                URL = prop.getProperty("jdbc.url");  
            } catch (Exception e) {  
                throw new RuntimeException("读取数据库配置文件异常！", e);  
            }  
        }  
      
        public JdbcUtil() {  
      
        }  
      
        /** 
         * 获取数据库连接 
         *  
         * @return 数据库连接 
         */  
        public Connection getConnection() {  
            try {  
                Class.forName(DRIVER); // 注册驱动  
                connection = DriverManager.getConnection(URL, USERNAME, PASSWORD); // 获取连接  
            } catch (Exception e) {  
                throw new RuntimeException("get connection error!", e);  
            }  
            return connection;  
        }  
      
        /** 
         * 执行更新操作 
         *  
         * @param sql 
         *            sql语句 
         * @param params 
         *            执行参数 
         * @return 执行结果 
         * @throws SQLException 
         */  
        public boolean updateByPreparedStatement(String sql, List<?> params)  
                throws SQLException {  
            boolean flag = false;  
            int result = -1;// 表示当用户执行添加删除和修改的时候所影响数据库的行数  
            pstmt = connection.prepareStatement(sql);  
            int index = 1;  
            // 填充sql语句中的占位符  
            if (params != null && !params.isEmpty()) {  
                for (int i = 0; i < params.size(); i++) {  
                    pstmt.setObject(index++, params.get(i));  
                }  
            }  
            result = pstmt.executeUpdate();  
            flag = result > 0 ? true : false;  
            return flag;  
        }  
      
        /** 
         * 执行查询操作 
         *  
         * @param sql 
         *            sql语句 
         * @param params 
         *            执行参数 
         * @return 
         * @throws SQLException 
         */  
        public List<Map<String, Object>> findResult(String sql, List<?> params)  
                throws SQLException {  
            List<Map<String, Object>> list = new ArrayList<Map<String, Object>>();  
            int index = 1;  
            pstmt = connection.prepareStatement(sql);  
            if (params != null && !params.isEmpty()) {  
                for (int i = 0; i < params.size(); i++) {  
                    pstmt.setObject(index++, params.get(i));  
                }  
            }  
            resultSet = pstmt.executeQuery();  
            ResultSetMetaData metaData = resultSet.getMetaData();  
            int cols_len = metaData.getColumnCount();  
            while (resultSet.next()) {  
                Map<String, Object> map = new HashMap<String, Object>();  
                for (int i = 0; i < cols_len; i++) {  
                    String cols_name = metaData.getColumnName(i + 1);  
                    Object cols_value = resultSet.getObject(cols_name);  
                    if (cols_value == null) {  
                        cols_value = "";  
                    }  
                    map.put(cols_name, cols_value);  
                }  
                list.add(map);  
            }  
            return list;  
        }  
      
        /** 
         * 释放资源 
         */  
        public void releaseConn() {  
            if (resultSet != null) {  
                try {  
                    resultSet.close();  
                } catch (SQLException e) {  
                    e.printStackTrace();  
                }  
            }  
            if (pstmt != null) {  
                try {  
                    pstmt.close();  
                } catch (SQLException e) {  
                    e.printStackTrace();  
                }  
            }  
            if (connection != null) {  
                try {  
                    connection.close();  
                } catch (SQLException e) {  
                    e.printStackTrace();  
                }  
            }  
        }  
      
        public static void main(String[] args) {  
            JdbcUtil jdbcUtil = new JdbcUtil();  
            jdbcUtil.getConnection();  
            try {  
                List<Map<String, Object>> result = jdbcUtil.findResult(  
                        "select * from t_student", null);  
                for (Map<String, Object> m : result) {  
                    System.out.println(m);  
                }  
            } catch (SQLException e) {  
                e.printStackTrace();  
            } finally {  
                jdbcUtil.releaseConn();  
            }  
        }  
    }  

二、配置数据库资源

在根目录下新建jdbc.properties文件，用于管理数据库地址和用户名密码。内容如下：

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

三、应用类

    package com.test;  
      
    import java.sql.SQLException;  
    import java.util.ArrayList;  
    import java.util.List;  
    import java.util.Map;  
      
    import org.junit.Test;  
      
    import com.test.util.JdbcUtil;  
      
    public class JdbcTest {  
      
              
        /** 
         * 更新用户信息 
         */  
        @Test  
        public void updateUser(){  
            String name = "张三";  
            int age = 18;  
            int score = 60;  
            int id =1;  
            String sql = "update test_table set name=?,age=?,score=? where id=?";  
            //创建填充参数的list  
            List<Object> paramList = new ArrayList<Object>();  
            //填充参数  
            paramList.add(name);  
            paramList.add(age);  
            paramList.add(score);  
            paramList.add(id);  
              
            JdbcUtil jdbcUtil = null;  
            boolean bool = false;  
            try {  
                jdbcUtil = new JdbcUtil();  
                jdbcUtil.getConnection(); // 获取数据库链接  
                bool = jdbcUtil.updateByPreparedStatement(sql, paramList);  
            } catch (SQLException e) {  
                System.out.println(this.getClass()+"执行更新操作抛出异常！");  
                e.printStackTrace();  
            } finally {  
                if (jdbcUtil != null) {  
                    jdbcUtil.releaseConn(); // 一定要释放资源  
                }  
            }  
            System.out.println("执行更新的结果："+bool);  
        }  
          
          
        /** 
         * 根据id查询用户信息 
         */  
        @Test  
        public void findUserById(){  
            int id = 1;  
            String sql = "select * from test_table where id = ?";  
            //创建填充参数的list  
            List<Object> paramList = new ArrayList<Object>();  
            //填充参数  
            paramList.add(id);  
            JdbcUtil jdbcUtil = null;  
            try {  
                jdbcUtil = new JdbcUtil();  
                jdbcUtil.getConnection(); // 获取数据库链接  
                List<Map<String, Object>> mapList = jdbcUtil.findResult(  
                        sql.toString(), paramList);  
                if(mapList.size()==1){  
                    Map<String, Object> map = mapList.get(0);  
                    String name = (String) map.get("name");  
                    int age = (int) map.get("age");  
                    int score = (int) map.get("score");  
                    System.out.println("姓名:"+name+";年龄:"+age+";成绩:"+score);  
                }  
            } catch (SQLException e) {  
                System.out.println(this.getClass()+"执行查询操作抛出异常！");  
                e.printStackTrace();  
            } finally {  
                if (jdbcUtil != null) {  
                    jdbcUtil.releaseConn(); // 一定要释放资源  
                }  
            }  
      
        }  
    }  

四、执行结果 update==>执行更新的结果：true
find==>姓名:张三;年龄:18;成绩:60