Java jdbc 连接数据库、通用增删改查、事务回滚

1.先下载mysql-connector-java-5.1.40.jar包；

2.写代码；

获取数据库连接、通用查询和同意增删改代码：

    public static Connection getConnection() {
        Connection con = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            System.out.println("数据库驱动加载成功");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        try {
            con = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/maxinhai?characterEncoding=UTF-8",
                    "maxinhai", "maxinhai");
            System.out.println("数据库连接成功");
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return con;
    }

    /**
     * 执行增加、删除、修改 sql操作
     * 
     * @auther maxinhai
     * @param con 连接对象
     * @param sql 增加、删除、修改sql语句
     * @param params 条件参数
     * @return 查询结果
     */
    public static int executeUpdate(Connection con, String sql, List<Object> params) {
        int num = 0;
        PreparedStatement ps = null;
        try {
            // 预处理对象
            System.out.println(sql);
            ps = con.prepareStatement(sql);
            // 填充参数
            if (params.size() > 0) {
                for (int i = 0; i < params.size(); i++) {
                    ps.setObject(i + 1, params.get(i));
                }
            }
            // 执行sql
            num = ps.executeUpdate();
            System.out.println("影响了" + num + "条信息");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (ps != null)
                    ps.close();
                if (con != null)
                    con.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return num;
    }

    /**
     * 执行查询语句
     * 
     * @auther maxinhai
     * @param con 连接对象
     * @param querySql 查询语句
     * @param params 查询条件参数
     * @return 查询结果
     */
    public static List<Map<String, Object>> executeQuery(Connection con, String querySql, List<Object> params) {
        List<Map<String, Object>> table = null;
        PreparedStatement ps = null;
        ResultSet queryResult = null;
        try {
            // 获取预处理对象
            ps = con.prepareStatement(querySql);
            // 填充参数
            if (params != null && params.size() > 0) {
                for (int i = 0; i < params.size(); i++) {
                    ps.setObject(i + 1, params.get(i));
                }
            }
            // 执行查询
            queryResult = ps.executeQuery();
            // 获取键名
            ResultSetMetaData md = queryResult.getMetaData();
            // 获取行的数量
            int columnCount = md.getColumnCount();
            table = new ArrayList();
            while (queryResult.next()) {
                // 链表保证顺序
                Map<String, Object> rowData = new LinkedHashMap<>();
                for (int i = 1; i <= columnCount; i++) {
                    // 获取键名及值
                    rowData.put(md.getColumnName(i), queryResult.getObject(i));
                }
                table.add(rowData);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            try {
                if (ps != null)
                    ps.close();
                if (con != null)
                    con.close();
                if (queryResult != null)
                    queryResult.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return table;
    }

测试代码：

    public static void main(String[] args) throws InterruptedException {

        Connection connect = getConnection();
        String sql = "select * from user_info where name=?";
        List<Object> params = new ArrayList<>(1);
        params.add("tom");
        List<Map<String, Object>> result = executeQuery(connect, sql, params);

        if (result.size() == 1) {
            result.get(0).forEach((k, v) -> {
                System.out.print(k + "=>" + v + "\t");
            });
        } else {
            result.forEach(item -> {
                item.forEach((k, v) -> {
                    System.out.print(k + "=>" + v + "\t");
                });
                System.out.println();
            });
        }
        
        connect = getConnection();
        String insert = "insert into user_info(name,sex,age,address) values(?,?,?,?)";
        List<Object> paramList = new ArrayList<>(4);
        paramList.add("maxinhai");
        paramList.add(1);
        paramList.add(12);
        paramList.add(1);
        int count = executeUpdate(connect, insert, paramList);
        
    }

事务回滚代码：

    /**
     * jdbc事务
     * @throws SQLException 
     * @throws InterruptedException 
     */
    public static void transaction() throws SQLException, InterruptedException {
        Connection connect = getConnection();
        //关闭自动提交事务
        connect.setAutoCommit(false);
        int flag = 0;
        
        String insert1 = "insert into user_school(school_id,school_name,school_address,school_type) values(?,?,?,?)";
        List<Object> params = new ArrayList<>(4);
        params.add(5003);
        params.add("清华大学");
        params.add("中关村");
        params.add("本科");
        try {
            int i = 100/0; //报错
            executeUpdate(connect, insert1, params);
        } catch (Exception e) {
            System.out.println("执行" + insert1 + "语句出错，回滚事务");
            flag++;
        } 
        
        Thread.sleep(3000);
        
        String insert2 = "insert into user_info(name,sex,age,address,school1) values(?,?,?,?,?)";
        List<Object> paramList = new ArrayList<>(5);
        paramList.add("666先生的救赎");
        paramList.add(1);
        paramList.add(12);
        paramList.add(1);
        paramList.add(5002);
        try {
            executeUpdate(connect, insert2, paramList);
        } catch (Exception e) {
            System.out.println("执行" + insert2 + "语句出错，回滚事务");
            flag++;
        }
        
        if(flag > 0) {
            System.out.println("事务管理: 两个事务都会滚");
            connect.rollback();
        }
        connect.commit();
        connect.close();
    }

上面事务代码是调用通用增删改代码实现的，需要把通用代码里的关闭数据库连接代码注释掉，事务需要在同一个数据库连接里实现；