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本文出自【DylanAndroid的博客】

玩转JDBC打造数据库操作万能工具类JDBCUtil，加入了高效的数据库连接池，利用了参数绑定有效防止SQL注入

在之前学习了MySQL和Oracle之后，那么，如和在Java种去连接这两种数据库。在这个轻量级的工具类当中，使用了数据库连接池
去提高数据库连接的高效性，并且使用了PreparedStatement来执行对SQL的预编译，能够有效防止SQL注入问题。

一.准备在配置文件配置:配置数据库连接属性文件：在项目新建config包下建立jdbc-mysql.properties并加入以下配置

jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/test?characterEncoding=utf8
jdbc.username=root
jdbc.password=root

二.准备数据库连接池对象：单例

package util;

import com.mchange.v2.c3p0.ComboPooledDataSource;
import com.mchange.v2.c3p0.DataSources;

import java.beans.PropertyVetoException;
import java.io.FileInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

/**
 * 数据库连接对象
 * Created by yuandl on 2016-12-16.
 */
public class DBConnectionPool {
    private static volatile DBConnectionPool dbConnection;
    private ComboPooledDataSource cpds;

    /**
     * 在构造函数初始化的时候获取数据库连接
     */
    private DBConnectionPool() {
        try {
            /**通过属性文件获取数据库连接的参数值**/
            Properties properties = new Properties();
            FileInputStream fileInputStream = new FileInputStream("src/config/jdbc-mysql.properties");
            properties.load(fileInputStream);
            /**获取属性文件中的值**/
            String driverClassName = properties.getProperty("jdbc.driverClassName");
            String url = properties.getProperty("jdbc.url");
            String username = properties.getProperty("jdbc.username");
            String password = properties.getProperty("jdbc.password");

            /**数据库连接池对象**/
            cpds = new ComboPooledDataSource();

            /**设置数据库连接驱动**/
            cpds.setDriverClass(driverClassName);
            /**设置数据库连接地址**/
            cpds.setJdbcUrl(url);
            /**设置数据库连接用户名**/
            cpds.setUser(username);
            /**设置数据库连接密码**/
            cpds.setPassword(password);

            /**初始化时创建的连接数,应在minPoolSize与maxPoolSize之间取值.默认为3**/
            cpds.setInitialPoolSize(3);
            /**连接池中保留的最大连接数据.默认为15**/
            cpds.setMaxPoolSize(10);
            /**当连接池中的连接用完时，C3PO一次性创建新的连接数目;**/
            cpds.setAcquireIncrement(1);
            /**隔多少秒检查所有连接池中的空闲连接,默认为0表示不检查;**/
            cpds.setIdleConnectionTestPeriod(60);
            /**最大空闲时间,超过空闲时间的连接将被丢弃.为0或负数据则永不丢弃.默认为0;**/
            cpds.setMaxIdleTime(3000);

            /**因性能消耗大请只在需要的时候使用它。如果设为true那么在每个connection提交的
             时候都将校验其有效性。建议使用idleConnectionTestPeriod或automaticTestTable
             等方法来提升连接测试的性能。Default: false**/
            cpds.setTestConnectionOnCheckout(true);

            /**如果设为true那么在取得连接的同时将校验连接的有效性。Default: false **/
            cpds.setTestConnectionOnCheckin(true);
            /**定义在从数据库获取新的连接失败后重复尝试获取的次数，默认为30;**/
            cpds.setAcquireRetryAttempts(30);
            /**两次连接中间隔时间默认为1000毫秒**/
            cpds.setAcquireRetryDelay(1000);
            /** 获取连接失败将会引起所有等待获取连接的线程异常,
             但是数据源仍有效的保留,并在下次调用getConnection()的时候继续尝试获取连接.如果设为true,
             那么尝试获取连接失败后该数据源将申明已经断开并永久关闭.默认为false**/
            cpds.setBreakAfterAcquireFailure(true);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (PropertyVetoException e) {
            e.printStackTrace();
        }

    }

    /**
     * 获取数据库连接对象，单例
     *
     * @return
     */
    public static DBConnectionPool getInstance() {
        if (dbConnection == null) {
            synchronized (DBConnectionPool.class) {
                if (dbConnection == null) {
                    dbConnection = new DBConnectionPool();
                }
            }
        }
        return dbConnection;
    }

    /**
     * 获取数据库连接
     *
     * @return 数据库连接
     */
    public final synchronized Connection getConnection() throws SQLException {
        return cpds.getConnection();
    }

    /**
     * finalize()方法是在垃圾收集器删除对象之前对这个对象调用的。
     *
     * @throws Throwable
     */
    protected void finalize() throws Throwable {
        DataSources.destroy(cpds);
        super.finalize();
    }
}

三.实现新增、修改、删除、查询操作的两个核心方法：可以实现任何复杂的SQL,而且通过数据绑定的方式不会有SQL注入问题

    /**
     * 可以执行新增，修改，删除
     *
     * @param sql      sql语句
     * @param bindArgs 绑定参数
     * @return 影响的行数
     * @throws SQLException SQL异常
     */
    public static int executeUpdate(String sql, Object[] bindArgs) throws SQLException {
        /**影响的行数**/
        int affectRowCount = -1;
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        try {
            /**从数据库连接池中获取数据库连接**/
            connection = DBConnectionPool.getInstance().getConnection();
            /**执行SQL预编译**/
            preparedStatement = connection.prepareStatement(sql.toString());
            /**设置不自动提交，以便于在出现异常的时候数据库回滚**/
            connection.setAutoCommit(false);
            System.out.println(getExecSQL(sql, bindArgs));
            if (bindArgs != null) {
                /**绑定参数设置sql占位符中的值**/
                for (int i = 0; i < bindArgs.length; i++) {
                    preparedStatement.setObject(i + 1, bindArgs[i]);
                }
            }
            /**执行sql**/
            affectRowCount = preparedStatement.executeUpdate();
            connection.commit();
            String operate;
            if (sql.toUpperCase().indexOf("DELETE FROM") != -1) {
                operate = "删除";
            } else if (sql.toUpperCase().indexOf("INSERT INTO") != -1) {
                operate = "新增";
            } else {
                operate = "修改";
            }
            System.out.println("成功" + operate + "了" + affectRowCount + "行");
            System.out.println();
        } catch (Exception e) {
            if (connection != null) {
                connection.rollback();
            }
            e.printStackTrace();
            throw e;
        } finally {
            if (preparedStatement != null) {
                preparedStatement.close();
            }
            if (connection != null) {
                connection.close();
            }
        }
        return affectRowCount;
    }


   /**
     * 执行查询
     *
     * @param sql      要执行的sql语句
     * @param bindArgs 绑定的参数
     * @return List<Map<String, Object>>结果集对象
     * @throws SQLException SQL执行异常
     */
    public static List<Map<String, Object>> executeQuery(String sql, Object[] bindArgs) throws SQLException {
        List<Map<String, Object>> datas = new ArrayList<>();
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            /**获取数据库连接池中的连接**/
            connection = DBConnectionPool.getInstance().getConnection();
            preparedStatement = connection.prepareStatement(sql);
            if (bindArgs != null) {
                /**设置sql占位符中的值**/
                for (int i = 0; i < bindArgs.length; i++) {
                    preparedStatement.setObject(i + 1, bindArgs[i]);
                }
            }
            System.out.println(getExecSQL(sql, bindArgs));
            /**执行sql语句，获取结果集**/
            resultSet = preparedStatement.executeQuery();
            getDatas(resultSet);
            System.out.println();
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        } finally {
            if (resultSet != null) {
                resultSet.close();
            }
            if (preparedStatement != null) {
                preparedStatement.close();
            }
            if (connection != null) {
                connection.close();
            }
        }
        return datas;
    }

四.执行新增的简化操作

 /**
     * 执行数据库插入操作
     *
     * @param valueMap  插入数据表中key为列名和value为列对应的值的Map对象
     * @param tableName 要插入的数据库的表名
     * @return 影响的行数
     * @throws SQLException SQL异常
     */
    public static int insert(String tableName, Map<String, Object> valueMap) throws SQLException {

        /**获取数据库插入的Map的键值对的值**/
        Set<String> keySet = valueMap.keySet();
        Iterator<String> iterator = keySet.iterator();
        /**要插入的字段sql，其实就是用key拼起来的**/
        StringBuilder columnSql = new StringBuilder();
        /**要插入的字段值，其实就是？**/
        StringBuilder unknownMarkSql = new StringBuilder();
        Object[] bindArgs = new Object[valueMap.size()];
        int i = 0;
        while (iterator.hasNext()) {
            String key = iterator.next();
            columnSql.append(i == 0 ? "" : ",");
            columnSql.append(key);

            unknownMarkSql.append(i == 0 ? "" : ",");
            unknownMarkSql.append("?");
            bindArgs[i] = valueMap.get(key);
            i++;
        }
        /**开始拼插入的sql语句**/
        StringBuilder sql = new StringBuilder();
        sql.append("INSERT INTO ");
        sql.append(tableName);
        sql.append(" (");
        sql.append(columnSql);
        sql.append(" )  VALUES (");
        sql.append(unknownMarkSql);
        sql.append(" )");
        return executeUpdate(sql.toString(), bindArgs);
    }

五.执行更新的简化操作

  /**
     * 执行更新操作
     *
     * @param tableName 表名
     * @param valueMap  要更改的值
     * @param whereMap  条件
     * @return 影响的行数
     * @throws SQLException SQL异常
     */
    public static int update(String tableName, Map<String, Object> valueMap, Map<String, Object> whereMap) throws SQLException {
        /**获取数据库插入的Map的键值对的值**/
        Set<String> keySet = valueMap.keySet();
        Iterator<String> iterator = keySet.iterator();
        /**开始拼插入的sql语句**/
        StringBuilder sql = new StringBuilder();
        sql.append("UPDATE ");
        sql.append(tableName);
        sql.append(" SET ");

        /**要更改的的字段sql，其实就是用key拼起来的**/
        StringBuilder columnSql = new StringBuilder();
        int i = 0;
        List<Object> objects = new ArrayList<>();
        while (iterator.hasNext()) {
            String key = iterator.next();
            columnSql.append(i == 0 ? "" : ",");
            columnSql.append(key + " = ? ");
            objects.add(valueMap.get(key));
            i++;
        }
        sql.append(columnSql);

        /**更新的条件:要更改的的字段sql，其实就是用key拼起来的**/
        StringBuilder whereSql = new StringBuilder();
        int j = 0;
        if (whereMap != null && whereMap.size() > 0) {
            whereSql.append(" WHERE ");
            iterator = whereMap.keySet().iterator();
            while (iterator.hasNext()) {
                String key = iterator.next();
                whereSql.append(j == 0 ? "" : " AND ");
                whereSql.append(key + " = ? ");
                objects.add(whereMap.get(key));
                j++;
            }
            sql.append(whereSql);
        }
        return executeUpdate(sql.toString(), objects.toArray());
    }

六.执行删除的简化操作

  /**
     * 执行删除操作
     *
     * @param tableName 要删除的表名
     * @param whereMap  删除的条件
     * @return 影响的行数
     * @throws SQLException SQL执行异常
     */
    public static int delete(String tableName, Map<String, Object> whereMap) throws SQLException {
        /**准备删除的sql语句**/
        StringBuilder sql = new StringBuilder();
        sql.append("DELETE FROM ");
        sql.append(tableName);

        /**更新的条件:要更改的的字段sql，其实就是用key拼起来的**/
        StringBuilder whereSql = new StringBuilder();
        Object[] bindArgs = null;
        if (whereMap != null && whereMap.size() > 0) {
            bindArgs = new Object[whereMap.size()];
            whereSql.append(" WHERE ");
            /**获取数据库插入的Map的键值对的值**/
            Set<String> keySet = whereMap.keySet();
            Iterator<String> iterator = keySet.iterator();
            int i = 0;
            while (iterator.hasNext()) {
                String key = iterator.next();
                whereSql.append(i == 0 ? "" : " AND ");
                whereSql.append(key + " = ? ");
                bindArgs[i] = whereMap.get(key);
                i++;
            }
            sql.append(whereSql);
        }
        return executeUpdate(sql.toString(), bindArgs);
    }

七.查询的4种玩法

1.执行sql通过 Map限定查询条件查询

/**
   * 1..执行sql通过 Map<String, Object>限定查询条件查询
   *
   * @param tableName 表名
   * @param whereMap  where条件
   * @return List<Map<String, Object>>
   * @throws SQLException
   */
  public static List<Map<String, Object>> query(String tableName,
                                                Map<String, Object> whereMap) throws SQLException {
      String whereClause = "";
      Object[] whereArgs = null;
      if (whereMap != null && whereMap.size() > 0) {
          Iterator<String> iterator = whereMap.keySet().iterator();
          whereArgs = new Object[whereMap.size()];
          int i = 0;
          while (iterator.hasNext()) {
              String key = iterator.next();
              whereClause += (i == 0 ? "" : " AND ");
              whereClause += (key + " = ? ");
              whereArgs[i] = whereMap.get(key);
              i++;
          }
      }
      return query(tableName, false, null, whereClause, whereArgs, null, null, null, null);
  }

2.执行sql条件参数绑定形式的查询

  /**
   * 2.执行sql条件参数绑定形式的查询
   *
   * @param tableName   表名
   * @param whereClause where条件的sql
   * @param whereArgs   where条件中占位符中的值
   * @return List<Map<String, Object>>
   * @throws SQLException
   */
  public static List<Map<String, Object>> query(String tableName,
                                                String whereClause,
                                                String[] whereArgs) throws SQLException {
      return query(tableName, false, null, whereClause, whereArgs, null, null, null, null);
  }

3.包含所有的查询条件的查询方法

   /**
    * 执行全部结构的sql查询
    *
    * @param tableName     表名
    * @param distinct      去重
    * @param columns       要查询的列名
    * @param selection     where条件
    * @param selectionArgs where条件中占位符中的值
    * @param groupBy       分组
    * @param having        筛选
    * @param orderBy       排序
    * @param limit         分页
    * @return List<Map<String, Object>>
    * @throws SQLException
    */
   public static List<Map<String, Object>> query(String tableName,
                                                 boolean distinct,
                                                 String[] columns,
                                                 String selection,
                                                 Object[] selectionArgs,
                                                 String groupBy,
                                                 String having,
                                                 String orderBy,
                                                 String limit) throws SQLException {
       String sql = buildQueryString(distinct, tableName, columns, selection, groupBy, having, orderBy, limit);
       return executeQuery(sql, selectionArgs);
     }

4.通过单纯的sql查询数据,慎用，会有sql注入问题，只是为了方便查询，实际开发中不会去使用这个方法

     * 4.通过sql查询数据,
     * 慎用，会有sql注入问题只是为了方便查询，实际开发中不会去使用这个方法
     *
     * @param sql
     * @return 查询的数据集合
     * @throws SQLException
     */
    public static List<Map<String, Object>> query(String sql) throws SQLException {
        return executeQuery(sql, null);
    }

八.DBUtil的完整代码

package util;

import com.sun.istack.internal.Nullable;

import java.sql.*;
import java.util.*;
import java.util.regex.Pattern;

/**
* 数据库JDBC连接工具类
* Created by yuandl on 2016-12-16.
*/
public class DBUtil {

 /**
  * 执行数据库插入操作
  *
  * @param valueMap  插入数据表中key为列名和value为列对应的值的Map对象
  * @param tableName 要插入的数据库的表名
  * @return 影响的行数
  * @throws SQLException SQL异常
  */
 public static int insert(String tableName, Map<String, Object> valueMap) throws SQLException {

     /**获取数据库插入的Map的键值对的值**/
     Set<String> keySet = valueMap.keySet();
     Iterator<String> iterator = keySet.iterator();
     /**要插入的字段sql，其实就是用key拼起来的**/
     StringBuilder columnSql = new StringBuilder();
     /**要插入的字段值，其实就是？**/
     StringBuilder unknownMarkSql = new StringBuilder();
     Object[] bindArgs = new Object[valueMap.size()];
     int i = 0;
     while (iterator.hasNext()) {
         String key = iterator.next();
         columnSql.append(i == 0 ? "" : ",");
         columnSql.append(key);

         unknownMarkSql.append(i == 0 ? "" : ",");
         unknownMarkSql.append("?");
         bindArgs[i] = valueMap.get(key);
         i++;
     }
     /**开始拼插入的sql语句**/
     StringBuilder sql = new StringBuilder();
     sql.append("INSERT INTO ");
     sql.append(tableName);
     sql.append(" (");
     sql.append(columnSql);
     sql.append(" )  VALUES (");
     sql.append(unknownMarkSql);
     sql.append(" )");
     return executeUpdate(sql.toString(), bindArgs);
 }

 /**
  * 执行更新操作
  *
  * @param tableName 表名
  * @param valueMap  要更改的值
  * @param whereMap  条件
  * @return 影响的行数
  * @throws SQLException SQL异常
  */
 public static int update(String tableName, Map<String, Object> valueMap, Map<String, Object> whereMap) throws SQLException {
     /**获取数据库插入的Map的键值对的值**/
     Set<String> keySet = valueMap.keySet();
     Iterator<String> iterator = keySet.iterator();
     /**开始拼插入的sql语句**/
     StringBuilder sql = new StringBuilder();
     sql.append("UPDATE ");
     sql.append(tableName);
     sql.append(" SET ");

     /**要更改的的字段sql，其实就是用key拼起来的**/
     StringBuilder columnSql = new StringBuilder();
     int i = 0;
     List<Object> objects = new ArrayList<>();
     while (iterator.hasNext()) {
         String key = iterator.next();
         columnSql.append(i == 0 ? "" : ",");
         columnSql.append(key + " = ? ");
         objects.add(valueMap.get(key));
         i++;
     }
     sql.append(columnSql);

     /**更新的条件:要更改的的字段sql，其实就是用key拼起来的**/
     StringBuilder whereSql = new StringBuilder();
     int j = 0;
     if (whereMap != null && whereMap.size() > 0) {
         whereSql.append(" WHERE ");
         iterator = whereMap.keySet().iterator();
         while (iterator.hasNext()) {
             String key = iterator.next();
             whereSql.append(j == 0 ? "" : " AND ");
             whereSql.append(key + " = ? ");
             objects.add(whereMap.get(key));
             j++;
         }
         sql.append(whereSql);
     }
     return executeUpdate(sql.toString(), objects.toArray());
 }

 /**
  * 执行删除操作
  *
  * @param tableName 要删除的表名
  * @param whereMap  删除的条件
  * @return 影响的行数
  * @throws SQLException SQL执行异常
  */
 public static int delete(String tableName, Map<String, Object> whereMap) throws SQLException {
     /**准备删除的sql语句**/
     StringBuilder sql = new StringBuilder();
     sql.append("DELETE FROM ");
     sql.append(tableName);

     /**更新的条件:要更改的的字段sql，其实就是用key拼起来的**/
     StringBuilder whereSql = new StringBuilder();
     Object[] bindArgs = null;
     if (whereMap != null && whereMap.size() > 0) {
         bindArgs = new Object[whereMap.size()];
         whereSql.append(" WHERE ");
         /**获取数据库插入的Map的键值对的值**/
         Set<String> keySet = whereMap.keySet();
         Iterator<String> iterator = keySet.iterator();
         int i = 0;
         while (iterator.hasNext()) {
             String key = iterator.next();
             whereSql.append(i == 0 ? "" : " AND ");
             whereSql.append(key + " = ? ");
             bindArgs[i] = whereMap.get(key);
             i++;
         }
         sql.append(whereSql);
     }
     return executeUpdate(sql.toString(), bindArgs);
 }

 /**
  * 可以执行新增，修改，删除
  *
  * @param sql      sql语句
  * @param bindArgs 绑定参数
  * @return 影响的行数
  * @throws SQLException SQL异常
  */
 public static int executeUpdate(String sql, Object[] bindArgs) throws SQLException {
     /**影响的行数**/
     int affectRowCount = -1;
     Connection connection = null;
     PreparedStatement preparedStatement = null;
     try {
         /**从数据库连接池中获取数据库连接**/
         connection = DBConnectionPool.getInstance().getConnection();
         /**执行SQL预编译**/
         preparedStatement = connection.prepareStatement(sql.toString());
         /**设置不自动提交，以便于在出现异常的时候数据库回滚**/
         connection.setAutoCommit(false);
         System.out.println(getExecSQL(sql, bindArgs));
         if (bindArgs != null) {
             /**绑定参数设置sql占位符中的值**/
             for (int i = 0; i < bindArgs.length; i++) {
                 preparedStatement.setObject(i + 1, bindArgs[i]);
             }
         }
         /**执行sql**/
         affectRowCount = preparedStatement.executeUpdate();
         connection.commit();
         String operate;
         if (sql.toUpperCase().indexOf("DELETE FROM") != -1) {
             operate = "删除";
         } else if (sql.toUpperCase().indexOf("INSERT INTO") != -1) {
             operate = "新增";
         } else {
             operate = "修改";
         }
         System.out.println("成功" + operate + "了" + affectRowCount + "行");
         System.out.println();
     } catch (Exception e) {
         if (connection != null) {
             connection.rollback();
         }
         e.printStackTrace();
         throw e;
     } finally {
         if (preparedStatement != null) {
             preparedStatement.close();
         }
         if (connection != null) {
             connection.close();
         }
     }
     return affectRowCount;
 }

 /**
  * 通过sql查询数据,
  * 慎用，会有sql注入问题
  *
  * @param sql
  * @return 查询的数据集合
  * @throws SQLException
  */
 public static List<Map<String, Object>> query(String sql) throws SQLException {
     return executeQuery(sql, null);
 }

 /**
  * 执行sql通过 Map<String, Object>限定查询条件查询
  *
  * @param tableName 表名
  * @param whereMap  where条件
  * @return List<Map<String, Object>>
  * @throws SQLException
  */
 public static List<Map<String, Object>> query(String tableName,
                                               Map<String, Object> whereMap) throws SQLException {
     String whereClause = "";
     Object[] whereArgs = null;
     if (whereMap != null & whereMap.size() > 0) {
         Iterator<String> iterator = whereMap.keySet().iterator();
         whereArgs = new Object[whereMap.size()];
         int i = 0;
         while (iterator.hasNext()) {
             String key = iterator.next();
             whereClause += (i == 0 ? "" : " AND ");
             whereClause += (key + " = ? ");
             whereArgs[i] = whereMap.get(key);
             i++;
         }
     }
     return query(tableName, false, null, whereClause, whereArgs, null, null, null, null);
 }

 /**
  * 执行sql条件参数绑定形式的查询
  *
  * @param tableName   表名
  * @param whereClause where条件的sql
  * @param whereArgs   where条件中占位符中的值
  * @return List<Map<String, Object>>
  * @throws SQLException
  */
 public static List<Map<String, Object>> query(String tableName,
                                               String whereClause,
                                               String[] whereArgs) throws SQLException {
     return query(tableName, false, null, whereClause, whereArgs, null, null, null, null);
 }

 /**
  * 执行全部结构的sql查询
  *
  * @param tableName     表名
  * @param distinct      去重
  * @param columns       要查询的列名
  * @param selection     where条件
  * @param selectionArgs where条件中占位符中的值
  * @param groupBy       分组
  * @param having        筛选
  * @param orderBy       排序
  * @param limit         分页
  * @return List<Map<String, Object>>
  * @throws SQLException
  */
 public static List<Map<String, Object>> query(String tableName,
                                               boolean distinct,
                                               String[] columns,
                                               String selection,
                                               Object[] selectionArgs,
                                               String groupBy,
                                               String having,
                                               String orderBy,
                                               String limit) throws SQLException {
     String sql = buildQueryString(distinct, tableName, columns, selection, groupBy, having, orderBy, limit);
     return executeQuery(sql, selectionArgs);

 }

 /**
  * 执行查询
  *
  * @param sql      要执行的sql语句
  * @param bindArgs 绑定的参数
  * @return List<Map<String, Object>>结果集对象
  * @throws SQLException SQL执行异常
  */
 public static List<Map<String, Object>> executeQuery(String sql, Object[] bindArgs) throws SQLException {
     List<Map<String, Object>> datas = new ArrayList<>();
     Connection connection = null;
     PreparedStatement preparedStatement = null;
     ResultSet resultSet = null;

     try {
         /**获取数据库连接池中的连接**/
         connection = DBConnectionPool.getInstance().getConnection();
         preparedStatement = connection.prepareStatement(sql);
         if (bindArgs != null) {
             /**设置sql占位符中的值**/
             for (int i = 0; i < bindArgs.length; i++) {
                 preparedStatement.setObject(i + 1, bindArgs[i]);
             }
         }
         System.out.println(getExecSQL(sql, bindArgs));
         /**执行sql语句，获取结果集**/
         resultSet = preparedStatement.executeQuery();
         getDatas(resultSet);
         System.out.println();
     } catch (Exception e) {
         e.printStackTrace();
         throw e;
     } finally {
         if (resultSet != null) {
             resultSet.close();
         }
         if (preparedStatement != null) {
             preparedStatement.close();
         }
         if (connection != null) {
             connection.close();
         }
     }
     return datas;
 }


 /**
  * 将结果集对象封装成List<Map<String, Object>> 对象
  *
  * @param resultSet 结果多想
  * @return 结果的封装
  * @throws SQLException
  */
 private static List<Map<String, Object>> getDatas(ResultSet resultSet) throws SQLException {
     List<Map<String, Object>> datas = new ArrayList<>();
     /**获取结果集的数据结构对象**/
     ResultSetMetaData metaData = resultSet.getMetaData();
     while (resultSet.next()) {
         Map<String, Object> rowMap = new HashMap<>();
         for (int i = 1; i <= metaData.getColumnCount(); i++) {
             rowMap.put(metaData.getColumnName(i), resultSet.getObject(i));
         }
         datas.add(rowMap);
     }
     System.out.println("成功查询到了" + datas.size() + "行数据");
     for (int i = 0; i < datas.size(); i++) {
         Map<String, Object> map = datas.get(i);
         System.out.println("第" + (i + 1) + "行：" + map);
     }
     return datas;
 }


 /**
  * Build an SQL query string from the given clauses.
  *
  * @param distinct true if you want each row to be unique, false otherwise.
  * @param tables   The table names to compile the query against.
  * @param columns  A list of which columns to return. Passing null will
  *                 return all columns, which is discouraged to prevent reading
  *                 data from storage that isn't going to be used.
  * @param where    A filter declaring which rows to return, formatted as an SQL
  *                 WHERE clause (excluding the WHERE itself). Passing null will
  *                 return all rows for the given URL.
  * @param groupBy  A filter declaring how to group rows, formatted as an SQL
  *                 GROUP BY clause (excluding the GROUP BY itself). Passing null
  *                 will cause the rows to not be grouped.
  * @param having   A filter declare which row groups to include in the cursor,
  *                 if row grouping is being used, formatted as an SQL HAVING
  *                 clause (excluding the HAVING itself). Passing null will cause
  *                 all row groups to be included, and is required when row
  *                 grouping is not being used.
  * @param orderBy  How to order the rows, formatted as an SQL ORDER BY clause
  *                 (excluding the ORDER BY itself). Passing null will use the
  *                 default sort order, which may be unordered.
  * @param limit    Limits the number of rows returned by the query,
  *                 formatted as LIMIT clause. Passing null denotes no LIMIT clause.
  * @return the SQL query string
  */
 private static String buildQueryString(
         boolean distinct, String tables, String[] columns, String where,
         String groupBy, String having, String orderBy, String limit) {
     if (isEmpty(groupBy) && !isEmpty(having)) {
         throw new IllegalArgumentException(
                 "HAVING clauses are only permitted when using a groupBy clause");
     }
     if (!isEmpty(limit) && !sLimitPattern.matcher(limit).matches()) {
         throw new IllegalArgumentException("invalid LIMIT clauses:" + limit);
     }

     StringBuilder query = new StringBuilder(120);

     query.append("SELECT ");
     if (distinct) {
         query.append("DISTINCT ");
     }
     if (columns != null && columns.length != 0) {
         appendColumns(query, columns);
     } else {
         query.append(" * ");
     }
     query.append("FROM ");
     query.append(tables);
     appendClause(query, " WHERE ", where);
     appendClause(query, " GROUP BY ", groupBy);
     appendClause(query, " HAVING ", having);
     appendClause(query, " ORDER BY ", orderBy);
     appendClause(query, " LIMIT ", limit);
     return query.toString();
 }

 /**
  * Add the names that are non-null in columns to s, separating
  * them with commas.
  */
 private static void appendColumns(StringBuilder s, String[] columns) {
     int n = columns.length;

     for (int i = 0; i < n; i++) {
         String column = columns[i];

         if (column != null) {
             if (i > 0) {
                 s.append(", ");
             }
             s.append(column);
         }
     }
     s.append(' ');
 }

 /**
  * addClause
  *
  * @param s      the add StringBuilder
  * @param name   clauseName
  * @param clause clauseSelection
  */
 private static void appendClause(StringBuilder s, String name, String clause) {
     if (!isEmpty(clause)) {
         s.append(name);
         s.append(clause);
     }
 }

 /**
  * Returns true if the string is null or 0-length.
  *
  * @param str the string to be examined
  * @return true if str is null or zero length
  */
 private static boolean isEmpty(@Nullable CharSequence str) {
     if (str == null || str.length() == 0)
         return true;
     else
         return false;
 }

 /**
  * the pattern of limit
  */
 private static final Pattern sLimitPattern =
         Pattern.compile("\\s*\\d+\\s*(,\\s*\\d+\\s*)?");

 /**
  * After the execution of the complete SQL statement, not necessarily the actual implementation of the SQL statement
  *
  * @param sql      SQL statement
  * @param bindArgs Binding parameters
  * @return Replace? SQL statement executed after the
  */
 private static String getExecSQL(String sql, Object[] bindArgs) {
     StringBuilder sb = new StringBuilder(sql);
     if (bindArgs != null && bindArgs.length > 0) {
         int index = 0;
         for (int i = 0; i < bindArgs.length; i++) {
             index = sb.indexOf("?", index);
             sb.replace(index, index + 1, String.valueOf(bindArgs[i]));
         }
     }
     return sb.toString();
 }
}

九.用法

测试代码

import util.DBUtil;

import java.sql.SQLException;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
* Created by yuandl on 2016-12-16.
*/
public class DBTest {

public static void main(String[] args) {
    System.out.println("数据库的原数据");
    testQuery3();
    testInsert();
    System.out.println("执行插入后的数据");
    testQuery3();
    testUpdate();
    System.out.println("执行修改后的数据");
    testQuery3();
    testDelete();
    System.out.println("执行删除后的数据");
    testQuery3();
    System.out.println("带条件的查询1");
    testQuery2();
    System.out.println("带条件的查询2");
    testQuery1();
}



/**
 * 测试插入
 */
private static void testInsert() {
    Map<String, Object> map = new HashMap<>();
    map.put("emp_id", 1013);
    map.put("name", "JDBCUtil测试");
    map.put("job", "developer");
    map.put("salary", 10000);
    map.put("hire_date", new java.sql.Date(System.currentTimeMillis()));
    try {
        int count = DBUtil.insert("emp_test", map);
              } catch (SQLException e) {
        e.printStackTrace();
    }
}



/**
 * 测试更新
 */
private static void testUpdate() {
    Map<String, Object> map = new HashMap<>();
    map.put("name", "测试更新");

    Map<String, Object> whereMap = new HashMap<>();
    whereMap.put("emp_id", "1013");
    try {
        int count = DBUtil.update("emp_test", map, whereMap);
    } catch (SQLException e) {
        e.printStackTrace();
    }
}



/**
 * 测试删除
 */
private static void testDelete() {
    Map<String, Object> whereMap = new HashMap<>();
    whereMap.put("emp_id", 1013);
    whereMap.put("job", "developer");
    try {
        int count = DBUtil.delete("emp_test", whereMap);
    } catch (SQLException e) {
        e.printStackTrace();
    }
}
/**
 * 查询方式一
 */
public static void testQuery1() {
    Map<String,Object> whereMap=new HashMap<>();
    whereMap.put("salary","10000");
    try {
        DBUtil.query("emp_test",whereMap);
    } catch (SQLException e) {
        e.printStackTrace();
    }
}
/**
 * 查询方式二
 */
public static void testQuery2() {
    String where = "job = ?  AND salary = ? ";
    String[] whereArgs = new String[]{"clerk", "3000"};

    try {
        List<Map<String, Object>> list = DBUtil.query("emp_test", where, whereArgs);

    } catch (SQLException e) {
        e.printStackTrace();
    }
}

/**
 * 查询方式三
 */
public static void testQuery3() {
    try {
        List<Map<String, Object>> list = DBUtil.query("emp_test", false, null, null, null, null, null, null, null);

    } catch (SQLException e) {
        e.printStackTrace();
    }
}
}

打印结果

数据库的原数据
SELECT  * FROM emp_test
成功查询到了14行数据
第1行：{DEPT_TEST_ID=10, EMP_ID=1001, SALARY=10000, HIRE_DATE=2010-01-12, BONUS=2000, MANAGER=1005, JOB=Manager, NAME=张无忌}
第2行：{DEPT_TEST_ID=10, EMP_ID=1002, SALARY=8000, HIRE_DATE=2011-01-12, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=刘苍松}
第3行：{DEPT_TEST_ID=10, EMP_ID=1003, SALARY=9000, HIRE_DATE=2010-02-11, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=李翊}
第4行：{DEPT_TEST_ID=10, EMP_ID=1004, SALARY=5000, HIRE_DATE=2010-02-11, BONUS=null, MANAGER=1001, JOB=Programmer, NAME=郭芙蓉}
第5行：{DEPT_TEST_ID=20, EMP_ID=1005, SALARY=15000, HIRE_DATE=2008-02-15, BONUS=null, MANAGER=null, JOB=President, NAME=张三丰}
第6行：{DEPT_TEST_ID=20, EMP_ID=1006, SALARY=5000, HIRE_DATE=2009-02-01, BONUS=400, MANAGER=1005, JOB=Manager, NAME=燕小六}
第7行：{DEPT_TEST_ID=20, EMP_ID=1007, SALARY=3000, HIRE_DATE=2009-02-01, BONUS=500, MANAGER=1006, JOB=clerk, NAME=陆无双}
第8行：{DEPT_TEST_ID=30, EMP_ID=1008, SALARY=5000, HIRE_DATE=2009-05-01, BONUS=500, MANAGER=1005, JOB=Manager, NAME=黄蓉}
第9行：{DEPT_TEST_ID=30, EMP_ID=1009, SALARY=4000, HIRE_DATE=2009-02-20, BONUS=null, MANAGER=1008, JOB=salesman, NAME=韦小宝}
第10行：{DEPT_TEST_ID=30, EMP_ID=1010, SALARY=4500, HIRE_DATE=2009-05-10, BONUS=500, MANAGER=1008, JOB=salesman, NAME=郭靖}
第11行：{DEPT_TEST_ID=null, EMP_ID=1011, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=于泽成}
第12行：{DEPT_TEST_ID=null, EMP_ID=1012, SALARY=null, HIRE_DATE=2011-08-10, BONUS=null, MANAGER=null, JOB=null, NAME=amy}
第13行：{DEPT_TEST_ID=null, EMP_ID=1014, SALARY=8000, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=张无忌}
第14行：{DEPT_TEST_ID=20, EMP_ID=1015, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=刘苍松}

INSERT INTO emp_test (name,hire_date,job,salary,emp_id )  VALUES (JDBCUtil测试,2016-12-17,developer,10000,1013 )
成功新增了1行

执行插入后的数据
SELECT  * FROM emp_test
成功查询到了15行数据
第1行：{DEPT_TEST_ID=10, EMP_ID=1001, SALARY=10000, HIRE_DATE=2010-01-12, BONUS=2000, MANAGER=1005, JOB=Manager, NAME=张无忌}
第2行：{DEPT_TEST_ID=10, EMP_ID=1002, SALARY=8000, HIRE_DATE=2011-01-12, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=刘苍松}
第3行：{DEPT_TEST_ID=10, EMP_ID=1003, SALARY=9000, HIRE_DATE=2010-02-11, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=李翊}
第4行：{DEPT_TEST_ID=10, EMP_ID=1004, SALARY=5000, HIRE_DATE=2010-02-11, BONUS=null, MANAGER=1001, JOB=Programmer, NAME=郭芙蓉}
第5行：{DEPT_TEST_ID=20, EMP_ID=1005, SALARY=15000, HIRE_DATE=2008-02-15, BONUS=null, MANAGER=null, JOB=President, NAME=张三丰}
第6行：{DEPT_TEST_ID=20, EMP_ID=1006, SALARY=5000, HIRE_DATE=2009-02-01, BONUS=400, MANAGER=1005, JOB=Manager, NAME=燕小六}
第7行：{DEPT_TEST_ID=20, EMP_ID=1007, SALARY=3000, HIRE_DATE=2009-02-01, BONUS=500, MANAGER=1006, JOB=clerk, NAME=陆无双}
第8行：{DEPT_TEST_ID=30, EMP_ID=1008, SALARY=5000, HIRE_DATE=2009-05-01, BONUS=500, MANAGER=1005, JOB=Manager, NAME=黄蓉}
第9行：{DEPT_TEST_ID=30, EMP_ID=1009, SALARY=4000, HIRE_DATE=2009-02-20, BONUS=null, MANAGER=1008, JOB=salesman, NAME=韦小宝}
第10行：{DEPT_TEST_ID=30, EMP_ID=1010, SALARY=4500, HIRE_DATE=2009-05-10, BONUS=500, MANAGER=1008, JOB=salesman, NAME=郭靖}
第11行：{DEPT_TEST_ID=null, EMP_ID=1011, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=于泽成}
第12行：{DEPT_TEST_ID=null, EMP_ID=1012, SALARY=null, HIRE_DATE=2011-08-10, BONUS=null, MANAGER=null, JOB=null, NAME=amy}
第13行：{DEPT_TEST_ID=null, EMP_ID=1014, SALARY=8000, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=张无忌}
第14行：{DEPT_TEST_ID=20, EMP_ID=1015, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=刘苍松}
第15行：{DEPT_TEST_ID=null, EMP_ID=1013, SALARY=10000, HIRE_DATE=2016-12-17, BONUS=null, MANAGER=null, JOB=developer, NAME=JDBCUtil测试}

UPDATE emp_test SET name = 测试更新  WHERE emp_id = 1013 
成功修改了1行

执行修改后的数据
SELECT  * FROM emp_test
成功查询到了15行数据
第1行：{DEPT_TEST_ID=10, EMP_ID=1001, SALARY=10000, HIRE_DATE=2010-01-12, BONUS=2000, MANAGER=1005, JOB=Manager, NAME=张无忌}
第2行：{DEPT_TEST_ID=10, EMP_ID=1002, SALARY=8000, HIRE_DATE=2011-01-12, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=刘苍松}
第3行：{DEPT_TEST_ID=10, EMP_ID=1003, SALARY=9000, HIRE_DATE=2010-02-11, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=李翊}
第4行：{DEPT_TEST_ID=10, EMP_ID=1004, SALARY=5000, HIRE_DATE=2010-02-11, BONUS=null, MANAGER=1001, JOB=Programmer, NAME=郭芙蓉}
第5行：{DEPT_TEST_ID=20, EMP_ID=1005, SALARY=15000, HIRE_DATE=2008-02-15, BONUS=null, MANAGER=null, JOB=President, NAME=张三丰}
第6行：{DEPT_TEST_ID=20, EMP_ID=1006, SALARY=5000, HIRE_DATE=2009-02-01, BONUS=400, MANAGER=1005, JOB=Manager, NAME=燕小六}
第7行：{DEPT_TEST_ID=20, EMP_ID=1007, SALARY=3000, HIRE_DATE=2009-02-01, BONUS=500, MANAGER=1006, JOB=clerk, NAME=陆无双}
第8行：{DEPT_TEST_ID=30, EMP_ID=1008, SALARY=5000, HIRE_DATE=2009-05-01, BONUS=500, MANAGER=1005, JOB=Manager, NAME=黄蓉}
第9行：{DEPT_TEST_ID=30, EMP_ID=1009, SALARY=4000, HIRE_DATE=2009-02-20, BONUS=null, MANAGER=1008, JOB=salesman, NAME=韦小宝}
第10行：{DEPT_TEST_ID=30, EMP_ID=1010, SALARY=4500, HIRE_DATE=2009-05-10, BONUS=500, MANAGER=1008, JOB=salesman, NAME=郭靖}
第11行：{DEPT_TEST_ID=null, EMP_ID=1011, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=于泽成}
第12行：{DEPT_TEST_ID=null, EMP_ID=1012, SALARY=null, HIRE_DATE=2011-08-10, BONUS=null, MANAGER=null, JOB=null, NAME=amy}
第13行：{DEPT_TEST_ID=null, EMP_ID=1014, SALARY=8000, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=张无忌}
第14行：{DEPT_TEST_ID=20, EMP_ID=1015, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=刘苍松}
第15行：{DEPT_TEST_ID=null, EMP_ID=1013, SALARY=10000, HIRE_DATE=2016-12-17, BONUS=null, MANAGER=null, JOB=developer, NAME=测试更新}

DELETE FROM emp_test WHERE job = developer  AND emp_id = 1013 
成功删除了1行

执行删除后的数据
SELECT  * FROM emp_test
成功查询到了14行数据
第1行：{DEPT_TEST_ID=10, EMP_ID=1001, SALARY=10000, HIRE_DATE=2010-01-12, BONUS=2000, MANAGER=1005, JOB=Manager, NAME=张无忌}
第2行：{DEPT_TEST_ID=10, EMP_ID=1002, SALARY=8000, HIRE_DATE=2011-01-12, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=刘苍松}
第3行：{DEPT_TEST_ID=10, EMP_ID=1003, SALARY=9000, HIRE_DATE=2010-02-11, BONUS=1000, MANAGER=1001, JOB=Analyst, NAME=李翊}
第4行：{DEPT_TEST_ID=10, EMP_ID=1004, SALARY=5000, HIRE_DATE=2010-02-11, BONUS=null, MANAGER=1001, JOB=Programmer, NAME=郭芙蓉}
第5行：{DEPT_TEST_ID=20, EMP_ID=1005, SALARY=15000, HIRE_DATE=2008-02-15, BONUS=null, MANAGER=null, JOB=President, NAME=张三丰}
第6行：{DEPT_TEST_ID=20, EMP_ID=1006, SALARY=5000, HIRE_DATE=2009-02-01, BONUS=400, MANAGER=1005, JOB=Manager, NAME=燕小六}
第7行：{DEPT_TEST_ID=20, EMP_ID=1007, SALARY=3000, HIRE_DATE=2009-02-01, BONUS=500, MANAGER=1006, JOB=clerk, NAME=陆无双}
第8行：{DEPT_TEST_ID=30, EMP_ID=1008, SALARY=5000, HIRE_DATE=2009-05-01, BONUS=500, MANAGER=1005, JOB=Manager, NAME=黄蓉}
第9行：{DEPT_TEST_ID=30, EMP_ID=1009, SALARY=4000, HIRE_DATE=2009-02-20, BONUS=null, MANAGER=1008, JOB=salesman, NAME=韦小宝}
第10行：{DEPT_TEST_ID=30, EMP_ID=1010, SALARY=4500, HIRE_DATE=2009-05-10, BONUS=500, MANAGER=1008, JOB=salesman, NAME=郭靖}
第11行：{DEPT_TEST_ID=null, EMP_ID=1011, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=于泽成}
第12行：{DEPT_TEST_ID=null, EMP_ID=1012, SALARY=null, HIRE_DATE=2011-08-10, BONUS=null, MANAGER=null, JOB=null, NAME=amy}
第13行：{DEPT_TEST_ID=null, EMP_ID=1014, SALARY=8000, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=张无忌}
第14行：{DEPT_TEST_ID=20, EMP_ID=1015, SALARY=null, HIRE_DATE=null, BONUS=null, MANAGER=null, JOB=null, NAME=刘苍松}

带条件的查询1
SELECT  * FROM emp_test WHERE job = clerk  AND salary = 3000 
成功查询到了1行数据
第1行：{DEPT_TEST_ID=20, EMP_ID=1007, SALARY=3000, HIRE_DATE=2009-02-01, BONUS=500, MANAGER=1006, JOB=clerk, NAME=陆无双}

带条件的查询2
SELECT  * FROM emp_test WHERE salary = 10000 
成功查询到了1行数据
第1行：{DEPT_TEST_ID=10, EMP_ID=1001, SALARY=10000, HIRE_DATE=2010-01-12, BONUS=2000, MANAGER=1005, JOB=Manager, NAME=张无忌}

十.GitHub