Java获取数据库各种查询结果_MySQL

在查询时候有时候要一条数据，有时候要的是一个结果集，然而有时候返回就是一个统计值，通过对ResultSet和ResultSetMetaData的变换得到各类所需的查询结果，因为没有利用连接池数据链接管理比较麻烦，所以谢了一个工具类，

package com.sky.connect;import java.lang.reflect.InvocationTargetException;import java.sql.ResultSet;import java.sql.SQLException;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import org.apache.commons.beanutils.BeanUtils;import com.mysql.jdbc.Connection;import com.mysql.jdbc.PreparedStatement;import com.mysql.jdbc.ResultSetMetaData;/** * DAO设计模式 *  * @author 潘琢文 *  */public class DAO {  /**  * 更新数据库操作   *   * @param sql    * @param args   */ public void update(String sql, Object... args) {        Connection connection = null;       PreparedStatement preparedStatement = null;     try {           connection = JDBCTools.getConnection();         preparedStatement = (PreparedStatement) connection                  .prepareStatement(sql);         for (int i = 0; i  T get(Class<t> clazz, String sql, Object... args) {        T entity = null;        Connection connection = null;       PreparedStatement preparedStatement = null;     ResultSet result = null;        try {           connection = JDBCTools.getConnection();         preparedStatement = (PreparedStatement) connection                  .prepareStatement(sql);         for (int i = 0; i  map = new HashMap<string object>();            ResultSetMetaData rsmd = (ResultSetMetaData) result.getMetaData();          if (result.next()) {                for (int i = 0; i  0) {             entity = clazz.newInstance();               for (Map.Entry<string object> entry : map.entrySet()) {                   String filedName = entry.getKey();                  Object filedObject = entry.getValue();                  BeanUtils.setProperty(entity, filedName, filedObject);              }           }       } catch (Exception e) {         e.printStackTrace();        } finally {         JDBCTools.release(result, preparedStatement, connection);       }       return entity;  }   /**  * 通用查询方法，返回一个结果集    *   * @param clazz  * @param sql    * @param args   * @return   */ public <t> List<t> getForList(Class<t> clazz, String sql, Object... args) {       List<t> list = new ArrayList<t>();      Connection connection = null;       PreparedStatement preparedStatement = null;     ResultSet result = null;        try {           connection = JDBCTools.getConnection();         preparedStatement = (PreparedStatement) connection                  .prepareStatement(sql);         for (int i = 0; i > values = handleResultSetToMapList(result);           list = transfterMapListToBeanList(clazz, values);       } catch (Exception e) {         e.printStackTrace();        } finally {         JDBCTools.release(result, preparedStatement, connection);       }       return list;    }   /**  *   * @param clazz  * @param values     * @return   * @throws InstantiationException    * @throws IllegalAccessException    * @throws InvocationTargetException     */ public <t> List<t> transfterMapListToBeanList(Class<t> clazz,         List<map object>> values) throws InstantiationException,           IllegalAccessException, InvocationTargetException {     List<t> result = new ArrayList<t>();        T bean = null;      if (values.size() > 0) {         for (Map<string object> m : values) {             bean = clazz.newInstance();             for (Map.Entry<string object> entry : m.entrySet()) {                 String propertyName = entry.getKey();                   Object value = entry.getValue();                    BeanUtils.setProperty(bean, propertyName, value);               }               // 13. 把 Object 对象放入到 list 中.               result.add(bean);           }       }       return result;  }   /**  *   * @param resultSet  * @return   * @throws SQLException  */ public List<map object>> handleResultSetToMapList(         ResultSet resultSet) throws SQLException {      List<map object>> values = new ArrayList<map object>>();      List<string> columnLabels = getColumnLabels(resultSet);       Map<string object> map = null;        while (resultSet.next()) {          map = new HashMap<string object>();           for (String columnLabel : columnLabels) {               Object value = resultSet.getObject(columnLabel);                map.put(columnLabel, value);            }           values.add(map);        }       return values;  }   /**  *   * @param resultSet  * @return   * @throws SQLException  */ private List<string> getColumnLabels(ResultSet resultSet)         throws SQLException {       List<string> labels = new ArrayList<string>();      ResultSetMetaData rsmd = (ResultSetMetaData) resultSet.getMetaData();       for (int i = 0; i  E getForValue(String sql, Object... args) {      Connection connection = null;       PreparedStatement preparedStatement = null;     ResultSet resultSet = null;     try {           connection = JDBCTools.getConnection();         preparedStatement = (PreparedStatement) connection                  .prepareStatement(sql);         for (int i = 0; i <br><pre class="brush:php;toolbar:false">package com.sky.connect;import java.io.IOException;import java.io.InputStream;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.util.Properties;import com.mysql.jdbc.Connection;import com.mysql.jdbc.Driver;import com.mysql.jdbc.PreparedStatement;import com.mysql.jdbc.Statement;/** * JDBC操作的工具类 版本 1.0 *  * @author 潘琢文 *  */public class JDBCTools {  /**  * 使用preparedStatement进行数据更新     *   * @param sql    * @param args   */ public static void update(String sql, Object ... args) {        Connection connection = null;       PreparedStatement preparedStatement = null;     try {           connection = JDBCTools.getConnection();         preparedStatement = (PreparedStatement) connection                  .prepareStatement(sql);         for (int i = 0; i <br>