［打造自己的代码库］ConnectionUtil

import java.math.BigDecimal;
import java.sql.Connection;
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;

/**
* 此为java.sql.Connection 的工具类。
* 用意：为了更方便的使用jdbc操作数据库。
*
* @author JZZ 2016-06-29
* modify 2016-10-20
*
*/
public class ConnectionUtil{
/**
* 功能：使用prepareStatement(...)执行查询
* 注意事项：querySql内的占位符 必须与paramArray的参数一致。
* @throws Exception
*/
public static List<Map<String,Object>> executeQuery(Connection conn,String querySql,Object[] paramArray) throws Exception{
PreparedStatement stmt = null;
ResultSet rs = null;
List<Map<String,Object>> resultList = null;
try{
stmt = conn.prepareStatement(querySql.toString(),ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
setStmtParam(stmt,paramArray);
rs = stmt.executeQuery();
resultList = fromResultSetToList(rs);
}catch(Exception e){
e.printStackTrace();
throw e;
}finally{
close(stmt);
}
return resultList;
}
public static Integer executeUpdate(Connection conn, String insertSql, Object[] paramArray) throws Exception {
PreparedStatement stmt = null;
Integer affectCount = 0;
try{
stmt = conn.prepareStatement(insertSql.toString(),ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
setStmtParam(stmt,paramArray);
affectCount = stmt.executeUpdate();
}catch(Exception e){
e.printStackTrace();
throw e;
}finally{
close(stmt);
}
return affectCount;
}
public static void close(PreparedStatement stmt) throws SQLException {
if(stmt!=null && !stmt.isClosed()){
stmt.close();
}
}
public static void close(Connection conn) throws SQLException {
if(conn!=null && !conn.isClosed()){
conn.close();
}
}

/**
* 功能：读取 ResultSet 到 List<Map<String, Object>>
* 需设置 ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY
* @param rs
* @return
* @throws SQLException
*/
public static List<Map<String, Object>> fromResultSetToList(ResultSet rs) throws SQLException {
int rows = 0;
int colmns = 0;
ResultSetMetaData metaData = null;
List<Map<String, Object>> resultList ;
Map<String,Object> rowsMap ;
try {
rs.last();
rows = rs.getRow();
rs.beforeFirst();
resultList = new ArrayList<Map<String, Object>>(rows);
metaData = rs.getMetaData();
colmns = metaData.getColumnCount();

while(rs.next()){// 遍历每一行
rowsMap = new HashMap<String,Object>();
for(int i=1; i<=colmns; i++){
rowsMap.put(metaData.getColumnName(i), rs.getObject(i));
}
resultList.add(rowsMap);
}
return resultList;
} catch (SQLException e) {
e.printStackTrace();
throw(e);
}
}
/**
* 功能：为stmt填充参数
* @param stmt
* @param array 参数数组，
* @throws Exception
*/
public static void setStmtParam(PreparedStatement stmt, Object[] array) throws Exception {
if(array == null){
return ;
}
for(int i=0; i<array.length; i++){
setStmtParam(stmt, i+1, array[i]);
}
}
/**
* 功能：为stmt填充参数
* 若新增类型 需扩充if else
* @param stmt
* @param i 从1计数
* @param object
* @throws Exception
*/
public static void setStmtParam(PreparedStatement stmt, int i, Object object) throws Exception {
if(object.getClass() == String.class){
stmt.setString(i, (String) object);
}else if(object.getClass() == Double.class){
stmt.setDouble(i, (Double) object);
}else if(object.getClass() == Long.class){
stmt.setLong(i, (Long) object);
}else if(object.getClass() == BigDecimal.class){
stmt.setBigDecimal(1, (BigDecimal) object);
}else{
stmt.setObject(i, object);
//          throw new Exception(" 不识别的类型 in setStmtParam(...)  ");
}
}

}