JDBC实现纵向导出数据库数据

使用到的技术点：

1.Java写文件；

2.熟悉JDBC API;

3.Java集合ArrayList的使用；

4.Java字符串截取;

本代码仅供测试，如要使用，需自行增加数据库列类型定义和判定逻辑。

DBConnectMySQL.java

package com.manny.util.db;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class DBConnectMySQL {
private static String userName = "root";
private static String password = "123456";
private static String driver = "com.mysql.jdbc.Driver";

public Connection getConnection()
{
Connection conn = null;
try {
Class.forName(driver);

String url = "jdbc:mysql://localhost:3306/life";
conn = DriverManager.getConnection(url, userName, password);

} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
return conn;
}
}

ExportLongitudinalData.java

package com.manny.util;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import com.manny.db.common.DataTypeConstant;
import com.manny.util.db.DBConnectMySQL;

public class ExportLongitudinalData
{

public static void main(String[] args)
{

DBConnectMySQL cm = new DBConnectMySQL();

Connection conn = null;
Statement sts = null;
ResultSet rs = null;
try
{
conn = cm.getConnection();
sts = conn.createStatement();

String sql = "select * from life.pictures";
rs = sts.executeQuery(sql);

ResultSetMetaData rsmd = rs.getMetaData();

int colCount = rsmd.getColumnCount();

System.out.println("colCount=" + colCount);

List colNameAndDatas = new ArrayList();

for (int i = 1; i <= colCount; i++)
{

String colTypeName = rsmd.getColumnTypeName(i);
String colClassName = rsmd.getColumnClassName(i);

String colName = rsmd.getColumnName(i);

colNameAndDatas.add(colName);
}

while (rs.next())
{

for (int i = 1; i <= colCount; i++)
{

String colTypeName = rsmd.getColumnTypeName(i);

String colData = getColumnData(rs, i, colTypeName);

String currentData = (String) colNameAndDatas.get(i - 1);

colNameAndDatas.set(i - 1, currentData + "," + colData);
}

}
String fileName = getTableNameFromSQL(sql, "CSV");
outputToFile(colNameAndDatas, fileName);

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

finally
{
try
{
if (rs != null && !rs.isClosed())
rs.close();
if (sts != null && !sts.isClosed())
sts.close();
if (conn != null && !conn.isClosed())
conn.close();
}
catch (SQLException e)
{
e.printStackTrace();
}
}

}

private static String getColumnData(ResultSet rs, int columnIndex, String colTypeName)
{
try
{
if (DataTypeConstant.TYPE_VARCHAR.equals(colTypeName))
{
return rs.getString(columnIndex);
}
if (DataTypeConstant.TYPE_CHAR.equals(colTypeName))
{
return rs.getString(columnIndex);
}
}
catch (SQLException e)
{
e.printStackTrace();
}
return "";
}

private static void outputToFile(List rowDataList, String fileName)
{
try
{
String filePath = "D:\\temp\\";
File dir = new File(filePath);
if (!dir.exists())
{
dir.mkdirs();
}
File exportFile = new File(filePath + File.separator + fileName);
if (!exportFile.exists())
{
exportFile.createNewFile();
}

FileWriter fw = new FileWriter(exportFile);

for (Iterator iterator = rowDataList.iterator(); iterator.hasNext();)
{
String rowData = (String) iterator.next();
System.out.println(rowData);

fw.write(rowData + "\n");
}
fw.flush();
fw.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}

private static String getTableNameFromSQL(String sql, String fileExt)
{
String fileName = "";
if (sql != null)
{
sql = sql.toUpperCase().trim();
int whInd = sql.indexOf(" WHERE ");
int frmInd = sql.indexOf(" FROM ");
int ordInd = sql.indexOf(" ORDER BY ");
if (frmInd == -1)
{
fileName = "ErrorSQL";
}
frmInd+=5;
if (whInd > 0)
{
fileName = sql.substring(frmInd, whInd).trim();
}
else if (ordInd > 0)
{
fileName = sql.substring(frmInd, ordInd).trim();
}
else
{
fileName = sql.substring(frmInd).trim();
}
}
return fileName + "." + fileExt;
}

}

DataTypeConstant.java

package com.manny.db.common;
public interface DataTypeConstant
{
public static String TYPE_VARCHAR="VARCHAR";
public static String TYPE_CHAR="CHAR";
}