如何解决如何从Java应用程序创建mysql持久连接？
| 嗨，我正在编写一个Java应用程序，该应用程序需要与mysql数据库创建持久连接。我无权访问数据库服务器，因此我无法更改数据库服务器上的任何内容，因此它不会关闭连接。 我收到以下错误：Exception in thread \"main\" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure
The last packet successfully received from the server was 368,140 milliseconds ago. The last packet sent successfully to the server was 366,869 milliseconds ago.
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:409)
at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1118)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3055)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2941)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3489)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2113)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2568)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2113)
at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2275)
at SearchAndUpdate.recursiveUpdate(SearchAndUpdate.java:101)
at SearchAndUpdate.recursiveUpdate(SearchAndUpdate.java:110)
at SearchAndUpdate.recursiveUpdate(SearchAndUpdate.java:110)
at SearchAndUpdate.recursiveUpdate(SearchAndUpdate.java:110)
at SearchAndUpdate.recursiveUpdate(SearchAndUpdate.java:110)
at SearchAndUpdate.recursiveUpdate(SearchAndUpdate.java:110)
at SearchAndUpdate.recursiveUpdate(SearchAndUpdate.java:110)
at SearchAndUpdate.recursiveUpdate(SearchAndUpdate.java:110)
at SearchAndUpdate.recursiveTraversal(SearchAndUpdate.java:55)
at SearchAndUpdate.main(SearchAndUpdate.java:40)
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(Unknown Source)
at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:114)
at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:161)
at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:189)
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:2499)
at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2952)
... 17 more
import java.sql.*;
public class Connect
{
public static void main (String[] args)
{
Connection conn = null;
try
{
String userName = \"sdfasdfsf\";
String password = \"asdfasdfsd\";
String url = \"jdbc:mysql://nameOfcomputer:3306/databasename\";
Class.forName (\"com.mysql.jdbc.Driver\").newInstance();
conn = DriverManager.getConnection (url,userName,password);
System.out.println (\"Database connection established\");
}
catch (Exception e)
{
System.err.println (\"Cannot connect to database server\");
System.out.println(e.getMessage());
}
}
}
public class Search{
public static void main(String[] args) throws SQLException
{
File fileObject = new File(\"scanLocation\");
Connection conn = getConnection();
update(fileObject,conn);
conn.close();
}
public static void update(File fileObject,Connection conn)throws SQLException
{
if (fileObject.isDirectory())
{
File allFiles[] = fileObject.listFiles();
if (allFiles != null)
{
for (File aFile : allFiles)
{
if (aFile.isFile())
{
String filename=aFile.aFile.getName();
String query = \"INSERT INTO table(\"
+ \"File_Name\" +\")\"
+ \" Values (?)\";
try
{ PreparedStatement psmt=conn.prepareStatement(query);
psmt.setString(1,fileName);
psmt.executeUpdate();
}
catch (SQLException e)
{
System.out.println(\"SQLExceptoin - \" + e.getMessage());
System.out.println(\"SQLState: \" + e.getSQLState());
System.out.println(\"VendorError: \" + e.getErrorCode());
e.printStackTrace();
}
}
else
{
recursiveUpdate(aFile,conn);
}
}
}
}
}
public static Connection getConnection()
{
String DATABASE_USER = \"user\";
String DATABASE_PASSWORD = \"password\";
String MYSQL_AUTO_RECONNECT = \"autoReconnect\";
String MYSQL_MAX_RECONNECTS = \"maxReconnects\";
Connection conn = null;
try
{
String userName = \"username\";
String password = \"password\";
String url = \"jdbc:mysql://compName:3306/database\";
Class.forName(\"com.mysql.jdbc.Driver\").newInstance();
conn = DriverManager.getConnection(url,password);
java.util.Properties connProperties = new java.util.Properties();
connProperties.put(DATABASE_USER,userName);
connProperties.put(DATABASE_PASSWORD,password);
connProperties.put(MYSQL_AUTO_RECONNECT,\"true\");
connProperties.put(MYSQL_MAX_RECONNECTS,\"4\");
return DriverManager.getConnection(url,connProperties);
}
catch (Exception e)
{
System.err.println(\"Cannot connect to database server\");
System.out.println(e.getMessage());
e.printStackTrace();
}
return conn;
}
}
解决方法
好吧，如果您无法控制服务器关闭连接的时间，那么您将不得不打开一个新连接。在这种情况下，您将无法建立真正的持久连接（尽管您可以为其中一个创建外观）-您将必须检测到该外观已关闭并重新打开一个新外观。
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