在这里,我使用 jdbcHelper 建立与数据库的连接,但有时(不是所有时间)我在连接建立时收到异常作为空指针,但并非总是如此。这是我的代码。此代码用于将数据插入数据库..
Connection conn = JDBCHelper.getConnection();
PreparedStatement ps1 = null;
System.out.println("In Side DATA BASE");
System.out.println("in side database deviceid=" + s);
System.out.println("in side database rfide=" + s1);
System.out.println("in side database longitude=" + lati);
System.out.println("in side database latitude= " + lot);
System.out.println("in side database datalength=" + data_length);
Date date = new Date();
java.sql.Timestamp dt = new java.sql.Timestamp(date.getTime());
int flag = 1;
System.out.println("date=" + dt);
System.out.println("flag=" + flag);
try {
String hql = "insert into gpsData1(dateTime,deviceid,latitude,longitude,rfid,flag,datalength) values(?,?,?,?,?,?,?)";
ps1 = conn.prepareStatement(hql);
ps1.setString(1, dt.toString());
ps1.setString(2, s);
ps1.setFloat(3, lati);
ps1.setFloat(4, lot);
ps1.setString(5, s1);
ps1.setInt(6, flag);
ps1.setInt(7, data_length);
ps1.executeUpdate();
conn.commit();
System.out.println("DATA BASE Inserting Completed");
} catch (Exception ex) {
ex.printStackTrace();
} finally {
JDBCHelper.close(ps1);
JDBCHelper.close(conn);
}
这是我的 JDBC 代码..
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class JDBCHelper {
public static final String url = "jdbc:mysql://localhost:3306/treamisdemo";
public static final String uid = "root";
public static final String pwd = "myserver";
/**
* @param
* args
*/
static {
try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("connection is sucessful");
} catch (ClassNotFoundException e) {
System.err.println("ERROR: failed to load mysql JDBC driver.");
e.printStackTrace();
}
}
public static void close(ResultSet c) {
try {
if (c != null) {
c.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
public static void close(Statement c) {
try {
if (c != null) {
c.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
public static void close(Connection c) {
try {
if (c != null) {
c.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
public static Connection getConnection() {
Connection con = null;
try {
con = DriverManager.getConnection(url, uid, pwd);
System.out.println("obtain connection =" + con);
con.setAutoCommit(false);
return con;
} catch (SQLException e) {
e.printStackTrace();
return null;
}
}
}
这是堆栈跟踪..
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Data sourc
e rejected establishment of connection, message from server: "Too many connecti
ons"
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstruct
orAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingC
onstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.Util.getInstance(Util.java:386)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1013)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1128)
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2336)
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2
369)
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2153)
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:792)
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47)
at sun.reflect.GeneratedConstructorAccessor39.newInstance(Unknown Source
)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingC
onstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java
:305)
at java.sql.DriverManager.getConnection(DriverManager.java:571)
at java.sql.DriverManager.getConnection(DriverManager.java:215)
at com.treamis.transport.vehicle.JDBCHelper.getConnection(JDBCHelper.jav
a:71)
at com.treamis.transport.vehicle.MyTimerTask.getRoutePointList(MyTimerTa
sk.java:639)
at com.treamis.transport.vehicle.MyTimerTask.sendSms(MyTimerTask.java:10
8)
at com.treamis.transport.vehicle.MyTimerTask.run(MyTimerTask.java:71)
at java.util.TimerThread.mainLoop(Timer.java:555)
at java.util.TimerThread.run(Timer.java:505)