我期待在我的整个应用程序中使用singleton jdbc连接。 使用我的下面的编码，当我开始我的tomcat从数据库获取数据后，在某个时间后，我得到低于异常。 我没有得到什么问题，任何人都可以提出可能的原因。
例外：
com.mysql.cj.jdbc.exceptions.CommunicationsException: The last packet successfully received from the server was 65,128,558 milliseconds ago. The last packet sent succ$
at com.mysql.cj.jdbc.exceptions.SQLError.createCommunicationsException(SQLError.java:615)
at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:57)
at com.mysql.cj.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2011)
at com.mysql.cj.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1826)
at com.mysql.cj.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:1923)
at com.pradeep.sms.db.DBDataAccess.getDropdown(DBDataAccess.java:25)
at com.pradeep.sms.controller.WebServicesController.getDropdown(WebServicesController.java:35)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory$1.invoke(ResourceMethodInvocationHandlerFactory.java:81)
at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:144)
at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:161)
at org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$ResponseOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:160)
at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:99)
at org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:389)
at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:347)
at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:102)
at org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:326)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:305)
at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1154)
at org.glassfish.jersey.servlet.WebComponent.serviceImpl(WebComponent.java:473)
at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:427)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:388)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:341)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:228)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
单身人士课程
public class DBConnection {
private static String DB_DRIVER = "com.mysql.cj.jdbc.Driver";
private static String DB_USER = "pradeep";
private static String DB_PASSWORD = "12345678";
private static String DB_NAME = "edusoft";
private static String HOSTNAME = "host";
private static String DB_PORT = "3306";
private static String DB_CONNECTION = "jdbc:mysql://" + HOSTNAME + ":" + DB_PORT + "/" + DB_NAME + "?user="
+ DB_USER + "&password=" + DB_PASSWORD;
private static final DBConnection ONLY_ONE = new DBConnection();
private Connection con;
private DBConnection() {
try {
Class.forName(DB_DRIVER);
con = DriverManager.getConnection(DB_CONNECTION);// SQLException
} catch (ClassNotFoundException | SQLException e) {
e.printStackTrace();
}
}
public static DBConnection getInstance() {
return ONLY_ONE;
}
public Connection getcon() {
return con;
}
}
我的申请类
private Connection connection = DBConnection.getInstance().getcon();
public String getDropdown(String dropdownName ) {
String proCall="{call getDropdown(?)}";
JSONObject jSONObject = new JSONObject();
ArrayList<String> result = new ArrayList<String>();
try {
preparedStatement = connection.prepareStatement(proCall);
preparedStatement.setString(1, dropdownName);
resultSet= preparedStatement.executeQuery();
while (resultSet.next()) {
String classNames = resultSet.getString(1);
result.add(classNames);
}
JSONArray jsArray = new JSONArray(result);
jSONObject.put("rs", jsArray);
} catch (SQLException e) {
e.printStackTrace();
}finally{
if(resultSet!=null)
try {
resultSet.close();
} catch (SQLException e1) {
e1.printStackTrace();
}
if(preparedStatement !=null){
try {
preparedStatement.close();
} catch (Exception e2) {
}
}
}
return jSONObject.toString();
}
答案 0 :(得分：-1)
服务器未启动或主机错误。检查服务器状态和您在代码中提供的主机名