问题
I'm using Tomcat 7, MySql Workbench 5.2.27, JSF 2.0 and this exception comes from the ManagedBean(TripTableBean.java) of my web page(Trip Record.xhtml). It comes up whenever I click to go to Trip Record.xhtml after navigating through my other web pages. Pardon my horrible codes...
TripTableBean.java
org.apache.tomcat.dbcp.dbcp.SQLNestedException: Cannot get a connection, pool error Timeout waiting for idle object
at org.apache.tomcat.dbcp.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:114)
at org.apache.tomcat.dbcp.dbcp.BasicDataSource.getConnection(BasicDataSource.java:1044)
at Database.DBController.readRequest(DBController.java:21)
at Database.TripTableBean.retrieve(TripTableBean.java:389)
at Database.TripTableBean.<init>(TripTableBean.java:69)
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 java.lang.Class.newInstance0(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at com.sun.faces.mgbean.BeanBuilder.newBeanInstance(BeanBuilder.java:188)
at com.sun.faces.mgbean.BeanBuilder.build(BeanBuilder.java:102)
at com.sun.faces.mgbean.BeanManager.createAndPush(BeanManager.java:409)
at com.sun.faces.mgbean.BeanManager.create(BeanManager.java:269)
at com.sun.faces.el.ManagedBeanELResolver.resolveBean(ManagedBeanELResolver.java:244)
at com.sun.faces.el.ManagedBeanELResolver.getValue(ManagedBeanELResolver.java:116)
at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:176)
at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:203)
at org.apache.el.parser.AstIdentifier.getValue(AstIdentifier.java:71)
at org.apache.el.parser.AstValue.getTarget(AstValue.java:94)
at org.apache.el.parser.AstValue.getType(AstValue.java:82)
at org.apache.el.ValueExpressionImpl.getType(ValueExpressionImpl.java:176)
at com.sun.faces.facelets.el.TagValueExpression.getType(TagValueExpression.java:98)
at org.primefaces.component.datatable.DataTable.isLazy(DataTable.java:904)
at org.primefaces.component.datatable.DataTableRenderer.encodeMarkup(DataTableRenderer.java:177)
at org.primefaces.component.datatable.DataTableRenderer.encodeEnd(DataTableRenderer.java:103)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:875)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1763)
at javax.faces.render.Renderer.encodeChildren(Renderer.java:168)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:845)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1756)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1759)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1759)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:401)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:131)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:121)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:594)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:405)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:964)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:515)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:304)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
The method where the exception originates : (TripTableBean.java:389) points to rs2 = db.readRequest(dbQuery2);
public void retrieve() throws SQLException, NamingException {
t = new ArrayList<TripSearchy>();
ResultSet rs = null;
ResultSet rs2 = null;
ResultSet rs3 = null;
DBController db = new DBController();
db.setUp();
//SQL: change select statement here
String dbQuery = "select * from (trip inner join agency on trip.id=agency.trip_id inner join tourguide on trip.id=tourguide.trip_id inner join accommodation on trip.id=accommodation.trip_id)";
rs = db.readRequest(dbQuery);
try{
while(rs.next()){
//add to list
id = rs.getInt("trip.id");
name = rs.getString("trip.name");
startDate = rs.getString("trip.startDate");
endDate = rs.getString("trip.endDate");
costOfTrip = rs.getString("trip.costOfTrip");
maxNoOfParticipants = rs.getString("trip.maxNoOfParticipants");
closingDateOfApplication = rs.getString("trip.closingDateOfApplication");
instructions = rs.getString("trip.instructions");
psea = rs.getString("trip.psea");
fasop = rs.getString("trip.fasop");
ktpiop = rs.getString("trip.ktpiop");
opId = rs.getInt("trip.overseasprogramme_id");
overseasProgramme = rs.getString("trip.overseasProgrammeName");
tourGuideName = rs.getString("tourguide.name");
tourGuideContact = rs.getString("tourguide.contact");
companyName = rs.getString("agency.companyName");
agentName = rs.getString("agency.agentName");
agentContact = rs.getString("agency.agentContact");
airlineChoice = rs.getString("agency.airlineChoice");
placeOfLodging = rs.getString("accommodation.placeOfLodging");
startDateOfLodging = rs.getString("accommodation.startDate");
endDateOfLodging = rs.getString("accommodation.endDate");
String dbQuery2 = "Select * from tripstaff where trip_id = '" + id + "'";
rs2 = db.readRequest(dbQuery2);
String lec;
ArrayList<String> dbQueryM = new ArrayList<String>();
while (rs2.next()){
lec = rs2.getString("tripstaff.lecturer_id");
dbQueryM.add("Select * from lecturer where id = '" + lec + "'");
}
ArrayList<NypStaff> nsf = new ArrayList<NypStaff>();
for (int i = 0; i < dbQueryM.size(); i++){
rs3 = db.readRequest(dbQueryM.get(i));
if (rs3.next()){
NypStaff temp = new NypStaff();
//set values retrieved from database into attributes
temp.setName(rs3.getString("lecturer.name"));
temp.setEmail(rs3.getString("lecturer.email"));
temp.setContact(rs3.getString("lecturer.contact"));
nsf.add(temp);
}
}
try {
Calendar c = Calendar.getInstance();
Calendar c2 = Calendar.getInstance();
Calendar c3 = Calendar.getInstance();
Calendar c4 = Calendar.getInstance();
Calendar c5 = Calendar.getInstance();
try {
c.setTime(formatter.parse(startDate));
c2.setTime(formatter.parse(endDate));
c3.setTime(formatter.parse(startDateOfLodging));
c4.setTime(formatter.parse(endDateOfLodging));
c5.setTime(formatter.parse(closingDateOfApplication));
}
catch (ParseException e1) {
e1.printStackTrace();
}
c.add(Calendar.DATE, 1);
c2.add(Calendar.DATE, 1);
c3.add(Calendar.DATE, 1);
c4.add(Calendar.DATE, 1);
c5.add(Calendar.DATE, 1);
startDate = formatter.format(c.getTime());
endDate = formatter.format(c2.getTime());
startDateOfLodging = formatter.format(c3.getTime());
endDateOfLodging = formatter.format(c4.getTime());
closingDateOfApplication = formatter.format(c5.getTime());
startDated = formatter.parse(startDate);
endDated = formatter.parse(endDate);
startDatedOfLodging = formatter.parse(startDateOfLodging);
endDatedOfLodging = formatter.parse(endDateOfLodging);
closingDatedOfApplication = formatter.parse(closingDateOfApplication);
c.add(Calendar.DATE, -1);
c2.add(Calendar.DATE, -1);
c3.add(Calendar.DATE, -1);
c4.add(Calendar.DATE, -1);
c5.add(Calendar.DATE, -1);
startDate = formatter.format(c.getTime());
endDate = formatter.format(c2.getTime());
startDateOfLodging = formatter.format(c3.getTime());
endDateOfLodging = formatter.format(c4.getTime());
closingDateOfApplication = formatter.format(c5.getTime());
}
catch (ParseException e1) {
e1.printStackTrace();
}
t.add(new TripSearchy (id, opId, overseasProgramme, name, startDated, startDate, endDated, endDate, costOfTrip, ns, nsf, staffName, tourGuideName, tourGuideContact, companyName, agentName, agentContact, airlineChoice, placeOfLodging, startDatedOfLodging, startDateOfLodging, endDatedOfLodging, endDateOfLodging, maxNoOfParticipants, closingDatedOfApplication, closingDateOfApplication, instructions, psea, fasop, ktpiop));
}
}catch (Exception e) {
e.printStackTrace();
}
db.terminate();
}
It seems that I have exhausted my connection =\ May I know how do I reduce my usage of the connection/increase the capacity of the connection?
Update:
DBController.java
public class DBController {
private DataSource ds;
Connection con;
public void setUp() throws NamingException{
//connect to database
Context ctx = new InitialContext();
ds = (DataSource)ctx.lookup("java:comp/env/jdbc/it2299");
}
public ResultSet readRequest(String dbQuery){
ResultSet rs=null;
try{
con = ds.getConnection();
Statement stmt = con.createStatement();
rs = stmt.executeQuery(dbQuery);
}
catch(Exception e){e.printStackTrace();}
return rs;
}
public int updateRequest(String dbQuery){
int count=0;
try{
con = ds.getConnection();
Statement stmt = con.createStatement();
count=stmt.executeUpdate(dbQuery);
}
catch(Exception e){e.printStackTrace();}
return count;
}
public void terminate(){
try {con.close();}
catch(Exception e){e.printStackTrace();}
}
}
Update 2: This exception occurs when the scope of my ManagedBean(TripTableBean.java) is ViewScoped, it doesn't occur when I change it to SessionScoped. However if it is SessionScoped, I'll need to find a way to kill session and recreate a new session whenever I come to this web page if not my dataTable on this page won't load updated changes from the database.
回答1:
what are you connection pool settings can you post whats in DBController? Tip: db.terminate() should be in finally{} block, may be you are lossing connections on exceptions.
Update: Posting some of the modifications that might help you, but DO CLEAN UP THE CODE for maintenance sake. Look for comments where changes have been made.
public class DBController {
private DataSource ds;
private Connection con;// NEW CHANGE
public void setUp() throws NamingException{
//connect to database
Context ctx = new InitialContext();
ds = (DataSource)ctx.lookup("java:comp/env/jdbc/it2299");
con = ds.getConnection(); // NEW CHANGE
}
public ResultSet readRequest(String dbQuery){
ResultSet rs=null;
try{
//REMOVED CODE FROM HERE
Statement stmt = con.createStatement();
rs = stmt.executeQuery(dbQuery);
}
catch(Exception e){e.printStackTrace();}
return rs;
}
public int updateRequest(String dbQuery){
int count=0;
try{
//REMOVED CODE FROM HERE
Statement stmt = con.createStatement();
count=stmt.executeUpdate(dbQuery);
}
catch(Exception e){e.printStackTrace();}
return count;
}
public void terminate(){
try {con.close();}
catch(Exception e){e.printStackTrace();}
}
}
Code cannot be improved beyond this by me, but I suggest have a look at some of the best practices over net and as suggested by @BalusC. Remember: To close the connection object when done.
回答2:
As you hinted yourself, your code is horrible. You need to ensure that all JDBC resources are acquired and closed in the shortest possibe scope in a try-finally block. Rewrite your code so that it follows the following standard JDBC idiom:
public List<Entity> list() throws SQLException {
Connection connection = null;
PreparedStatement statement = null;
ResultSet resultSet = null;
List<Entity> entities = new ArrayList<Entity>();
try {
connection = Database.getConnection();
statement = connection.prepareStatement("SELECT id, foo, bar FROM entity");
resultSet = statement.executeQuery();
while (resultSet.next()) {
Entity entity = new Entity();
entity.setId(resultSet.getLong("id"));
entity.setFoo(resultSet.getString("foo"));
entity.setBar(resultSet.getString("bar"));
entities.add(entity);
}
} finally {
if (resultSet != null) try { resultSet.close(); } catch (SQLException ignore) {}
if (statement != null) try { statement.close(); } catch (SQLException ignore) {}
if (connection != null) try { connection.close(); } catch (SQLException ignore) {}
}
return entities;
}
See also:
- If I use a singleton class for a database connection, can one user close the connection for everybody?
- JDBC MySql connection pooling practices to avoid exhausted connection pool
来源：https://stackoverflow.com/questions/9045123/org-apache-tomcat-dbcp-dbcp-sqlnestedexception-cannot-get-a-connection-pool-er