问一个数据库连接的问题，请高手解答。。。

Question

为客户做的门户网站，点击顶部的链接时，总出现这种错误，但这种错误没有规律，很难定时发现，
今天上去看了一下，又发现这个问题，我把错误以及源代码贴出来，望高手解答
Error 500--Internal Server Error 
Error code:PRV_RES_015 Error level:warn Error model:null Error description:can't not get Connection of gimp
at com.gever.gimp.info.dao.impl.SortDAODB2Impl.countchildren(SortDAODB2Impl.java:892)
at jsp_servlet._gdca._homepage._gsjj.__gsjj._jspService(__gsjj.java:614)
at weblogic.servlet.jsp.JspBase.service(JspBase.java:33)
at weblogic.servlet.internal.ServletStubImpl$ServletInvocationAction.run(ServletStubImpl.java:996)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:419)
at weblogic.servlet.internal.TailFilter.doFilter(TailFilter.java:28)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:27)
at filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:45)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:27)
at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:316)
at org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1069)
at org.apache.struts.tiles.TilesRequestProcessor.doForward(TilesRequestProcessor.java:274)
at org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:455)
at org.apache.struts.tiles.TilesRequestProcessor.processForwardConfig(TilesRequestProcessor.java:320)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:279)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1435)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:505)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at weblogic.servlet.internal.ServletStubImpl$ServletInvocationAction.run(ServletStubImpl.java:996)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:419)
at weblogic.servlet.internal.TailFilter.doFilter(TailFilter.java:28)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:27)
at filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:45)
at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:27)
at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:6458)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:118)
at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:3661)
at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2630)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:219)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:178)
Caused by: Error code:can't not get Connection of gimp Error level:warn Error model:null Error description:
at com.gever.gimp.util.Utility.getConnection(Utility.java:34)//下面是这个类
at com.gever.gimp.info.dao.impl.SortDAODB2Impl.countchildren//下面有这个类以及相关方法(SortDAODB2Impl.java:873)
... 31 more
 public class Utility {
  private static Utility instance = new Utility();
  private Utility() {
  }
  public static Utility getInstance(){
    return instance;
  }
  public Connection getConnection() throws DAOException{
    Connection cn = null;
    try{
      ConnectionProvider cp = ConnectionProviderFactory.getConnectionProvider(
          "gimp");
      cn = cp.getConnection();
      return cn;
    } catch (Exception e){
      e.printStackTrace();
      throw new DAOException("can't not get Connection of gimp");
    }
  }  public long[] toLongArray(String[] strings){
    long[] result = null;
    if (strings == null){
      return null;
    }
    result = new long[strings.length];
    for(int i=0; i<strings.length; i++){
      result[i] = Long.parseLong(strings[i]);
    }
    return result;
  }  /**
   * 把“2004-10-10”解析为java.sql.Timestamp类型
   * @param date String
   * @return Timestamp
   */
  public static java.sql.Timestamp parseTimestamp(String date){
    return null;
  }  public static boolean isLogon(HttpServletRequest request){
    boolean result = false;
    if (request.getSession().getAttribute(Constant.USER_ID) != null){
      result = true;
    }
    return result;
  }  public static boolean isSuperAdministrator(HttpServletRequest request){
  boolean checkuser=false;
      try{  RoleDAO role=new DefaultRoleDAO();
    Role mrole=new DefaultRole();
    I_User iuer=new DefaultUser();
    String userID =(String)request.getSession().getAttribute(com.gever.gimp.util.Constant.USER_ID);    mrole.setId(1);    iuer.setId(Integer.parseInt(userID));
      if(mrole.getId()==iuer.getId())
        checkuser=true;
      else{
        checkuser=false;
      }    }catch(Exception e){e.printStackTrace();}
    return checkuser;
  }  public static boolean isHasUploadPermisssion(HttpServletRequest request){
    return isHasPermission("GIMP-UPFB", "ALL", request);
  }
  public static boolean isHasDownPermisssion(HttpServletRequest request){
    return isHasPermission("GIMP-DOFB", "ALL", request);
  }  private static boolean isHasPermission(String resourceCode, String operationCode, HttpServletRequest request){
    boolean result = false;
    UserPermission userPermission = null;
    Collection c = (Collection)request.getSession(true).getAttribute(com.gever.sysman.privilege.util.Constants.USER_PERMISSION);
    if (c != null){
      Iterator i = c.iterator();
      while (i.hasNext()){
        userPermission = (UserPermission)i.next();
        if (resourceCode.equals(userPermission.getRes_code()) && operationCode.equals(userPermission.getOpt_code())){
          result = true;
          break;
        }
      }
    }
    return result;
  }
}
//用于计算分类有多少个儿子
    public List countchildren(long fid) throws DAOException {
        Connection connect = null;
        PreparedStatement ps = null;
        PreparedStatement chinum = null;
        List sortlist = new ArrayList();
        int a = 0;
        String sel = "SELECT * FROM GIMP_INFORMATION_SORT WHERE PARENT_ID =" +
            fid +
            " AND STATUS=1 ORDER BY ORDER2";
        try {
            connect = Utility.getInstance().getConnection();
            ps = connect.prepareStatement(sel);
            ResultSet rs = ps.executeQuery();
            while (rs.next()) {
              SortVO show = new SortVO();
                show.setId(rs.getLong("Id"));
                show.setName(rs.getString("Name"));
                show.setDescription(rs.getString("Description"));
                show.setLev(rs.getInt("Lev"));
                show.setStatus(rs.getInt("STATUS"));
                show.setOrder2(rs.getInt("Order2"));
                show.setParentId(rs.getLong("Parent_Id"));
                show.setUrl(rs.getString("Url"));
                show.setIs_home(rs.getInt("Is_home"));
                sortlist.add(show);
            }
            return sortlist; /*返回一个数组*/
        } catch (Exception e1) {
            e1.printStackTrace();
            throw new DAOException("PRV_RES_015", e1);
        } finally {
            super.release(connect, ps);
        }
    }

Answer 1

public List findByPid2(long pid) throws DAOException {       Connection connect = null;
       PreparedStatement ps = null;
       PreparedStatement chinum = null;
       List sortlist = new ArrayList();
       String sel = "SELECT * FROM GIMP_INFORMATION_SORT WHERE PARENT_ID = " +
           pid +
           " AND STATUS=1 ORDER BY ORDER2";
       SearchDAO search = SearchFactory.getInstance().getSearchDAO();
       try {
           connect = Utility.getInstance().getConnection();
           ps = connect.prepareStatement(sel);
           ResultSet rs = ps.executeQuery();
           while (rs.next()) {
               SortVO show = new SortVO();
               List childrenList = countchildren(rs.getLong("Id"));
               show.setId(rs.getLong("Id"));
               show.setName(rs.getString("Name"));
               show.setDescription(rs.getString("Description"));
               show.setLev(rs.getInt("Lev"));
               show.setStatus(rs.getInt("STATUS"));
               show.setOrder2(rs.getInt("Order2"));
               show.setParentId(rs.getLong("Parent_Id"));
               //show.setUrl(rs.getString("Url"));
               show.setIs_home(rs.getInt("Is_home"));
               show.setChildNum(childrenList.size());
               show.setChildren(childrenList);
               show.setInfor(getContent(rs.getLong("Id")));
               if (getContent(rs.getLong("Id")).size() != 0) {
                   //System.out.println("------000001111111111000----------");
                   InformationDAODB2Impl cutIntro = new InformationDAODB2Impl();
                   show.setInfoVo( ( (InformationVO) getContent(rs.getLong(
                       "Id")).get(0)));
    System.out.println("=================job url begin============>>>>");
                   String url = search.setUrlBySortId2(connect,
                       String.valueOf(show.getInfoVo().
                                      getId()), show.getInfoVo().getTitle(),
                       show.getInfoVo().getSortId(), false);
                   System.out.println("=================job  url end============>>>>"+url);
                   show.setUrl(url);
               } else {
                   show.setIntro("");
               }
               sortlist.add(show);
           }
           return sortlist; /*返回一个数组*/
       } catch (Exception e1) {
           e1.printStackTrace();
           throw new DAOException("PRV_RES_015", e1);
       } finally {
           super.release(connect, ps);
       }
   }
//GDCA显示每一个模块分类的前三条子分类名的方法
    public List findByPid(long pid) throws DAOException {        Connection connect = null;
        PreparedStatement ps = null;
        PreparedStatement chinum = null;
        List sortlist = new ArrayList();
        String sel = "SELECT * FROM GIMP_INFORMATION_SORT WHERE PARENT_ID = " +
            pid +
            " AND STATUS=1 ORDER BY ORDER2";
        SearchDAO search = SearchFactory.getInstance().getSearchDAO();
        try {
            connect = Utility.getInstance().getConnection();
            ps = connect.prepareStatement(sel);
            ResultSet rs = ps.executeQuery();
            while (rs.next()) {
                SortVO show = new SortVO();
                List childrenList = countchildren(rs.getLong("Id"));
                show.setId(rs.getLong("Id"));
                show.setName(rs.getString("Name"));
                show.setDescription(rs.getString("Description"));
                show.setLev(rs.getInt("Lev"));
                show.setStatus(rs.getInt("STATUS"));
                show.setOrder2(rs.getInt("Order2"));
                show.setParentId(rs.getLong("Parent_Id"));
                //show.setUrl(rs.getString("Url"));
                show.setIs_home(rs.getInt("Is_home"));
                show.setChildNum(childrenList.size());
                show.setChildren(childrenList);
                show.setInfor(getContent(rs.getLong("Id")));
                if (getContent(rs.getLong("Id")).size() != 0) {
                    //System.out.println("------000001111111111000----------");
                    InformationDAODB2Impl cutIntro = new InformationDAODB2Impl();
                    show.setInfoVo( ( (InformationVO) getContent(rs.getLong(
                        "Id")).get(0)));
                    //System.out.println("------00000222222220000----------");
//                    System.out.println("=============id==============>>>"+String.valueOf(show.getInfoVo().
//                                       getId()));
//                    System.out.println("==========title==============>>>"+show.getInfoVo().getTitle());
//                    System.out.println("=============sortid========>>>>"+show.getInfoVo().getSortId());
                    String url = search.setUrlBySortId(connect,
                        String.valueOf(show.getInfoVo().
                                       getId()), show.getInfoVo().getTitle(),
                        show.getInfoVo().getSortId(), false);
                   // System.out.println("=================url============>>>>"+url);
                    show.setUrl(url);
                } else {
                    show.setIntro("");
                }
                sortlist.add(show);
            }
            return sortlist; /*返回一个数组*/
        } catch (Exception e1) {
            e1.printStackTrace();
            throw new DAOException("PRV_RES_015", e1);
        } finally {
            super.release(connect, ps);
        }
    }

Answer 2

据我参察，返回的connection有问题，请把return cn;写在方法体的最后面。如果发生了异常，你的方法是不会返回任何值的，因为你的异常体没有写返回值代码，在后面调用的时候最好判断一下它是否为null.以下是我稍改后的代码
  public Connection getConnection() throws DAOException{
    Connection cn = null;
    try{
      ConnectionProvider cp = ConnectionProviderFactory.getConnectionProvider(
          "gimp");
      cn = cp.getConnection();
    } catch (Exception e){
      e.printStackTrace();
      throw new DAOException("can't not get Connection of gimp");
    }
    return cn;
  }