java.sql.SQLException: 关闭的连接（读取oracle blob）

读取oracle blob字段时，我读取后set到一个类的属性中，然后再get的时候就得不到了
java.sql.SQLException: 关闭的连接
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112)
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:146)
        at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:208)
        at oracle.sql.BLOB.getDBAccess(BLOB.java:955)
        at oracle.sql.BLOB.getBinaryStream(BLOB.java:229)
        at com.dhcc.servlet.GetImg.doGet(GetImg.java:61)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
        at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:226)
        at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:124)
        at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:283)
        at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:175)
        at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3370)
        at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
        at weblogic.security.service.SecurityManager.runAs(Unknown Source)
        at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2117)
        at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2023)
        at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1359)
        at weblogic.work.ExecuteThread.execute(ExecuteThread.java:200)
        at weblogic.work.ExecuteThread.run(ExecuteThread.java:172)