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Calling a Java Method from a JSP File

 原文  2018-09-10 17:29:48  2   1    java/ jsp/ digital/ digital-persona-sdk

Question

Setup: Windows 10 Pro 64 bit, IntelliJ IDEA 2018, JBoss WebServer

I am fairly new to Java and JSP although through research and much reading, I have been able to come up with the following code which implements Digital Persona Libraries to inform the user whether or not a scanner is connected to their computer: 

package com.digitalpersona.sample;

import com.digitalpersona.onetouch.DPFPGlobal;
import com.digitalpersona.onetouch.readers.DPFPReaderDescription;
import com.digitalpersona.onetouch.readers.DPFPReadersCollection;

public class ListReaders {
    public static String readerStatus() {
        String response = "";

        DPFPReadersCollection readers = DPFPGlobal.getReadersFactory().getReaders();
        if (readers == null || readers.size() == 0) {
            response = "There are no readers available.";
        }

        for (DPFPReaderDescription readerDescription : readers)
            response = readerDescription.getSerialNumber();

        return response;
    }
}

The above code works fine when I run it independently on IntelliJ but I am having trouble with calling the readerStatus() method from a JSP file. When I try this: 

<%@ page import="com.digitalpersona.sample.*" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>List Readers</title>
</head>
<body>
<%
    ListReaders deviceStatus = new ListReaders();
    out.println(deviceStatus);
%>
</body>
</html>

I get this: 

com.digitalpersona.sample.ListReaders@133d1476

or 

com.digitalpersona.sample.ListReaders@71f2d51b

or 

com.digitalpersona.sample.ListReaders@1c272943

Basically, the last 8 characters keep changing. And when I try this: 

<%@ page import="com.digitalpersona.sample.*" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>List Readers</title>
</head>
<body>
<%
    ListReaders deviceStatus = new ListReaders();
    String responseMessage = deviceStatus.readerStatus();
    out.println(responseMessage);
%>
</body>
</html>

The result is this: 

Error processing request
Context Path:/HelloWorld_war_exploded
Servlet Path:/listreaders.jsp
Path Info:null
Query String:null
Stack Trace:
javax.servlet.ServletException: java.lang.NoSuchMethodError: com.digitalpersona.sample.ListReaders.readerStatus()Ljava/lang/String;
    at org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:889)
    at org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:818)
    at org.apache.jsp.listreaders_jsp._jspService(listreaders_jsp.java:118)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:433)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:403)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:347)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85)
    at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
    at io.undertow.jsp.JspFileHandler.handleRequest(JspFileHandler.java:32)
    at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
    at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
    at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
    at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
    at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
    at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
    at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
    at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at org.wildfly.extension.undertow.deployment.GlobalRequestControllerHandler.handleRequest(GlobalRequestControllerHandler.java:68)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:292)
    at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:81)
    at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:138)
    at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:135)
    at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
    at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
    at org.wildfly.extension.undertow.security.SecurityContextThreadSetupAction.lambda$create$0(SecurityContextThreadSetupAction.java:105)
    at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
    at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
    at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
    at org.wildfly.extension.undertow.deployment.UndertowDeploymentInfoService$UndertowThreadSetupAction.lambda$create$0(UndertowDeploymentInfoService.java:1508)
    at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:272)
    at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
    at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:104)
    at io.undertow.server.Connectors.executeRootHandler(Connectors.java:326)
    at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:812)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NoSuchMethodError: com.digitalpersona.sample.ListReaders.readerStatus()Ljava/lang/String;
    at org.apache.jsp.listreaders_jsp._jspService(listreaders_jsp.java:101)
    ... 45 more

Can someone please help me get the correct output from: 

return response;

Thanks in advance.

1 answers

solution1
 0  2018-09-10 17:40:09

Forgive me for posting, I have too few XP to comment.

You do not have a user overridden toString() method for the class ListReaders . Thus java will use it's inbuilt methods to display com.digitalpersona.sample.ListReaders@133d1476 

@Override
public String toString() { 
    return "<Your values here>";
}

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