Question

Iwas trying to get values from an arraylist (sending this arraylist from a servlet class) and show them on a jsp page. I’m using jstl tags. I looked at some example and I don’t know why but program always gives error. Here is my error message:

org.apache.jasper.JasperException: An exception occurred processing JSP page /result.jsp at line 26

23:    </br></br>Match Score: <c:out value="${score}"/>
24:    <c:forEach items="${alternativedrugs}" var="alternativedrug">
25:    </br></br>
26:    </br></br>Drug <c:out value="${alternativedrug.name}"></c:out>  
27:    </br></br>Drug Description: <c:out value="${alternativedrug.description}"></c:out>  
28:    </br></br>Drug Targets:  <c:out value="${alternativedrug.targets}"></c:out>  
29:    </br></br>Drug Interactions: <c:out value="${alternativedrug.interactions}"></c:out> 

And here is my jstl code:

This Drug Found
<c:forEach items="${alternativedrugs}" var="alternativedrug">
</br></br>Drug Name: <c:out value="${alternativedrug.getName()}"/>
</br></br>Drug Description:     <c:out value="${alternativedrug.getDescription()}"/>
</br></br>Drug Targets:     <c:out value="${alternativedrug.getTargets()}"/>
</br></br>Drug Interactions:    <c:out value="${alternativedrug.getInteractions()}"/>
</br></br>Match Score:  <c:out value="${score}"/>

Object Class:

package drugtargetdisease;

import java.util.ArrayList;


public class MyDrug {

ArrayList<String> partner = new ArrayList();

private String targets = "";
private String name ="";
private String description ="";
private String interactions = "";
public MyDrug(){

}
public String getTargets() {
    return targets;
}
public void setTargets(String targets) {
    this.targets = targets;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public String getDescription() {
    return description;
}
public void setDescription(String description) {
    this.description = description;
}
public String getInteractions() {
    return interactions;
}
public void setInteractions(String interactions) {
    this.interactions = interactions;
}

}

Servlet Part (alternativedrugs is an ArrayList of MyDrug Objects):

otherdrug.setName((String) myentity.getProperty("drug"));
        otherdrug.setDescription(((Text) myentity.getProperty("description")).getValue());
        otherdrug.setInteractions(((Text) myentity.getProperty("interactions")).getValue());
        otherdrug.setTargets(((Text) myentity.getProperty("target")).getValue());
        if(!otherdrug.getName().equals(maindrug.getName())){
        if(MaxScore <= compare.getExpected(maindrug.getTargets(), otherdrug.getTargets(),maindrug.getInteractions(), otherdrug.getInteractions())){
            MaxScore = compare.getExpected(maindrug.getTargets(), otherdrug.getTargets(),maindrug.getInteractions(), otherdrug.getInteractions());
            alternativedrugs.add(otherdrug);
        }
req.setAttribute("alternativedrugs", alternativedrugs);
    req.setAttribute("score", MaxScore);
        try {
            rd.forward(req, resp);
        } catch (ServletException e) {
            e.printStackTrace();
        }    

Full trace:

 Stacktrace:
at org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
at com.google.appengine.tools.development.PrivilegedJspServlet.access$101(PrivilegedJspServlet.java:23)
at com.google.appengine.tools.development.PrivilegedJspServlet$2.run(PrivilegedJspServlet.java:59)
at java.security.AccessController.doPrivileged(Native Method)
at com.google.appengine.tools.development.PrivilegedJspServlet.service(PrivilegedJspServlet.java:57)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.appengine.tools.development.BackendServersFilter.doFilter(BackendServersFilter.java:97)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:94)
at org.mortbay.jetty.servlet.Dispatcher.forward(Dispatcher.java:327)
at org.mortbay.jetty.servlet.Dispatcher.forward(Dispatcher.java:126)
at guestbook.CompareServlet.doPost(CompareServlet.java:85)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166)
at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:110)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:61)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:125)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at com.google.appengine.tools.development.BackendServersFilter.doFilter(BackendServersFilter.java:97)
at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157)
at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388)
at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)
at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:94)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:380)
at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409)
at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: javax.el.PropertyNotFoundException: Could not find property name in class guestbook.MyDrug
at javax.el.BeanELResolver.toBeanProperty(BeanELResolver.java:430)
at javax.el.BeanELResolver.getValue(BeanELResolver.java:290)
at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:231)
at org.apache.el.parser.AstValue.getValue(AstValue.java:123)
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186)
at org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate(PageContextImpl.java:935)
at org.apache.jsp.result_jsp._jspx_meth_c_005fout_005f1(result_jsp.java:201)
at org.apache.jsp.result_jsp._jspx_meth_c_005fforEach_005f0(result_jsp.java:156)
at org.apache.jsp.result_jsp._jspService(result_jsp.java:99)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
... 55 more

Answer 1

So, the error message is Could not find property name in class guestbook.MyDrug.

This means that the is no method

public String getName()

in guestbook.MyDrug. (Note that it could return anything, and not just String. But since the property is name, I assumed it’s of type String).

The JSP EL accesses bean properties. It doesn’t access public fields of your class. Using public fields is a bad practice, and JSP doesn’t encourage that. Make your fields private, and provide accessors (getters and setters) if necessary. If you want to read a field from a JSP, you need a getter.