how to compare two strings using if condition inside jsp page?

Question

Jsp code:

<% 
String usermailid=(String)session.getAttribute("Username");
System.out.println("value of session==="+usermailid.equals("null"));
String empty=null;

if(usermailid.equals("null")) {   

%>                          



<% } 

else
{%>


<%}%>

output:

Apr 7, 2014 5:39:31 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
    at org.apache.jsp.election_005fresults_jsp._jspService(election_005fresults_jsp.java:437)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
    at java.lang.Thread.run(Unknown Source)

In the above code i want to compare two strings.but when ever i comapare them i am getting null pointer exception when both the values are null and showing value as false?? so can anyone tell me what is the exact way of comparing two string???

Look here, there is a possible answer http://stackoverflow.com/questions/1900843/is-there-an-easy-way-to-compare-two-strings-in-jsp — ppopoff, Apr 07 '14 at 12:18
First, the Most Important thing is Do not Put Java code inside the JSPs, it is very bad practice. — Stanley Mungai, Apr 07 '14 at 12:55

score 2 · Accepted Answer · answered Apr 07 '14 at 12:17

2

Use simple check

if (usermailid != null)

answered Apr 07 '14 at 12:17

Deepu--Java

3,742
3
19
30

score 2 · Answer 2 · answered Apr 07 '14 at 12:51

2

if(usermailid!=null)

try this it will work.

 String x = null; 
 String x = "null";

both are different

answered Apr 07 '14 at 12:51

tarkikshah

534
6
16

score 1 · Answer 3 · edited May 23 '17 at 11:57

how to compare two strings using if condition inside jsp page?

Answer

Do not write scriptlets <% %> in JSP, because scriptlets shouldn't be used in JSPs for more than a decade. Learn the JSP EL, the JSTL, and use servlet for the Java code. How to avoid Java Code in JSP-Files?

So, I am posting solution using EL syantax.

${!empty Username}

Here Username is directly referred from session scope. empty is operator which checks for null as well as empty.

You can use <c:if> or <c:when> for conditional check.

<c:if test="${!empty Username}">
      //Username is not null here
</c:if>

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score 0 · Answer 4 · answered Apr 07 '14 at 12:19

0

Here you are getting usermailid null and you are trying to compare with String "null". see null is nothing(null) but "null" is a String with null as text.

answered Apr 07 '14 at 12:19

Sanjay Rabari

2,091
1
17
32

score 0 · Answer 5 · answered Apr 07 '14 at 12:19

0

first remove this line:

System.out.println("value of session==="+usermailid.equals("null"));

u may simply write this:

if(null == usermailid) {
  // email id is null
} else {
  // proceed ur logic 
}

answered Apr 07 '14 at 12:19

it is not checking condition and executing only if logic whether the user is inside the session or not inside session.. – User2413 Apr 07 '14 at 12:38

how to compare two strings using if condition inside jsp page?

5 Answers5

Answer

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