Concatenate strings in JSF/JSP EL and Javascript [duplicate]

Assuming you are using Facelets, here's a relatively good solution:

• create functions.taglib.xml in your WEB-INF

• add a context param indicating the location:

  <context-param>
      <param-name>facelets.LIBRARIES</param-name>
      <param-value>
          /WEB-INF/functions.taglib.xml
      </param-value>
  </context-param>
  

• In the xml put the following:

  <?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE facelet-taglib PUBLIC
    "-//Sun Microsystems, Inc.//DTD Facelet Taglib 1.0//EN"
    "https://facelets.dev.java.net/source/browse/*checkout*/facelets/src/etc/facelet-taglib_1_0.dtd">
  <facelet-taglib xmlns="http://java.sun.com/JSF/Facelet">
      <namespace>http://yournamespace.com/fnc</namespace>
      <function>
          <function-name>concat</function-name>
          <function-class>com.yourpackage.utils.Functions</function-class>
          <function-signature>
              java.lang.String concat(java.lang.String, java.lang.String)
          </function-signature>
      </function>
  </facelet-taglib>
  

• in the page use the following:

  xmlns:fnc="http://yournamespace.com/fnc"
  ....
  oncomplete="#{rich:component(fnc:concat(prefix, '_examinationPanel'))}.show();"
  

• finally, in the Function class define the simple method:

  public static String concat(String string1, String string2) {
     return string1.concat(string2);
  }
  

a simpler solution is to manage the String in the EL like an Object and use the method concat from the class String, something like this:

#{rich:component('constantString'.concat(variable))}.show();