Home > Java > javaTutorial > How to Iterate Through HashMaps in JSP Using JSTL and Avoid Scriptlets?

How to Iterate Through HashMaps in JSP Using JSTL and Avoid Scriptlets?

Linda Hamilton

Release： 2024-12-17 06:04:26

Original

872 people have browsed it

Looping Through HashMaps in JSP

Traversing a HashMap in JSP is similar to doing so in plain Java code. Utilize the following loop structure:

<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">String key = entry.getKey();
String value = entry.getValue();
// ...

Copy after login

}

Scriptlet Drawbacks

While scriptlets were previously common, they are now regarded as poor practice. Instead, we recommend using JSTL, which provides the tag for iterating over Maps, returning a Map.Entry object with getKey() and getValue() methods in each iteration.

<p><c:forEach items="${map}" var="entry"></p>
<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">Key = ${entry.key}, value = ${entry.value}<br>

Copy after login

JSP Solution

To resolve your specific problem:

<p><select name="country"></p>
<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"><c:forEach items=&quot;${countries}&quot; var=&quot;country&quot;>
    <option value=&quot;${country.key}&quot;>${country.value}</option>
</c:forEach>

Copy after login

To make ${countries} accessible in the requested scope, use a Servlet or ServletContextListener.

Example Use Cases

Here are examples of using Servlet or ServletContextListener:

<pre class="brush:php;toolbar:false">Map<String, String> countries = MainUtils.getCountries();
request.setAttribute(&quot;countries&quot;, countries);
request.getRequestDispatcher(&quot;/WEB-INF/page.jsp&quot;).forward(request, response);</p>
<p>}<br>

Or:

<pre class="brush:php;toolbar:false">Map<String, String> countries = MainUtils.getCountries();
event.getServletContext().setAttribute(&quot;countries&quot;, countries);</p>
<p>}<br>

Further Reading

• Iterating Over Elements of Lists and Maps Using JSTL Tag


• Iterating Over a Nested Map in


• Iterating an ArrayList Inside a HashMap Using JSTL


• Using Special Auto Start Servlet to Initialize on Startup and Share Application Data

The above is the detailed content of How to Iterate Through HashMaps in JSP Using JSTL and Avoid Scriptlets?. For more information, please follow other related articles on the PHP Chinese website!