How to loop through a HashMap in JSP

Question

How can I loop through a HashMap in JSP    lt       HashMap lt String  String gt  countries   MainUtils getCountries l     gt    lt select name  country  gt       lt               Here I need to loop through countries        gt   lt  select gt

User · Answer

Below code works for me

first I defined the partnerTypesMap like below in the server side,

Map<String, String> partnerTypes = new HashMap<>();

after adding values to it I added the object to model,

model.addAttribute("partnerTypesMap", partnerTypes);

When rendering the page I use below foreach to print them one by one.

<c:forEach items="${partnerTypesMap}" var="partnerTypesMap">
      <form:option value="${partnerTypesMap['value']}">${partnerTypesMap['key']}</form:option>
</c:forEach>

User · Answer

Depending on what you want to accomplish within the loop  iterate over one of these instead    countries keySet   countries entrySet   countries values

User · Answer

Just the same way as you would do in normal Java code  for  Map Entry lt String  String gt  entry   countries entrySet          String key   entry getKey        String value   entry getValue                   However  scriptlets  raw Java code in JSP files  those  lt     gt  things  are considered a poor practice  I recommend to install JSTL  just drop the JAR file in  WEB-INF lib and declare the needed taglibs in top of JSP   It has a  lt c forEach gt  tag which can iterate over among others Maps  Every iteration will give you a Map Entry back which in turn has getKey   and getValue   methods  Here s a basic example   lt    taglib prefix  quot c quot  uri  quot http   java sun com jsp jstl core quot    gt    lt c forEach items  quot   map  quot  var  quot entry quot  gt      Key     entry key   value     entry value  lt br gt   lt  c forEach gt   Thus your particular issue can be solved as follows   lt    taglib prefix  quot c quot  uri  quot http   java sun com jsp jstl core quot    gt    lt select name  quot country quot  gt       lt c forEach items  quot   countries  quot  var  quot country quot  gt           lt option value  quot   country key  quot  gt   country value  lt  option gt       lt  c forEach gt   lt  select gt   You need a Servlet or a ServletContextListener to place the   countries  in the desired scope  If this list is supposed to be request-based  then use the Servlet s doGet    protected void doGet HttpServletRequest request  HttpServletResponse response        Map lt String  String gt  countries   MainUtils getCountries        request setAttribute  quot countries quot   countries       request getRequestDispatcher  quot  WEB-INF page jsp quot   forward request  response      Or if this list is supposed to be an application-wide constant  then use ServletContextListener s contextInitialized   so that it will be loaded only once and kept in memory  public void contextInitialized ServletContextEvent event        Map lt String  String gt  countries   MainUtils getCountries        event getServletContext   setAttribute  quot countries quot   countries      In both cases the countries will be available in EL by   countries   Hope this helps  See also   Iterate over elements of List and Map using JSTL  lt c forEach gt  tag How to iterate over a nested map in  lt c forEach gt  How to iterate an ArrayList inside a HashMap using JSTL  Using special auto start servlet to initialize on startup and share application data

[java] How to loop through a HashMap in JSP?

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