How do you reference an constants with EL on a JSP page?
I have an interface Addresses with a constant named URL. I know I can reference it with a scriplet by going: <%=Addresses.URL%>, but how do I do this using EL?
EL 3.0 or newer
If you're already on Java EE 7 / EL 3.0, then the #page import will also import class constants in EL scope.
<%# page import="com.example.YourConstants" %>
This will under the covers be imported via ImportHandler#importClass() and be available as ${YourConstants.FOO}.
Note that all java.lang.* classes are already implicitly imported and available like so ${Boolean.TRUE} and ${Integer.MAX_VALUE}. This only requires a more recent Java EE 7 container server as early versions had bugs in this. E.g. GlassFish 4.0 and Tomcat 8.0.0-1x fails, but GlassFish 4.1+ and Tomcat 8.0.2x+ works. And you need to make absolutely sure that your web.xml is declared conform the latest servlet version supported by the server. Thus with a web.xml which is declared conform Servlet 2.5 or older, none of the Servlet 3.0+ features will work.
Also note that this facility is only available in JSP and not in Facelets. In case of JSF+Facelets, your best bet is using OmniFaces <o:importConstants> as below:
<o:importConstants type="com.example.YourConstants" />
Or adding an EL context listener which calls ImportHandler#importClass() as below:
#ManagedBean(eager=true)
#ApplicationScoped
public class Config {
#PostConstruct
public void init() {
FacesContext.getCurrentInstance().getApplication().addELContextListener(new ELContextListener() {
#Override
public void contextCreated(ELContextEvent event) {
event.getELContext().getImportHandler().importClass("com.example.YourConstants");
}
});
}
}
EL 2.2 or older
This is not possible in EL 2.2 and older. There are several alternatives:
Put them in a Map<String, Object> which you put in the application scope. In EL, map values are accessible the usual Javabean way by ${map.key} or ${map['key.with.dots']}.
Use <un:useConstants> of the Unstandard taglib (maven2 repo here):
<%# taglib uri="http://jakarta.apache.org/taglibs/unstandard-1.0" prefix="un" %>
<un:useConstants className="com.example.YourConstants" var="constants" />
This way they are accessible the usual Javabean way by ${constants.FOO}.
Use Javaranch's CCC <ccc:constantsMap> as desribed somewhere at the bottom of this article.
<%# taglib uri="http://bibeault.org/tld/ccc" prefix="ccc" %>
<ccc:constantsMap className="com.example.YourConstants" var="constants" />
This way they are accessible the usual Javabean way by ${constants.FOO} as well.
If you're using JSF2, then you could use <o:importConstants> of OmniFaces.
<html ... xmlns:o="http://omnifaces.org/ui">
<o:importConstants type="com.example.YourConstants" />
This way they are accessible the usual Javabean way by #{YourConstants.FOO} as well.
Create a wrapper class which returns them through Javabean-style getter methods.
Create a custom EL resolver which first scans the presence of a constant and if absent, then delegate to the default resolver, otherwise returns the constant value instead.
The following does not apply to EL in general, but instead to SpEL (Spring EL) only (tested with 3.2.2.RELEASE on Tomcat 7).
I think it is worth mentioning it here in case someone searches for JSP and EL (but uses JSP with Spring).
<%# taglib prefix="spring" uri="http://www.springframework.org/tags"%>
<spring:eval var="constant" expression="T(com.example.Constants).CONSTANT"/>
You usually place these kinds of constants in a Configuration object (which has getters and setters) in the servlet context, and access them with ${applicationScope.config.url}
You can't. It follows the Java Bean convention. So you must have a getter for it.
I'm defining a constant in my jsp right at the beginning:
<%final String URI = "http://www.example.com/";%>
I include the core taglib in my JSP:
<%#taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
Then, I make the constant available to EL by following statement:
<c:set var="URI" value="<%=URI%>"></c:set>
Now, I can use it later. Here an example, where the value is just written as HTML comment for debugging purposes:
<!-- ${URI} -->
With your constant class, you can just import your class and assign the constants to local variables. I know that my answer is a sort of quick hack, but the question also bumps up when one wants to define constants directly in the JSP.
I implemented like:
public interface Constants{
Integer PAGE_SIZE = 20;
}
-
public class JspConstants extends HashMap<String, String> {
public JspConstants() {
Class c = Constants.class;
Field[] fields = c.getDeclaredFields();
for(Field field : fields) {
int modifier = field.getModifiers();
if(Modifier.isPublic(modifier) && Modifier.isStatic(modifier) && Modifier.isFinal(modifier)) {
try {
Object o = field.get(null);
put(field.getName(), o != null ? o.toString() : null);
} catch(IllegalAccessException ignored) {
}
}
}
}
#Override
public String get(Object key) {
String result = super.get(key);
if(StringUtils.isEmpty(result)) {
throw new IllegalArgumentException("Check key! The key is wrong, no such constant!");
}
return result;
}
}
Next step put instance of this class into servlerContext
public class ApplicationInitializer implements ServletContextListener {
#Override
public void contextInitialized(ServletContextEvent sce) {
sce.getServletContext().setAttribute("Constants", new JspConstants());
}
#Override
public void contextDestroyed(ServletContextEvent sce) {
}
}
add listener to web.xml
<listener>
<listener-class>com.example.ApplicationInitializer</listener-class>
</listener>
access in jsp
${Constants.PAGE_SIZE}
Static properties aren't accessible in EL. The workaround I use is to create a non-static variable which assigns itself to the static value.
public final static String MANAGER_ROLE = 'manager';
public String manager_role = MANAGER_ROLE;
I use lombok to generate the getter and setter so that's pretty well it. Your EL looks like this:
${bean.manager_role}
Full code at https://rogerkeays.com/access-java-static-methods-and-constants-from-el
Yes, you can. You need a custom tag (if you can't find it somewhere else). I've done this:
package something;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Map;
import java.util.TreeMap;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
import org.apache.taglibs.standard.tag.el.core.ExpressionUtil;
/**
* Get all class constants (statics) and place into Map so they can be accessed
* from EL.
* #author Tim.sabin
*/
public class ConstMapTag extends TagSupport {
public static final long serialVersionUID = 0x2ed23c0f306L;
private String path = "";
private String var = "";
public void setPath (String path) throws JspException {
this.path = (String)ExpressionUtil.evalNotNull ("constMap", "path",
path, String.class, this, pageContext);
}
public void setVar (String var) throws JspException {
this.var = (String)ExpressionUtil.evalNotNull ("constMap", "var",
var, String.class, this, pageContext);
}
public int doStartTag () throws JspException {
// Use Reflection to look up the desired field.
try {
Class<?> clazz = null;
try {
clazz = Class.forName (path);
} catch (ClassNotFoundException ex) {
throw new JspException ("Class " + path + " not found.");
}
Field [] flds = clazz.getDeclaredFields ();
// Go through all the fields, and put static ones in a Map.
Map<String, Object> constMap = new TreeMap<String, Object> ();
for (int i = 0; i < flds.length; i++) {
// Check to see if this is public static final. If not, it's not a constant.
int mods = flds [i].getModifiers ();
if (!Modifier.isFinal (mods) || !Modifier.isStatic (mods) ||
!Modifier.isPublic (mods)) {
continue;
}
Object val = null;
try {
val = flds [i].get (null); // null for static fields.
} catch (Exception ex) {
System.out.println ("Problem getting value of " + flds [i].getName ());
continue;
}
// flds [i].get () automatically wraps primitives.
// Place the constant into the Map.
constMap.put (flds [i].getName (), val);
}
// Export the Map as a Page variable.
pageContext.setAttribute (var, constMap);
} catch (Exception ex) {
if (!(ex instanceof JspException)) {
throw new JspException ("Could not process constants from class " + path);
} else {
throw (JspException)ex;
}
}
return SKIP_BODY;
}
}
and the tag is called:
<yourLib:constMap path="path.to.your.constantClass" var="consts" />
All public static final variables will be put into a Map indexed by their Java name, so if
public static final int MY_FIFTEEN = 15;
then the tag will wrap this in an Integer and you can reference it in a JSP:
<c:if test="${consts['MY_FIFTEEN'] eq 15}">
and you don't have to write getters!
You can. Try in follow way
#{T(com.example.Addresses).URL}
Tested on TomCat 7 and java6
Even knowing its a little late, and even knowing this is a little hack - i used the following solution to achieve the desired result. If you are a lover of Java-Naming-Conventions, my advice is to stop reading here...
Having a class like this, defining Constants, grouped by empty classes to create kind of a hierarchy:
public class PERMISSION{
public static class PAGE{
public static final Long SEE = 1L;
public static final Long EDIT = 2L;
public static final Long DELETE = 4L;
...
}
}
can be used from within java as PERMISSION.PAGE.SEE to retrieve the value 1L
To achieve a simliar access-possibility from within EL-Expressions, I did this:
(If there is a coding-god - he hopefully might forgive me :D )
#Named(value="PERMISSION")
public class PERMISSION{
public static class PAGE{
public static final Long SEE = 1L;
public static final Long EDIT = 2L;
public static final Long DELETE = 4L;
...
//EL Wrapper
public Long getSEE(){
return PAGE.SEE;
}
public Long getEDIT(){
return PAGE.EDIT;
}
public Long getDELETE(){
return PAGE.DELETE;
}
}
//EL-Wrapper
public PAGE getPAGE() {
return new PAGE();
}
}
finally, the EL-Expression to access the very same Long becomes: #{PERMISSION.PAGE.SEE} - equality for Java and EL-Access. I know this is out of any convention, but it works perfectly fine.
#Bozho already provided a great answer
You usually place these kinds of constants in a Configuration object (which has getters and setters) in the servlet context, and access them with ${applicationScope.config.url}
However, I feel an example is needed so it brings a bit more clarity and spare someone's time
#Component
public Configuration implements ServletContextAware {
private String addressURL = Addresses.URL;
// Declare other properties if you need as also add corresponding
// getters and setters
public String getAddressURL() {
return addressURL;
}
public void setServletContext(ServletContext servletContext) {
servletContext.setAttribute("config", this);
}
}
There is a workaround that is not exactly what you want, but lets you active almost the same with touching scriptlets in a quite minimal way. You can use scriptlet to put value into a JSTL variable and use clean JSTL code later in the page.
<%# taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%# page import="com.whichever.namespace.Addresses" %>
<c:set var="ourUrl" value="<%=Addresses.URL%>"/>
<c:if test='${"http://www.google.com" eq ourUrl}'>
Google is our URL!
</c:if>
I am trying implement a generic controller class where each method has a structure similar to this:
#RequestMapping(value="cadastra")
#PreAuthorize("hasPermission(#user, 'cadastra_#this.class.name')")
public ModelAndView cadastra() throws InstantiationException, IllegalAccessException {
return new ModelAndView("privado/"+this.entity.getClass().getName()+"/cadastra", "command", this.entity.getClass().newInstance());
}
I am having trouble with the annotation PreAuthorize. the name for the permissionhave this structure: _. right now, I am getting a 403 Error when I try access the view mapped by the method. I also tried other variations like:
#PreAuthorize("hasPermission(#user, 'cadastra_'+#this.class.name)")
or
#PreAuthorize("hasPermission(#user, 'cadastra_#this.getClass().getName()')")
but with the same result. Anyone knows the right way to accomplish this?
UPDATE
I try call this function inside the methods from controller secured by this tag PreAuthorize:
private void expressionParser() {
System.out.println("expressionHandler()");
ExpressionParser parser = new SpelExpressionParser();
Expression expression = parser.parseExpression("'cadastra_'+#this.class.name");
String message = (String) expression.getValue();
System.out.println("Message is " + message);
}
and when I run the application and open the view should be mapped by a method from controller, like this one:
#RequestMapping(value="cadastra")
#PreAuthorize("hasPermission(#user, 'cadastra_'+#this.class.name)")
public ModelAndView cadastra() throws InstantiationException, IllegalAccessException {
this.expressionParser();
return new ModelAndView("privado/"+this.entityClass.getName()+"/cadastra", "command", this.entityClass.newInstance());
}
No message is displayed on the console. So, I am thinking my application somehow aren't calling the methods from my generic controller. Am I right? If so, how I fix this?
My derived controllers follow this structure:
#Controller
#RequestMapping(value="usuario")
public class UsuarioController extends controller<Usuario> {
public UsuarioController() {
super(Usuario.class);
}
}
So you have difficulties with dynamic construction of permission name in the form of [methodName]_[classFullName] in SpEL expression.
See what SpEL documentation says about #this variable below
The variable #this is always defined and refers to the current evaluation object
(against which unqualified references are resolved).
Based on the documentation and a bit digging in the code the actual object the #this represents should be in your case an instance of org.springframework.security.access.expression.method.MethodSecurityExpressionRoot class. The class contains several helpful methods among others also getThis() method that returns the target object on which the secured method (a method annotated with #PreAuthorize) is being invoked.
Armed with this knowledge it should not be a big deal to construct the expression you require. In case of method named "cadastra", it should be as follows.
#PreAuthorize("hasPermission(#user, 'cadastra_'+#this.this.class.name)")
Hopefully it will also work correctly for secured methods inherited from a base class.
So, I solved this issue with this approach:
1) Adding a new method to my generic controller, where I return the name of the class:
public String getName() {
String expressao = entityClass.getName();
String nome_classe = new String();
StringTokenizer st = new StringTokenizer(expressao, ".");
while (st.hasMoreTokens()) {
nome_classe = st.nextToken();
}
return nome_classe;
}
2) Inside the annotation, I use the returned value by this method and concatenate the result with the constant string (using the notation described by the user #pgjecek in this topic):
#PreAuthorize("hasPermission(#user, 'cadastra_'+#this.this.name)")
and now it1s working perfectly.
This question already has answers here:
Localizing enum values in resource bundle
(5 answers)
Closed 7 years ago.
Again something that has been discussed before and where I wanted to share "my" solution and ask for enhancements, other approaches or best practices.
I have several enums where I need internationalization (I need the enum values translated into some languages in order to display them in a jsf page). Examle enum:
public enum TransferStatus {
NOT_TRANSFERRED,
TRANSFERRED
}
Translation would be for example Not yet transferred / Transferred, all good
The translation should be stored in a MessageBundle (properties files). I was searching for an easy, generic solution (best would be without the need of writing extra code in all the enums) that does not need much on the jsf side. Just to mention it, of course it it possible that two different enums shae the same enum value (e.g. values like COMPLETED that have a different meaning in different enums).
The solution I came up with:
(1) Store translations in the properties file like this:
TransferStatus.NOT_TRANSFERRED = Not yet transferred
TransferStatus.TRANSFERRED = Transferred, all good
(2) Make a helper class that takes an enum and generates the lookup key:
public class EnumTranslator {
public static String getMessageKey(Enum<?> e) {
return e.getClass().getSimpleName() + '.' + e.name();
}
}
(3) Add this code to every enum:
public String getKey() {
return EnumTranslator.getMessageKey(this);
}
(4) Now, I can access the translated values of my enums like this:
<h:outputText value="#{enum[order.transferStatus.key]}" />
Which is okay, but what I just don't like is adding the same getKey() method to every enum. There should be something better that that! Now it's your turn, SO :-)
Ok, now this is the complete and ready-to-use solution: (thanks to #Joop Eggen)
Make a class
public final class EnumTranslator {
public static String getMessageKey(Enum<?> e) {
return e.getClass().getSimpleName() + '.' + e.name();
}
}
Make it a custom EL function
<?xml version="1.0" encoding="UTF-8"?>
<facelet-taglib
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facelettaglibrary_2_0.xsd"
version="2.0">
<namespace>http://example.com/enumi18n</namespace>
<function>
<function-name>xlate</function-name>
<function-class>your.package.EnumTranslator</function-class>
<function-signature>String getMessageKey(java.lang.Enum)</function-signature>
</function>
</facelet-taglib>
Add the taglib to your web.xml
<context-param>
<param-name>javax.faces.FACELETS_LIBRARIES</param-name>
<param-value>/WEB-INF/enumi18n.taglib.xml</param-value>
</context-param>
Have properties files enum_en.properties and enum_yourlanguage.properties like this
TransferStatus.NOT_TRANSFERRED = Not transferred
TransferStatus.TRANSFERRED = Transferred
Add the properties files as resource bundles to your faces-config.xml
<resource-bundle>
<base-name>kk.os.obj.jsf.i18n.enum</base-name>
<var>enum</var>
</resource-bundle>
Add the custom taglib to your xhtml files
<html ... xmlns:l="http://example.com/enumi18n">
And - voilà - you can now access the translated enum values in jsf:
<h:outputText value="#{enum[l:xlate(order.transferStatus)]}" />
I would make an EL function, leaving the enum classes as they are:
#{l:xlate(order.transferStatus)}
Okay, xlate has an Object parameter then (or Enum<?>). But the enum classes stay as they are.
The way I'd be doing this takes a bit more code (but far less than the other answers I've seen here), but I feel is more reliable:
#ManagedBean
#ApplicationScoped
public class EnumTranslator {
private <E extends Enum<E>> Map<E, String> getPresentableNames(Class<E> enumClass) {
ResourceBundle resources = ResourceBundle.getBundle(
"com.example.app.MyMessageBundle",
FacesContext.getCurrentInstance().getViewRoot().getLocale());
String prefix = enumClass.getSimpleName() + ".";
Map<E, String> map = new EnumMap<E, String>(enumClass);
for (E value : enumClass.getEnumConstants()) {
map.put(value, resources.getString(prefix + value));
}
return map;
}
// Bean method, accessible via EL
public Map<?, ?> getTransferStatuses() {
return getPresentableNames(TransferStatus.class);
}
}
Then your page can do:
<h:outputText value="#{enumTranslator.transferStatuses[order.transferStatus]}" />
What about:
public interface InternationalizationOfEnum {
default String getKey() {
return EnumTranslator.getMessageKey(this);
}
String name();}
and
public enum anyEnum implements InternationalizationOfEnum{
I want to acces to an attribute inherited by one of my java classes, in a jsp using jstl 1.2 :
Java :
public class LigneDeclarationBean {
private ELigneDeclaration ligneDecla;
private ETypeFormulaire typeForm;
...
public ELigneDeclaration getLigneDecla() {
return ligneDecla;
}
public class ELigneDeclaration extends ZELigneDeclaration implements Serializable {
...
}
public class ZELigneDeclaration implements Serializable {
private String sLibelle;
...
public String getSLibelle() {
return sLibelle;
}
}
JSP :
<%
List<LigneDeclarationBean> listelignes = (List) request.getAttribute("listeLignes");
// Affichage de la liste des ligneDeclas
for (int i = 0; i < listelignes.size(); i++) {
LigneDeclarationBean ligneDecla = listelignes.get(i);
%>
${ligneDecla.ligneDecla.sLibelle}
The error message :
message: The class 'package.ELigneDeclaration ' does
not have the property 'sLibelle'.
However in scriptlet it works fine
<%=ligneDecla.getLigneDecla().getSLibelle()%> return the right value. Is this a limitation of the jstl?
Is there another way to acces to my attribute using this taglib? This project do not use a presentation framework and jstl seems to be the only taglibs I could use.
That might be because of the single letter in the beginning. Try referring to it as ${A.SLibelle}. (i.e. both letters in upper-case).
That's a bit of a special case with EL, because your getter is getSLibelle(), and the parser seems to be unable to understand whether the field is lower or upper-case.
Your problem is found in your getter method:
The correct way to creating a getter method for sLibelle is:
/**
* #return the sLibelle
*/
public String getsLibelle() {
return sLibelle;
}
(yours have a capital S on your getter method declaration name). You can use Bozho's solution or fix the naming of your getter method.
Take the following example.
I have a resource
public class HelloWorldResource extends ServerResource {
#Get
public String represent(String arg) {
return "hello, world (from the cloud!)" + arg;
}
}
That is mapped by
router.attach("/hi/{message}", HelloWorldResource.class);
Is it possible to configure the routing such that accessing /hi/somestuffhere will make restlet fill in the arg parameter in the represent method?
Try this:
String msg = (String) getRequest().getAttributes().get("message");
You can place this in an overriden doInit() method in order to let this happen automatically for all your requests to this resource.