How do you get the length of a list in the JSF expression language

Question

How would I get the length of an ArrayList using a JSF EL expression      MyBean somelist length    does not work

User · Answer

You can eventually extend the EL language by using the EL Functor  which will allow you to call any Java beans methods  even with parameters

User · Answer

Yes  since some genius in the Java API creation committee decided that  even though certain classes have size   members or length attributes  they won t implement getSize   or getLength   which JSF and most other standards require  you can t do what you want   There s a couple ways to do this   One  add a function to your Bean that returns the length    In class MyBean  public int getSomelistLength     return this somelist length     In your JSF page    MyBean somelistLength    Two  If you re using Facelets  Oh  God  why aren t you using Facelets    you can add the fn namespace and use the length function   In JSF page     fn length MyBean somelist

User · Answer

You can get the length using the following EL     Bean list size

User · Answer

You can eventually extend the EL language by using the EL Functor  which will allow you to call any Java beans methods  even with parameters

User · Answer

Note  This solution is better for older versions of JSTL  For versions greater then 1 1 I recommend using fn length MyBean somelist  as suggested by Bill James   This article has some more detailed information  including another possible solution   The problem is that we are trying to invoke the list s size method  which is a valid LinkedList method   but it s not a JavaBeans-compliant getter method  so the expression list size-1 cannot be evaluated  There are two ways to address this dilemma  First  you can use the RT Core library  like this    lt c rt out value   lt    list list size  -1    gt    gt    Second  if you want to avoid Java code in your JSP pages  you can implement a simple wrapper class that contains a list and provides access to the list s size property with a JavaBeans-compliant getter method  That bean is listed in Listing 2 25   The problem with c rt method is that you need to get the variable from request manually  because it doesn t recognize it otherwise  At this point you are putting in a lot of code for what should be built in functionality  This is a GIANT flaw in the EL  I ended up using the  quot wrapper quot  method  here is the class for it  public class CollectionWrapper        Collection collection       public CollectionWrapper Collection collection            this collection   collection             public Collection getCollection             return collection             public int getSize             return collection size             A third option that no one has mentioned yet is to put your list size into the model  assuming you are using MVC  as a separate attribute  So in your model you would have  quot someList quot  and then  quot someListSize quot   That may be simplest way to solve this issue

User · Answer

You mean size   don t you     MyBean somelist size      works for me  using JBoss Seam which has the Jboss EL extensions

User · Answer

Yes  since some genius in the Java API creation committee decided that  even though certain classes have size   members or length attributes  they won t implement getSize   or getLength   which JSF and most other standards require  you can t do what you want   There s a couple ways to do this   One  add a function to your Bean that returns the length    In class MyBean  public int getSomelistLength     return this somelist length     In your JSF page    MyBean somelistLength    Two  If you re using Facelets  Oh  God  why aren t you using Facelets    you can add the fn namespace and use the length function   In JSF page     fn length MyBean somelist

User · Answer

After 7 years    the facelets solution still works fine for me as a jsf user  include the namespace as  xmlns fn  http   java sun com jsp jstl functions   and use the EL as    fn length myBean someList   for example if using in jsf ui fragment below example works fine   lt ui fragment rendered    fn length myBean someList  gt 0   gt       lt  -- Do something here-- gt   lt  ui fragment gt

User · Answer

You mean size   don t you     MyBean somelist size      works for me  using JBoss Seam which has the Jboss EL extensions

User · Answer

Yes  since some genius in the Java API creation committee decided that  even though certain classes have size   members or length attributes  they won t implement getSize   or getLength   which JSF and most other standards require  you can t do what you want   There s a couple ways to do this   One  add a function to your Bean that returns the length    In class MyBean  public int getSomelistLength     return this somelist length     In your JSF page    MyBean somelistLength    Two  If you re using Facelets  Oh  God  why aren t you using Facelets    you can add the fn namespace and use the length function   In JSF page     fn length MyBean somelist

User · Answer

You can eventually extend the EL language by using the EL Functor  which will allow you to call any Java beans methods  even with parameters

User · Answer

lt    taglib uri  http   java sun com jsp jstl functions  prefix  fn   gt    lt h outputText value  Table Size     fn length SystemBean list     gt    On screen it displays the Table size  Example  Table Size   5

User · Answer

Yes  since some genius in the Java API creation committee decided that  even though certain classes have size   members or length attributes  they won t implement getSize   or getLength   which JSF and most other standards require  you can t do what you want   There s a couple ways to do this   One  add a function to your Bean that returns the length    In class MyBean  public int getSomelistLength     return this somelist length     In your JSF page    MyBean somelistLength    Two  If you re using Facelets  Oh  God  why aren t you using Facelets    you can add the fn namespace and use the length function   In JSF page     fn length MyBean somelist

User · Answer

You can get the length using the following EL     Bean list size

User · Answer

Note  This solution is better for older versions of JSTL  For versions greater then 1 1 I recommend using fn length MyBean somelist  as suggested by Bill James   This article has some more detailed information  including another possible solution   The problem is that we are trying to invoke the list s size method  which is a valid LinkedList method   but it s not a JavaBeans-compliant getter method  so the expression list size-1 cannot be evaluated  There are two ways to address this dilemma  First  you can use the RT Core library  like this    lt c rt out value   lt    list list size  -1    gt    gt    Second  if you want to avoid Java code in your JSP pages  you can implement a simple wrapper class that contains a list and provides access to the list s size property with a JavaBeans-compliant getter method  That bean is listed in Listing 2 25   The problem with c rt method is that you need to get the variable from request manually  because it doesn t recognize it otherwise  At this point you are putting in a lot of code for what should be built in functionality  This is a GIANT flaw in the EL  I ended up using the  quot wrapper quot  method  here is the class for it  public class CollectionWrapper        Collection collection       public CollectionWrapper Collection collection            this collection   collection             public Collection getCollection             return collection             public int getSize             return collection size             A third option that no one has mentioned yet is to put your list size into the model  assuming you are using MVC  as a separate attribute  So in your model you would have  quot someList quot  and then  quot someListSize quot   That may be simplest way to solve this issue

User · Answer

After 7 years    the facelets solution still works fine for me as a jsf user  include the namespace as  xmlns fn  http   java sun com jsp jstl functions   and use the EL as    fn length myBean someList   for example if using in jsf ui fragment below example works fine   lt ui fragment rendered    fn length myBean someList  gt 0   gt       lt  -- Do something here-- gt   lt  ui fragment gt

User · Answer

lt    taglib uri  http   java sun com jsp jstl functions  prefix  fn   gt    lt h outputText value  Table Size     fn length SystemBean list     gt    On screen it displays the Table size  Example  Table Size   5

User · Answer

You mean size   don t you     MyBean somelist size      works for me  using JBoss Seam which has the Jboss EL extensions

User · Answer

You mean size   don t you     MyBean somelist size      works for me  using JBoss Seam which has the Jboss EL extensions

User · Answer

You can eventually extend the EL language by using the EL Functor  which will allow you to call any Java beans methods  even with parameters

[java] How do you get the length of a list in the JSF expression language?

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