如何遍历列表 <T> 并在JSF Facelets中渲染每个项目

Question

I am wondering how to display a List<T> as obtained below in a Facelet:

public List<T> searchByString(String string) {
    return getEntityManager().createNamedQuery("Userdetails.findByUsername").setParameter("username", "%" + string + "%").getResultList();
}

Would a <h:dataTable> be a suitable way?

Answer 1

You're going need to iterate over it. JSF 2 offers three iteration components out the box. Provided that the User entity look like below,

@Entity
public class User {
    private @Id Long id;
    private String username;
    private String email;
    private LocalDate birthdate;
    // Add/generate getters+setters.
}

and that the search results are assigned as a List<User> users property of a bean which is available as #{bean} ,

@Named @RequestScoped
public class Bean {
    private List<User> users;
    // Add/generate postconstruct+getter.
}

here are some examples based on it:

1. <h:dataTable> , an UI component which generates a HTML <table> .

    <h:dataTable value="#{bean.users}" var="user"> <h:column>#{user.id}</h:column> <h:column>#{user.username}</h:column> <h:column><a href="mailto:#{user.email}">#{user.email}</a></h:column> <h:column>#{user.birthdate}</h:column> </h:dataTable> 

2. <ui:repeat> , an UI component which generates no HTML markup (so, you'd have to write all that HTML in the desired fashion yourself, which could easily be changed to eg <ul><li> , or <dl><dt><dd> , or <div><span> , etc):

    <table> <ui:repeat value="#{bean.users}" var="user"> <tr> <td>#{user.id}</td> <td>#{user.username}</td> <td><a href="mailto:#{user.email}">#{user.email}</a></td> <td>#{user.birthdate}</td> </td> </ui:repeat> </table> 

3. <c:forEach> , a tag handler which runs during view build time instead of view render time (background explanation here: JSTL in JSF2 Facelets... makes sense? ), it also doesn't produce any HTML markup:

    <table> <c:forEach items="#{bean.users}" var="user"> <tr> <td>#{user.id}</td> <td>#{user.username}</td> <td><a href="mailto:#{user.email}">#{user.email}</a></td> <td>#{user.birthdate}</td> </td> </c:forEach> </table> 

See also:

• Java EE 6 tutorial - Adding components to a page - using <h:dataTable>
• How and when should I load the model from database for h:dataTable

Answer 2

You can save your List in a class variable, give it a getter and (maybe) a setter. Declare searchByString method as void and call it with let's say a (provided you are using PrimeFaces):

<p:commandLink update="@form" process="@this" action="#{myBean.searchByString}"> 

myBean:

public void searchByString(String string) {     
    userList = getEntityManager().createNamedQuery("Userdetails.findByUsername").setParameter("username", "%" + string + "%").getResultList();
}

provided your table sits in a form that you just updated you could display the List in it.

 <p:dataTable var="user" value="#{myBean.userList}">  
    <p:column headerText="Name">  
        <h:outputText value="#{user.name}" />  
    </p:column>  
 </p:dataTable>