c:when 和 c:if 带有来自 h:dataTable var [重复] 的动态参数
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【中文标题】c:when 和 c:if 带有来自 h:dataTable var [重复] 的动态参数【英文标题】：c:when and c:if with dynamic parameters from h:dataTable var [duplicate] 【发布时间】：2018-03-19 12:16:57 【问题描述】：我对 JSF 和 JAVA 也很陌生，但我正在从事一个大学项目，我遇到了一些无法解决的问题：
基本上我试图显示一个按钮，如果一个人没有被刻录到一个说“inscribir”的课程中，并且有一个动作来刻录它，如果被刻录了相反的动作。
检查是否正在尝试使用 materiaController.cursaMateria(materia.id) 传递 materia 的 id (materia is course) 来检查登录的用户是否已注册该课程。
这是我的代码：
<h:dataTable value="#materiaController.getAll()" var="materia">
<h:column>
<f:facet name="header">id</f:facet>
#materia.id
</h:column>
<h:column>
<f:facet name="header">Nombre</f:facet>
#materia.nombre
</h:column>
<h:column>
<f:facet name="header">Estado</f:facet>
#materia.estado.descripcion
</h:column>
<c:choose>
<c:when test="#materiaController.cursaMateria(materia.id) == false">
<h:column>
<h:form>
<h:commandButton value="Inscribir" action="#materiaController.inscribirMateria(materia.id)"/>
</h:form>
</h:column>
</c:when>
<c:otherwise>
<h:column>
<h:form>
<h:commandButton value="Desinscribir" action="#materiaController.desinscribirMateria(materia.id)"/>
</h:form>
</h:column>
</c:otherwise>
</c:choose>
</h:dataTable>
问题是“cursaMateria”方法总是将参数设为空。顺便说一句，第一列 (id) 打印有相应的 id。
我也尝试了其他方式，但总是一样，无法发送参数：
<c:if test="#materiaController.cursaMateria(materia.id)">
<h:form>
<h:commandButton value="Inscribir" action="#materiaController.inscribirMateria(materia.id)"/>
</h:form>
</c:if>
<c:if test="#!materiaController.cursaMateria(materia.id)">
<h:form>
<h:commandButton value="Desinscribir" action="#materiaController.desinscribirMateria(materia.id)"/>
</h:form>
</c:if>
这样：
<h:panelGroup rendered="#materiaController.cursaMateria(materiaId) == true">
<h:column>
<h:form>
<h:commandButton value="Inscribir" action="#materiaController.inscribirMateria(materiaId)"/>
</h:form>
</h:column>
</h:panelGroup>
<h:panelGroup rendered="#materiaController.cursaMateria(materiaId) == false">
<h:column>
<h:form>
<h:commandButton value="Desinscribir" action="#materiaController.desinscribirMateria(materiaId)"/>
</h:form>
</h:column>
</h:panelGroup>
还有这个：
<h:column>
<h:form>
<h:commandButton value="Inscribir" action="#materiaController.inscribirMateria(materia.id)" rendered="#materiaController.cursaMateria(materia.id)" />
<h:commandButton value="Desinscribir" action="#materiaController.desinscribirMateria(materia.id)" rendered="#!materiaController.cursaMateria(materia.id)"/>
</h:form>
</h:column>
有人可以帮我吗？
先谢谢了。
【问题讨论】：
【参考方案1】：我想这就是您要搜索的内容：要显示已定义的按钮，您可以使用 h:commandButton 的“渲染”参数。结果你应该有这样的东西：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/html" xmlns:ui="http://xmlns.jcp.org/jsf/facelets">
<h:head>
<title>JSF Example</title>
</h:head>
<h:body>
<h:dataTable value="#materiaBean.getAll()" var="materia">
<h:column>
<f:facet name="header">id</f:facet>
#materia.id
</h:column>
<h:column>
<f:facet name="header">Nombre</f:facet>
#materia.nombre
</h:column>
<h:column>
<h:form>
<h:commandButton value="Inscribir" action="#materiaBean.inscribirMateria(materia.id)"
rendered="#not materiaBean.cursaMateria(materia.id)"/>
<h:commandButton value="Desinscribir" action="#materiaBean.desinscribirMateria(materia.id)"
rendered="#materiaBean.cursaMateria(materia.id)"/>
</h:form>
</h:column>
</h:dataTable>
</h:body>
</html>
为了使答案更具说明性，我还创建了托管 bean：
package com.mberazouski.***.components;
import com.mberazouski.***.domain.Materia;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
/**
* Managed bean for supporting operations with <code>materias</code>.
* <p/>
* Bean contains only stub methods with mock logic which have to be replaced with real business logic. It was created as
* a quick example for the answer on
* <a href="https://***.com/questions/46626943/jsf-cwhen-and-cif-with-dynamic-parameters/46630158#46630158">
* ***.com question</a>.
*
* @author mberazouski
*/
@ManagedBean
@ViewScoped
public class MateriaBean implements Serializable
/**
* Stub method for returning collection of @link Materia objects.
* <p/>
* Initially method was implemented in such manner that returns collection of <code>3</code> objects with incremented
* values for <code>id</code> and <code>nombre</code>.
*
* @return collection of three Materia objects
*/
public List<Materia> getAll()
List<Materia> result = new ArrayList<>();
for (int i = 0; i < 3; i++)
Materia materia = new Materia();
materia.setId(i);
materia.setNombre(String.valueOf(i));
result.add(materia);
return result;
/**
* Stub method for action related to controls which are interested in <code>Inscribir</code> action.
* <p/>
* In this realisation just print an id of the @link Materia for which was clicked the button.
*
* @param id id of the @link Materia for which was clicked the button
*/
public void inscribirMateria(int id)
System.out.println("inscribirMateria method called with id: " + id);
/**
* Stub method for action related to controls which are interested in <code>Desinscribir</code> action.
* <p/>
* In this realisation just print an id of the @link Materia for which was clicked the button.
*
* @param id id of the @link Materia for which was clicked the button
*/
public void desinscribirMateria(int id)
System.out.println("desinscribirMateria method called with id: " + id);
/**
* Stub method for determining which button type from two available should be displayed (<code>Desinscribir</code> or
* <code>Inscribir</code>).
* <p/>
* Initially it returns true for each even number.
*
* @param id id of the @link Materia for which was clicked the button
* @return <code>true</code> if id of Materia is even, <code>false</code> otherwise. <code>true</code> is corresponding
* to <code>Desinscribir</code> button and <code>false</code> to <code>Inscribir</code>
*/
public boolean cursaMateria(int id)
if (id % 2 == 0)
return true;
else
return false;
结果页面将如下所示：
希望这能回答您的问题。
【讨论】：
谢谢@MikitaBerazouski 它有效， @LeonardoCabré 欢迎您。祝你好运。以上是关于c:when 和 c:if 带有来自 h:dataTable var [重复] 的动态参数的主要内容，如果未能解决你的问题，请参考以下文章
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