将列表传递到 JSP

发布于 2024-12-28 20:32:40 字数 500 浏览 1 评论 0原文

我将 bean 列表传递到 JSP 中，然后我想使用 JSTL 检索一些数据，但没有填充任何内容，只是空标记。有什么想法吗？

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<jsp:useBean id="mailingbean" scope="request" class="com.dmd.jpa.Imp.AmpImp" />
<jsp:useBean id="mb" class="com.dmd.jpa.entity.Amp" /> 
<%
  mb = mailingbean.getResultProdInfo();

 %>
 <data>
 <item>
    <c:out value="<ColourCd> ${mb.apid} </ColourCd>"/>
 </item>
 </data>

原文

I'm passing list of beans into JSP and then I want to use JSTL to retrieve some data but nothing is populated just empty tag.
Any ideas?

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<jsp:useBean id="mailingbean" scope="request" class="com.dmd.jpa.Imp.AmpImp" />
<jsp:useBean id="mb" class="com.dmd.jpa.entity.Amp" /> 
<%
  mb = mailingbean.getResultProdInfo();

 %>
 <data>
 <item>
    <c:out value="<ColourCd> ${mb.apid} </ColourCd>"/>
 </item>
 </data>

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铜锣湾横着走 2025-01-04 20:32:40

Scriptlet 和 EL 不共享相同的变量范围。 EL 将变量解析为 PageContext、HttpServletRequest、HttpSession 和 ServletContext 的属性。 Scriptlet 解析仅在方法或类范围内声明的变量。

在这种特殊情况下，您基本上需要将其设置为请求属性：

<%
  mb = mailingbean.getResultProdInfo();
  request.setAttribute("mb", mb);
%>
<data>
  <item>
    <c:out value="<ColourCd>${mb.apid}</ColourCd>" />
  </item>
</data>

但是，这是没有意义的。以下 JSP bean 声明

<jsp:useBean id="mailingbean" scope="request" class="com.dmd.jpa.Imp.AmpImp" />

将使其可由 ${mailingbean} 使用。因此，您需要做的就是

<data>
  <item>
    <c:out value="<ColourCd>${mailingbean.resultProdInfo.apid}</ColourCd>" />
  </item>
</data>

如果您在 getter 方法中执行数据加载工作，我会将其移至 bean 的构造函数，即此类工作实际所属的地方。

public class AmpImp {

    private List<Amp> resultProdInfo;

    public AmpImp() {
        // Do the business job here.
        resultProdInfo = loadItSomehow();
    }

    public List<Amp> getResultProdInfo() {
        // Do NOT do the business job here. Just return the property.
        return resultProdInfo;
    } 

    // ...
}

另请参阅：

我们的 EL 维基页面

Scriptlets and EL do not share the same variable scope. EL resolves variables as attributes of PageContext, HttpServletRequest, HttpSession and ServletContext. Scriptlets resolves variables which are been declared in the method or class scope only.

In this particular case, you basically need to set it as a request attribute:

<%
  mb = mailingbean.getResultProdInfo();
  request.setAttribute("mb", mb);
%>
<data>
  <item>
    <c:out value="<ColourCd>${mb.apid}</ColourCd>" />
  </item>
</data>

However, this makes no sense. The following JSP bean declaration

<jsp:useBean id="mailingbean" scope="request" class="com.dmd.jpa.Imp.AmpImp" />

will make it available by ${mailingbean} already. So all you need to do is

<data>
  <item>
    <c:out value="<ColourCd>${mailingbean.resultProdInfo.apid}</ColourCd>" />
  </item>
</data>

If you were doing the data loading job in the getter method, I'd move that to the constructor of the bean, there where this kind of job actually belongs.

public class AmpImp {

    private List<Amp> resultProdInfo;

    public AmpImp() {
        // Do the business job here.
        resultProdInfo = loadItSomehow();
    }

    public List<Amp> getResultProdInfo() {
        // Do NOT do the business job here. Just return the property.
        return resultProdInfo;
    } 

    // ...
}