在 JSP 文件中调用 java 方法

Question

我想在我的jsp页面中调用我的方法getSelectedLayouts，方法在哪里

public Iterable<Layouts> getSelectedLayouts(String Subject){
     Session sess=getCurrentSession();
     return sess.createCriteria(Layouts.class, Subject).list();
 }

在类 LayoutManager 中。我使用 Spring Bean 将 LayoutManager 传递到我的 jsp 页面

<custom:useSpringBean var="layoutManager" bean="LayoutManager">

jsp页面要求主题

<form method="post">
      <label for="subjectName">SubjectName:</label>
      <input type="text" name="subjectName" size="50" id="subjectName">
      <input class="button" type="submit" value="Search Layout" name="submit">
</form>

然后我传递给

<jsp:useBean id="subjectName" class="LayoutManager">
    <c:if test="${param.submit!=null}">

           (here's where I want to call my getSelectedLayouts method)

    </c:if>

我一直在尝试使用 scriplets，包括

的变体

<jsp:setProperty name="layout" property="*"/>
((LayoutManager)pageContext.getAttribute("layoutManager")).getSelectedLayout((La‌​youts)pageContext.getAttribute("layout")); 

或者只是

<jsp:setProperty name="layout" property="*"/>
list<Layouts> = LayoutManager.getSelectedLayouts(layout); 

Layouts 是我的对象类

如果我需要提供任何其他信息，请告诉我

编辑：当我尝试时

LayoutManager layoutManager = new LayoutManager();
String subjectNa = request.getParameter("subjectName");
Iterable<Layouts> bla = layoutManager.getSelectedLayouts(subjectNa);

我得到错误列表

org.apache.jasper.JasperException: An exception occurred processing JSP page /search.jsp at line 72

Iterable<Layouts> waters = layoutManager.getSelectedLayouts(subjectNa);

java.lang.NullPointerException
com.amazon.basalt.examples.octane.tomcat.LayoutManager.getCurrentSession(LayoutManager.java:37)
com.amazon.basalt.examples.octane.tomcat.LayoutManager.getSelectedLayouts(LayoutManager.java:50)
org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:502)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:430)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:820)

    root cause

    java.lang.NullPointerException   com.amazon.basalt.examples.octane.tomcat.LayoutManager.getCurrentSession(LayoutManager.java:37)
com.amazon.basalt.examples.octane.tomcat.LayoutManager.getAllLayouts(LayoutManager.java:68)
org.apache.jsp.search_jsp._jspService(search_jsp.java:221)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:388)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:820)

Answer 1

一种可能的解决方案。 （如果使用 scriplets 不是问题。）

<% 
LayoutManager layoutManager = new LayoutManager();
String subjectName = request.getParameter("subjectName");

layoutManager.getSelectedLayouts(subjectName);
%>

记得在 JSP 中导入类

Answer 2

我建议你使用 ajax 来获取布局列表。