s2h整合，从数据库读数据通过jsp显示，总是出错！！

时间：2022-09-24 17:30:21
从student表取出数据，HibernateUtil类已经拿到SessionFactory 
	public static List<Student> list() {

		List<Student> students = new ArrayList<Student>();

		String hql = "from Student";


		Session session = HibernateUtil.getSession();

		session.beginTransaction();

		Query query = session.createQuery(hql);

		students = (List<Student>)query.list();

		session.getTransaction().commit();

		return students;

	}



StudentAction代码 
public class StudentAction extends ActionSupport {

	private Student student;

	private List<Student> students;

	private int id;


	public Student getStudent() {

		return student;

	}


	public void setStudent(Student student) {

		this.student = student;

	}


	public List<Student> getStudents() {

		return students;

	}


	public void setStudents(List<Student> students) {

		this.students = students;

	}


	public int getId() {

		return id;

	}


	public void setId(int id) {

		this.id = id;

	}


        public List<Student> list() {

		students = DBStudent.list();

		return students;

	}


	public String add() {

		DBStudent.save(student);

		return SUCCESS;

	}


	public String loadStudent() {

		DBStudent.getStudentById(id);

		return SUCCESS;

	}


	public String update() {

		Student s = DBStudent.getStudentById(id);

		s = student;

		DBStudent.update(s);

		return SUCCESS;

	}


	public String delete() {

		Student s = DBStudent.getStudentById(id);

		DBStudent.delete(s);

		return SUCCESS;

	}


	public String addInput() {

		return INPUT;

	}


	public String updateInput() {

		return INPUT;

	}


struts.xml配置文件 
<?xml version="1.0" encoding="GBK" ?>

<!DOCTYPE struts PUBLIC

	"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"

	"http://struts.apache.org/dtds/struts-2.3.dtd">


<struts>


    <constant name="struts.enable.DynamicMethodInvocation" value="true" />

    <constant name="struts.devMode" value="true" />

	<constant name="struts.i18n.encoding" value="GBK"/>

    <package name="default" namespace="/" extends="struts-default">

        <action name="*_Student" class="com.iman.StudentInfo.action.StudentAction" method="{1}">

            <result>/main.jsp</result>

            <result name="input">/add.jsp</result>

        </action>


    </package>


 


</struts>





jsp页面代码 
<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>

<%@ taglib uri="/struts-tags" prefix="s" %>

<%

request.setCharacterEncoding("GBK");

%>

<%

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

%>


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

  <head>

    <base href="<%=basePath%>">

    

    <title>主页</title>

    

	<meta http-equiv="pragma" content="no-cache">

	<meta http-equiv="cache-control" content="no-cache">

	<meta http-equiv="expires" content="0">    

	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">

	<meta http-equiv="description" content="This is my page">

	<meta http-equiv="Content-Type" content="text/html;charset=GBK">

	<!--

	<link rel="stylesheet" type="text/css" href="styles.css">

	-->


  </head>

  

  <body>

    <h1 align="center">学生信息管理</h1>

    <table align="center" width="70%" height="40px" cellspacing="1" cellpadding="1" border="1">

    	<tr>

    		<th>学号</th>

    		<th>姓名</th>

    		<th>性别</th>

    		<th>年龄</th>

    		<th>班级</th>

    	</tr>

    	<s:iterator value="students" var="student">

    		<tr>

    			<td><s:property value="#student.id"/></td>

    			<td><s:property value="#student.name"/></td>

    			<td><s:property value="#student.sex"/></td>

    			<td><s:property value="#student.age"/></td>

    			<td><s:property value="#student.cnum"/></td>

    		</tr>

    	</s:iterator>

    </table>

    <center>

    <s:form action="list_Student" method="post">

    <s:submit  value="查看所有记录" ></s:submit>

    </s:form>

    </center>

  </body>

</html>





部署运行后，点击“查看所有记录”按钮后出现异常，看信息意思是说类型不匹配，把String类型赋给List了，这是哪里出现的问题啊？？
Struts Problem Report
Struts has detected an unhandled exception: 

Messages: java.util.ArrayList cannot be cast to java.lang.String 
 
File: com/opensymphony/xwork2/DefaultActionInvocation.java 
Line number: 493 


--------------------------------------------------------------------------------

Stacktraces
java.lang.ClassCastException: java.util.ArrayList cannot be cast to java.lang.String 
    com.opensymphony.xwork2.DefaultActionInvocation.saveResult(DefaultActionInvocation.java:493)
    com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:456)
    com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:292)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:255)
    org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
    org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:236)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:236)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:90)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:243)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
    com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept…………………………………………
  

4 个解决方案

#1

[i][/i]

#2

public List<Student> list() { 
        students = DBStudent.list(); 
        return students; 
    } 
list 方法中你返回的值是List类型的数值，而struts中的返回值必须为String类型，所以你这个会报错
你可以吧反法改为
public List<Student> list() { 
        students = DBStudent.list(); 
        return "success"; 
    } 
试试

#3

public String list() { 
        students = DBStudent.list(); 
        return "success"; 
    } 

#4

强制转型 出错了

#1

[i][/i]

#2

public List<Student> list() { 
        students = DBStudent.list(); 
        return students; 
    } 
list 方法中你返回的值是List类型的数值，而struts中的返回值必须为String类型，所以你这个会报错
你可以吧反法改为
public List<Student> list() { 
        students = DBStudent.list(); 
        return "success"; 
    } 
试试

#3

public String list() { 
        students = DBStudent.list(); 
        return "success"; 
    } 

#4

强制转型 出错了
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