我有一个bean将结果保存在控制器中，我将它传递给jsp jstl标签。我需要使用JSTL迭代它并呈现结果。我从两个不同的表，用户和地址获取列表。然后迭代它给我正确的输出，但是当我使用JSTL访问同一个对象时它会抛出异常。如果我需要添加任何其他内容，请查看并告诉我。
DAO班级：
String queryString_user = "from User u where u.username = :username";
Query query = session.createQuery(queryString_user).setParameter("username", user);
List<User> userDetails= query.list();
bean从两个表中获取数据
User.java
package com.application.walker.service;
import javax.persistence.Entity;
/**
* User generated by hbm2java
*/
@Entity
public class User implements java.io.Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
private Integer id;
private Address address;
private String firstName;
private String lastName;
private String username;
private String dob;
private String emailAddress;
private Creditcard creditcard;
public User() {
}
public User(Address address, String username, String emailAddress) {
this.address = address;
this.username = username;
this.emailAddress = emailAddress;
}
public User(Address address, String firstName, String lastName,
String username, String dob, String emailAddress,
Creditcard creditcard) {
this.address = address;
this.firstName = firstName;
this.lastName = lastName;
this.username = username;
this.dob = dob;
this.emailAddress = emailAddress;
this.creditcard = creditcard;
}
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
public Address getAddress() {
return this.address;
}
public void setAddress(Address address) {
this.address = address;
}
public String getFirstName() {
return this.firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return this.lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getUsername() {
return this.username;
}
public void setUsername(String username) {
this.username = username;
}
public String getDob() {
return this.dob;
}
public void setDob(String dob) {
this.dob = dob;
}
public String getEmailAddress() {
return this.emailAddress;
}
public void setEmailAddress(String emailAddress) {
this.emailAddress = emailAddress;
}
public Creditcard getCreditcard() {
return this.creditcard;
}
public void setCreditcard(Creditcard creditcard) {
this.creditcard = creditcard;
}
}
Address.Java
package com.application.walker.service;
import java.util.HashSet;
import java.util.Set;
/**
* Address generated by hbm2java
*/
public class Address implements java.io.Serializable {
/**
*
*/
private static final long serialVersionUID = 1L;
private Integer id;
private String addressLine1;
private String addressLine2;
private String addressLine3;
private String city;
private String state;
private Integer zipcode;
private Set users = new HashSet(0);
public Address() {
}
public Address(String addressLine1, String addressLine2,
String addressLine3, String city, String state, Integer zipcode,
Set users) {
this.addressLine1 = addressLine1;
this.addressLine2 = addressLine2;
this.addressLine3 = addressLine3;
this.city = city;
this.state = state;
this.zipcode = zipcode;
this.users = users;
}
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
public String getAddressLine1() {
return this.addressLine1;
}
public void setAddressLine1(String addressLine1) {
this.addressLine1 = addressLine1;
}
public String getAddressLine2() {
return this.addressLine2;
}
public void setAddressLine2(String addressLine2) {
this.addressLine2 = addressLine2;
}
public String getAddressLine3() {
return this.addressLine3;
}
public void setAddressLine3(String addressLine3) {
this.addressLine3 = addressLine3;
}
public String getCity() {
return this.city;
}
public void setCity(String city) {
this.city = city;
}
public String getState() {
return this.state;
}
public void setState(String state) {
this.state = state;
}
public Integer getZipcode() {
return this.zipcode;
}
public void setZipcode(Integer zipcode) {
this.zipcode = zipcode;
}
public Set getUsers() {
return this.users;
}
public void setUsers(Set users) {
this.users = users;
}
}
Spring Controller类
@RequestMapping(value= "/userinformation",params = "userinfo",method=RequestMethod.POST)
private ModelAndView retrieveInformation(@RequestParam String username, HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException{
User user = new User();
ModelAndView model = new ModelAndView();
getWalkerDaoOperations().updateUser(user);
List user_records =getWalkerService().retireveUserbyUserName(username);
if(!(user_records.isEmpty())){
model.addObject("user_records", user_records);
model.setViewName("userinformation");
request.setAttribute("user_records", user_records);
RequestDispatcher requestDispatcher = request.getRequestDispatcher("userinformation.jsp");
requestDispatcher.forward(request, response);
//System.out.println(requestDispatcher);
}else{
String message = "user does not exists";
model.addObject("message", message);
model.setViewName("searchuser");
}
return model;
}
JSP：
<c:forEach var="user_records" items="${user_records}">
<tr>
<td><c:out value="${user_records.firstName}"></c:out></td>
<td><c:out value="${user_records.lastName}"></c:out></td>
<td><c:out value="${user_records.username}"></c:out></td>
<td><c:out value="${user_records.emailAddress}"></c:out></td>
<td><c:out value="${user_records.dob}"></c:out></td>
<c:forEach var="user_records_address" items="${user_records.address}">
<td><c:out value="${user_records_address.addressLine1}"></c:out></td>
<%-- <td><c:out value="${user_records_address.addressLine2}"></c:out></td>
<td><c:out value="${user_records_address.addressLine3}"></c:out></td>
<td><c:out value="${user_records_address.city}"></c:out></td>
<td><c:out value="${user_records_address.state}"></c:out></td> --%>
</c:forEach>
</tr>
</c:forEach>
但它引发了以下异常：有些人可以告诉我需要做出哪些改变。从过去2天开始，我就被困在这里了。提前致谢
SEVERE: Servlet.service() for servlet [walker] in context with path [/walker] threw exception [An exception occurred processing JSP page /userinformation.jsp at line 40
37: <td><c:out value="${user_records.dob}"></c:out></td>
38:
39:
40: <c:forEach var="user_records_address" items="${user_records.address}">
41: <td><c:out value="${user_records_address.addressLine1}"></c:out></td>
42: <%-- <td><c:out value="${user_records_address.addressLine2}"></c:out></td>
43: <td><c:out value="${user_records_address.addressLine3}"></c:out></td>
Stacktrace:] with root cause
javax.servlet.jsp.JspTagException: Don't know how to iterate over supplied "items" in <forEach>
at org.apache.taglibs.standard.tag.common.core.ForEachSupport.toForEachIterator(ForEachSupport.java:274)
at org.apache.taglibs.standard.tag.common.core.ForEachSupport.supportedTypeForEachIterator(ForEachSupport.java:238)
at org.apache.taglibs.standard.tag.common.core.ForEachSupport.prepare(ForEachSupport.java:155)
at javax.servlet.jsp.jstl.core.LoopTagSupport.doStartTag(LoopTagSupport.java:256)
at org.apache.jsp.userinformation_jsp._jspx_meth_c_005fforEach_005f1(userinformation_jsp.java:345)
at org.apache.jsp.userinformation_jsp._jspx_meth_c_005fforEach_005f0(userinformation_jsp.java:209)
at org.apache.jsp.userinformation_jsp._jspx_meth_form_005fform_005f0(userinformation_jsp.java:140)
at org.apache.jsp.userinformation_jsp._jspService(userinformation_jsp.java:87)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:749)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:487)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:412)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:339)
at com.application.walker.controller.LoginController.retrieveInformation(LoginController.java:84)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:176)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:426)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:414)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
at java.lang.Thread.run(Thread.java:695)
答案 0 :(得分：1)
Address不是Iterable，因此无法用作forEach标记中的Collection。你可以做到
<c:forEach var="user_record" items="${user_records}">
<td>${user_record.firstName}></td>
<td>${user_record.lastName}></td>
<td>${user_record.address.addressLine1}></td>
<td>${user_record.address.addressLine2}></td>
<td>${user_record.address.addressLine3}></td>
...
</c:forEach>