如何解决java.lang.IllegalStateException？附Spring MVC相关代码

Let's break down what's causing that java.lang.IllegalStateException in your Spring MVC project and fix it step by step. This exception usually pops up when there's a problem with request mapping, view rendering, model data binding, or bean initialization. Let's go through your code line by line:

1. Missing Request Mapping for memberform() #

Your memberform() method in UserController doesn't have a @RequestMapping annotation. Without this, Spring can't map any HTTP requests to this method, which will cause routing failures and trigger exceptions if your JSP tries to access this functionality.

Fix: Add a @RequestMapping annotation to the method:

@RequestMapping("/Member")
public ModelAndView memberform() {
    List<Membership> members = memberDao.list();
    ModelAndView obj1 = new ModelAndView("User");
    obj1.addObject("member", new Membership());
    obj1.addObject("Members", members);
    return obj1;
}

2. Incorrect Way to Pass Messages on Redirect #

You're using ModelAndView.addObject() to pass messages (Msg1, Msg2) after a redirect. But redirects trigger a new HTTP request, so these attributes won't carry over to the new request. This can cause unexpected behavior and exceptions when your JSP tries to access missing attributes.

Fix: Use RedirectAttributes to add flash attributes (these persist across redirects):

@RequestMapping("/addusr")
public String addusr(@ModelAttribute("user") UserInfo usr, RedirectAttributes redirectAttributes) {
    if(userDao.saveorupdate(usr)) {
        redirectAttributes.addFlashAttribute("Msg1", "User added Successfully");
    } else {
        redirectAttributes.addFlashAttribute("Msg2", "User not added");
    }
    return "redirect:/User";
}

@RequestMapping("/addmember")
public String addmember(@ModelAttribute("member") Membership member, RedirectAttributes redirectAttributes) {
    if(memberDao.saveorupdate(member)) {
        redirectAttributes.addFlashAttribute("Msg1", "Membership User added Successfully");
    } else {
        redirectAttributes.addFlashAttribute("Msg2", "Membership User not added");
    }
    return "redirect:/User";
}

You can then access these messages in your JSP with ${Msg1} or ${Msg2}.

3. Wrong JSTL Tag Library URI #

Your JSP uses an incorrect URI for the JSTL core taglib:

<%@ taglib prefix="c" uri="http://www.springframework.org/tags" %>

This will cause tag parsing failures during JSP rendering, leading to IllegalStateException.

Fix: Replace it with the correct JSTL core URI:

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

4. Form Binding Issues #

A few issues in your JSP form can trigger data binding exceptions that cascade into IllegalStateException:

• Unnecessary name attributes: Spring's <form:input> generates the correct name attribute from the path value—you don't need to add it manually, which can cause conflicts.
• Typos in gender option: "Femal" should be "Female" (this might not directly throw the exception, but it's a data consistency issue).
• Confirm password binding: Ensure your UserInfo class has a Confirmpassword field with proper getter/setter methods. If you don't need to bind this to the model, use a plain HTML <input> instead of <form:input>.

Fix the form code:

<form:form action="${usr}" method="post" commandName="user">
    <form:input type="text" path="First_name" placeholder="First Name"/>
    <form:input type="text" path="Last_name" placeholder="Last Name"/>
    <form:input type="text" path="Email" placeholder="Email"/>
    <form:input type="text" path="Location" placeholder="Location"/>
    <form:input type="password" path="password" placeholder="Password"/>
    <form:input type="password" path="Confirmpassword" placeholder="Confirm Password"/>
    <p><font face="'Merienda', cursive" align="left">Gender</font></p>
    <div style="font-weight: normal;font-style:'Open Sans', sans-serif; font-size:17px">
        <form:radiobutton path="gender" value="Male"/>Male
        <form:radiobutton path="gender" value="female"/>Female
    </div>
    <!-- Don't forget to add a submit button! Your form is missing one -->
    <button type="submit">Sign Up</button>
</form:form>

Note: I added a submit button since your original form didn't have one—without it, users can't submit the form.

5. Incorrect @Autowired for Entity Classes #

You're autowiring UserInfo and Membership entities directly in your controller:

@Autowired UserInfo userInfo;
@Autowired Membership membership;

Entities are usually plain POJOs, not Spring-managed beans (unless you explicitly configure them as such). Autowiring them will fail during controller initialization, leading to IllegalStateException.

Fix: Remove these autowires and instantiate the objects directly where needed:

// Remove these lines:
// @Autowired UserInfo userInfo;
// @Autowired Membership membership;

// In userform():
obj.addObject("user", new UserInfo());

// In memberform():
obj1.addObject("member", new Membership());

Final Checks #

• Verify your view resolver is configured correctly (ensure User.jsp is in the right location, e.g., WEB-INF/views/ if you're using InternalResourceViewResolver).
• Check the full stack trace of the IllegalStateException to pinpoint the exact cause (e.g., if it's a view not found error or a bean initialization failure).

内容的提问来源于stack exchange，提问作者indu ECE