This is meant to be an extensive canonical question & answer post for these types of questions.
I'm trying to write a Spring MVC web application where users can add movie names to an in-memory collection. It's configured like so
public class Application extends AbstractAnnotationConfigDispatcherServletInitializer {
protected Class<?>[] getRootConfigClasses() {
return new Class<?>[] {};
}
protected Class<?>[] getServletConfigClasses() {
return new Class<?>[] { SpringServletConfig.class };
}
protected String[] getServletMappings() {
return new String[] { "/" };
}
}
and
@Configuration
@ComponentScan("com.example")
public class SpringServletConfig extends WebMvcConfigurationSupport {
@Bean
public InternalResourceViewResolver resolver() {
InternalResourceViewResolver vr = new InternalResourceViewResolver();
vr.setPrefix("WEB-INF/jsps/");
vr.setSuffix(".jsp");
return vr;
}
}
There's a single @Controller
class in the com.example
package
@Controller
public class MovieController {
private final CopyOnWriteArrayList<Movie> movies = new CopyOnWriteArrayList<>();
@RequestMapping(path = "/movies", method = RequestMethod.GET)
public String homePage(Model model) {
model.addAttribute("movies", movies);
return "index";
}
@RequestMapping(path = "/movies", method = RequestMethod.POST)
public String upload(@ModelAttribute("movie") Movie movie, BindingResult errors) {
if (!errors.hasErrors()) {
movies.add(movie);
}
return "redirect:/movies";
}
public static class Movie {
private String filmName;
public String getFilmName() {
return filmName;
}
public void setFilmName(String filmName) {
this.filmName = filmName;
}
}
}
WEB-INF/jsps/index.jsp
contains
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Movies</title>
</head>
<body>
Current Movies:
<c:forEach items="${movies}" var="movieItem">
<ul>
<li>${movieItem.filmName}</li>
</ul>
</c:forEach>
<form:form>
<div>Movie name:</div>
<form:input path="filmName" type="text" id="name" />
<input type="submit" value="Upload">
</form:form>
</body>
</html>
The application is configured with context path /Example
. When I send a GET request to
http://localhost:8080/Example/movies
the request fails, Spring MVC responds with a 500 status code, and reports the following exception and stack trace
java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'command' available as request attribute
org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:144)
org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getBindStatus(AbstractDataBoundFormElementTag.java:168)
org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getPropertyPath(AbstractDataBoundFormElementTag.java:188)
org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.getName(AbstractDataBoundFormElementTag.java:154)
org.springframework.web.servlet.tags.form.AbstractDataBoundFormElementTag.writeDefaultAttributes(AbstractDataBoundFormElementTag.java:117)
org.springframework.web.servlet.tags.form.AbstractHtmlElementTag.writeDefaultAttributes(AbstractHtmlElementTag.java:422)
org.springframework.web.servlet.tags.form.InputTag.writeTagContent(InputTag.java:142)
org.springframework.web.servlet.tags.form.AbstractFormTag.doStartTagInternal(AbstractFormTag.java:84)
org.springframework.web.servlet.tags.RequestContextAwareTag.doStartTag(RequestContextAwareTag.java:80)
org.apache.jsp.WEB_002dINF.jsps.index_jsp._jspx_meth_form_005finput_005f0(index_jsp.java:267)
org.apache.jsp.WEB_002dINF.jsps.index_jsp._jspx_meth_form_005fform_005f0(index_jsp.java:227)
org.apache.jsp.WEB_002dINF.jsps.index_jsp._jspService(index_jsp.java:142)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168)
org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1257)
org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1037)
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:980)
org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
I expected the JSP to generate an HTML <form>
with a single text input, for a Movie
name, and a submit button, that I can use to send a POST request with a new Movie
. Why does the JSP servlet instead fail to render Spring's <form:form>
tag?
You're trying to use Spring MVC's form tag.
This tag renders an HTML
form
tag and exposes a binding path to inner tags for binding. It puts the command object in thePageContext
so that the command object can be accessed by inner tags. [..]Let’s assume we have a domain object called
User
. It is a JavaBean with properties such asfirstName
andlastName
. We will use it as the form backing object of our form controller which returnsform.jsp
.
In other words, Spring MVC will extract a command object and use its type as a blueprint for binding path
expressions for form
's inner tags, like input
or checkbox
, to render an HTML form
element.
This command object is also called a model attribute and its name is specified in the form
tag's modelAttribute
or commandName
attributes. You've omitted it in your JSP
<form:form>
You could've specified a name explicitly. Both of these are equivalent.
<form:form modelAttribute="some-example-name">
<form:form commandName="some-example-name">
NOTE: Spring 5 has removed the commandName
attribute, see the upgrade notes, here.
The default attribute name is command
(what you see in error message). A model attribute is an object, typically a POJO or collection of POJOs, that your application supplies to the Spring MVC stack and which the Spring MVC stack exposes to your view (ie. the M to the V in MVC).
Spring MVC collects all model attributes in a ModelMap
(they all have names) and, in the case of JSPs, transfers them to the HttpServletRequest
attributes, where JSP tags and EL expressions have access to them.
In your example, your @Controller
handler method which handles a GET
to the path /movies
adds a single model attribute
model.addAttribute("movies", movies); // not named 'command'
and then forwards to the index.jsp
. This JSP then tries to render
<form:form>
...
<form:input path="name" type="text" id="name" />
...
</form:form>
While rendering this, FormTag
(in reality, the InputTag
) tries to find a model attribute named command
(the default attribute name) so that it can produce an HTML <input>
element with a name
attribute constructed from the path
expression and the corresponding property value, ie. the result of Movie#getFilmName()
.
Since it cannot find it, it throws the exception you see
java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'command' available as request attribute
The JSP engine catches it and responds with a 500 status code. If you want to take advantage of a Movie
POJO to simply construct your form correctly, you can add a model attribute explicitly with
model.addAttribute("movie", new Movie());
or have Spring MVC create and add one for you (must have an accessible parameterless constructor)
@RequestMapping(path = "/movies", method = RequestMethod.GET)
public String homePage(@ModelAttribute("command") Movie movie, Model model) {...}
Alternatively, include a @ModelAttribute
annotated method in your @Controller
class
@ModelAttribute("command")
public Movie defaultInstance() {
Movie movie = new Movie();
movie.setFilmName("Rocky II");
return movie;
}
Note that Spring MVC will call this method and implicitly add the object returned to its model attributes for each request handled by the enclosing @Controller
.
You may have guessed from this description that Spring's form
tag is more suited for rendering an HTML <form>
from an existing object, with actual values. If you want to simply create a blank <form>
, it may be more appropriate to construct it yourself and not rely on any model attributes.
<form method="post" action="${pageContext.request.contextPath}/movies">
<input name="filmName" type="text" />
<input type="submit" value="Upload" />
</form>
On the receiving side, your POST
handler method, will still be able to extract the filmName
input value and use it to initialize a Movie
object.
As we've seen, FormTag
looks for a model attribute named command
by default or with the name specified in either modelAttribute
or commandName
. Make sure you're using the right name.
ModelMap
has a addAttribute(Object)
method which adds
the supplied attribute to this
Map
using a generated name.
where the general convention is to
return the uncapitalized short name of the [attribute's]
Class
, according to JavaBeans property naming rules: So,com.myapp.Product
becomesproduct
;com.myapp.MyProduct
becomesmyProduct
;com.myapp.UKProduct
becomesUKProduct
If you're using this (or a similar) method or if you're using one of the @RequestMapping
supported return types that represents a model attribute, make sure the generated name is what you expect.
Another common error is to bypass your @Controller
method altogether. A typical Spring MVC application follows this pattern:
DispatcherServlet
selects @RequestMapping
method to handle requestDispatcherServlet
adds model attributes to HttpServletRequest
and forwards request to JSP corresponding to view nameIf, by some misconfiguration, you skip the @RequestMapping
method altogether, the attributes will not have been added. This can happen
WEB-INF
, orwelcome-list
of your web.xml
contains your JSP resource, the Servlet container will render it directly, bypassing the Spring MVC stack entirelyOne way or another, you want your @Controller
to be invoked so that the model attributes are added appropriately.
BindingResult
have to do with this?A BindingResult
is a container for initialization or validation of model attributes. The Spring MVC documentation states
The
Errors
orBindingResult
parameters have to follow the model object that is being bound immediately as the method signature might have more than one model object and Spring will create a separateBindingResult
instance for each of them [...]
In other words, if you want to use BindingResult
, it has to follow the corresponding model attribute parameter in a @RequestMapping
method
@RequestMapping(path = "/movies", method = RequestMethod.POST)
public String upload(@ModelAttribute("movie") Movie movie, BindingResult errors) {
BindingResult
objects are also considered model attributes. Spring MVC uses a simple naming convention to manage them, making it easy to find a corresponding regular model attribute. Since the BindingResult
contains more data about the model attribute (eg. validation errors), the FormTag
attempts to bind to it first. However, since they go hand in hand, it's unlikely one will exist without the other.
I tried to migrate my application to Spring5 and noticed the same issue. It was caused by the moment that the 'commandName' attribute is not supported anymore and I had to use 'modelAttribute' instead.
I had this error on a screen with multiple forms that do a search. Each form posts to its own controller method with results shown on same screen.
Problem: I missed adding the other two forms as model attributes in each controller method causing that error when screen renders with results.
Form1 -> bound to Bean1 (bean1) -> Posting to /action1
Form2 -> bound to Bean2 (bean2) -> Posting to /action2
Form3 -> bound to Bean3 (bean2) -> Posting to /action3
@PostMapping
public String blah(@ModelAttribute("bean1") Bean1 bean, Model model){
// do something with bean object
// do not miss adding other 2 beans as model attributes like below.
model.addAttribute("bean2", new Bean2());
model.addAttribute("bean3", new Bean3());
return "screen";
}
@PostMapping
public String blahBlah(@ModelAttribute("bean2") Bean2 bean, Model model){
// do something with bean object
// do not miss adding other 2 beans as model attributes like below.
model.addAttribute("bean1", new Bean1());
model.addAttribute("bean3", new Bean3());
return "screen";
}
@PostMapping
public String blahBlahBlah(@ModelAttribute("bean3") Bean3 bean, Model model){
// do something with bean object
// do not miss adding other 2 beans as model attributes like below.
model.addAttribute("bean1", new Bean1());
model.addAttribute("bean2", new Bean2());
return "screen";
}
To make things simple with the form tag just add a "commandName" which is a horrible name for what it is actually looking for...it wants the object you named in the MdelAttribute annotation. So in this case commandName="movie".
That'll save you reading long winded explanations friend.
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