Circular view path [home]: would dispatch back to the current handler URL [/home] again. Check your ViewResolver setup!

Circular view path [home]: would dispatch back to the current handler URL [/home] again. Check your ViewResolver setup! 
(Hint: This may be the result of an unspecified view, due to default view name generation.)

1. 问题的现象

比如在webConfig中定义了一个viewResolver

Circular view path [home]: would dispatch back to the current handler URL [/home] again. Check your ViewResolver setup!

public class WebConfig extends WebMvcConfigurerAdapter {

    //配置JSP视图解析器
    @Bean
    public ViewResolver viewResolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("WEB-INF/views/");
        resolver.setSuffix(".jsp");
        resolver.setExposeContextBeansAsAttributes(true);
        return resolver;
    }
}

然后定义了一个controller，URL路径为"/home", 它返回名字叫home的view

@Controller
public class HomeController {
    @RequestMapping(value = "/home", method=GET)
    public ModelAndView home() {
        String message = "Hello";
        return new ModelAndView("home", "home", message);
    }
}

然后定义了个Test

public class HomeControllerTest {
    @Test
    public void testHomePage() throws Exception {
        HomeController controller = new HomeController();
        MockMvc mockMvc = standaloneSetup(controller).build();
        mockMvc.perform(get("/home")).andExpect(view().name("home"));
    }

}

那么执行Test是就会报类似错误并抛出异常：

Circular view path [home]: would dispatch back to the current handler URL [/home] again. Check your ViewResolver setup! 
(Hint: This may be the result of an unspecified view, due to default view name generation.)

2. 首先，首先说下原因：

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

当没有声明ViewResolver时，spring会给你注册一个默认的ViewResolver，就是JstlView的实例，该对象继承自InternalResoureView。

JstlView用来封装JSP或者同一Web应用中的其他资源，它将model对象作为request请求的属性值暴露出来, 并将该请求通过javax.servlet.RequestDispatcher转发到指定的URL.

Spring认为，这个view的URL是可以用来指定同一web应用中特定资源的，是可以被RequestDispatcher转发的。

也就是说，在页面渲染(render)之前，Spring会试图使用RequestDispatcher来继续转发该请求。如下代码：

if (path.startsWith("/") ? uri.equals(path) : uri.equals(StringUtils.applyRelativePath(uri, path))) {
    throw new ServletException("Circular view path [" + path + "]: would dispatch back " +
                        "to the current handler URL [" + uri + "] again. Check your ViewResolver setup! " +
                        "(Hint: This may be the result of an unspecified view, due to default view name generation.)");
}

从这段代码可以看出，如果你的view name和你的path是相同的字符串，根据Spring的转发规则，就等于让自己转发给自己，会陷入死循环。所以Spring会检查到这种情况，于是抛出Circular view path异常。

3. 其次，如何解决？

通过原因分析，造成问题有两个因素：1). 缺省转发， 2). view和path同名

那么消除这两个因素任何一个就可以解决这个问题。

3.1 解决办法一：消除缺省转发

虽然在controller中已经定义了view, 但在使用Spring Test时却仍然无效，这个不知道什么原因，也许是Spring Test的Bug, 有待探究。既然无效，那就在Test中重新定义一下view

, 这样虽然麻烦点，但毕竟消除了缺省转发，所以可以解决问题。示例代码如下：

public class TestJavaConfig {

    private MockMvc mockMvc;

    @InjectMocks
    private StudentController studentController;

    @Mock
    private StudentService studentService;

    @Before
    public void setUp(){
        MockitoAnnotations.initMocks(this);
        InternalResourceViewResolver resolver = new InternalResourceViewResolver(); //在test中重新配置视图解析器
        resolver.setPrefix("/WEB_INF/views");
        resolver.setSuffix(".jsp");
        mockMvc = MockMvcBuilders.standaloneSetup(studentController).setViewResolvers(resolver).build();

    }
    @Test
    public void testList()throws Exception{
        mockMvc.perform(get("/home")).andExpect(view().name("home"));
    }

3.2 解决办法二：修改view和path，让他们不同名

这个方法最简单，建议用这种办法，比如上面的home视图，只要我们的path不是"/home"就可以，可以改view名字（比如改成homepage），或者修改/path(比如/root).

https://www.cnblogs.com/chry/p/6240965.html

Circular view path [home]: would dispatch back to the current handler URL [/home] again. Check your ViewResolver setup!

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