解析模板[]时发生java错误，模板可能不存在，或者任何已配置的模板解析程序都无法访问该模板

Question

下面是我的控制器。如您所见，我想返回html类型

@Controller
public class HtmlController {

  @GetMapping(value = "/", produces = MediaType.TEXT_HTML_VALUE)
  public Employee html() {
    return Employee.builder()
      .name("test")
      .build();
  }
}

我得到了以下错误：

Circular view path [login]: would dispatch back to the current handler URL [/login] again

我通过跟踪this帖子把它搞定了

现在我得到另一个错误：

There was an unexpected error (type=Internal Server Error, status=500).
Error resolving template [], template might not exist or might not be accessible by any of the configured Template Resolvers

有人能帮我为什么我必须依赖ThymalLeaf来提供html内容以及为什么我会遇到这个错误吗

Answer 1

why I have to rely on Thymeleaf for serving HTML content

你不需要。你可以用其他方式来做，你只需要告诉Spring你正在做的事情，也就是说，告诉它返回值是响应本身，而不是用来生成响应的视图的名称

正如Spring documentation所说：

The next table describes the supported controller method return values.

• String: A view name to be resolved with ViewResolver implementations and used together with the implicit model — determined through command objects and @ModelAttribute methods. The handler method can also programmatically enrich the model by declaring a Model argument.

• @ResponseBody: The return value is converted through HttpMessageConverter implementations and written to the response. See @ResponseBody.

• ...

• Any other return value: Any return value that does not match any of the earlier values in this table [...] is treated as a view name (default view name selection through RequestToViewNameTranslator applies).

在您的代码中，Employee对象如何转换为text/html？现在，代码属于“任何其他返回值”类别，但失败了

你可以，例如

• 使用Thymeleaf模板（这是推荐的方法）：

  @GetMapping(path = "/", produces = MediaType.TEXT_HTML_VALUE)
  public String html(Model model) { // <== changed return type, added parameter
      Employee employee = Employee.builder()
          .name("test")
          .build();
      model.addAttribute("employee", employee);
      return "employeedetail"; // view name, aka template base name
  }
  

• 将String toHtml()方法添加到Employee，然后执行以下操作：

  @GetMapping(path = "/", produces = MediaType.TEXT_HTML_VALUE)
  @ResponseBody // <== added annotation
  public String html() { // <== changed return type (HTML is text, i.e. a String)
      return Employee.builder()
          .name("test")
          .build()
          .toHtml(); // <== added call to build HTML content
  }
  

  这实际上使用了一个内置的^{}

• 使用注册的^{}（不推荐）：

  @GetMapping(path = "/", produces = MediaType.TEXT_HTML_VALUE)
  @ResponseBody // <== added annotation
  public Employee html() {
      return Employee.builder()
          .name("test")
          .build();
  }
  

  当然，这需要您编写一个HttpMessageConverter<Employee>实现，它支持text/html，并且register it支持Spring框架