java - 解析模板 [] 时出错，模板可能不存在，或者任何已配置的模板解析器都无法访问该模板

Question

下面是我的 Controller 。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();
  }
}

我最初遇到以下错误:

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

我按照 this 修复了它发布。

现在我收到另一个错误:

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

有人可以帮助我解决为什么我必须依赖 thymleaf 来提供 html 内容以及为什么我会收到此错误。

Answer 1

why I have to rely on Thymeleaf for serving HTML content

你不知道。你可以用其他方式做到这一点，你只需要告诉 Spring 这就是你正在做的事情，即告诉它返回值是响应本身，而不是用于生成响应的 View 的名称。

作为Spring documentation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 是如何工作的？对象变成 text/html ？现在，代码属于“任何其他返回值”类别，并且失败。

例如，你可以

• 使用 Thymeleaf 模板(这是推荐的方式):

  @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
  }
  

• 添加String toHtml()方法Employee然后执行:

  @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
  }
  

  这实际上使用了内置的 StringHttpMessageConverter .

• 使用已注册的 HttpMessageConverter (不推荐):

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

  这当然需要你写一个 HttpMessageConverter<Employee>支持 text/html 的实现，和register it使用 Spring 框架。