如何手动将Spring MVC视图呈现为html？

java spring spring-mvc

2022-09-01 12:14:38

是否可以在我的控制器映射方法中将我的视图呈现为html，以便我可以将呈现的html作为json对象的一部分返回？

我常用的控制器方法示例：

@RequestMapping(value={"/accounts/{accountId}"}, method=RequestMethod.GET)
public String viewAcc(final HttpServletRequest req, 
        final HttpServletResponse resp, final Model model,
        @PathVariable("accountId") final String docId) {

    // do usual processing ...

    // return only a STRING value, 
    //   which will be used by spring MVC to resolve into myview.jsp or myview.ftl
    //   and populate the model to the template to result in html
    return "myview";
}

我期待的：

@RequestMapping(value={"/accounts/{accountId}"}, method=RequestMethod.GET)
public String viewAcc(final HttpServletRequest req, 
        final HttpServletResponse resp, final Model model,
        @PathVariable("accountId") final String docId) {

    // do usual processing ...

    // manually create the view
    ModelAndView view = ... ? (how)

    // translate the view to the html
    //   and get the rendered html from the view
    String renderedHtml = view.render .. ? (how)

    // create a json containing the html
    String jsonString = "{ 'html' : " + escapeForJson(renderedHtml) + "}"

    try {
        out = response.getWriter();
        out.write(jsonString);
    } catch (IOException e) {
        // handle the exception somehow
    }

    return null;
}

我想知道在控制器方法中创建视图并将视图呈现为html的正确方法是什么。

更新

以下是来自已接受答案指导的工作示例：

View resolvedView = thiz.viewResolver.resolveViewName("myViewName", Locale.US);
MockHttpServletResponse mockResp = new MockHttpServletResponse();
resolvedView.render(model.asMap(), req, mockResp);
System.out.println("rendered html : " + mockResp.getContentAsString());

答案 1

尝试自动连接视图解析器，然后调用以获取视图。resolveViewName("myview", Locale.US)

然后调用视图，向它传递一个“模拟”HTTP 响应，该响应具有用于其输出的 ByteArrayOutputStream，并从 ByteArrayOutputStream 获取 HTML。render()

更新

这是从问题中复制的工作示例。（所以代码实际上是有答案的）

View resolvedView = thiz.viewResolver.resolveViewName("myViewName", Locale.US);
MockHttpServletResponse mockResp = new MockHttpServletResponse();
resolvedView.render(model.asMap(), req, mockResp);
System.out.println("rendered html : " + mockResp.getContentAsString());

答案 2

如果要在与呈现视图相同的区域设置下呈现视图，请尝试处理它的 -method：DispatcherServletrender

/** LocaleResolver used by this servlet */
private LocaleResolver localeResolver;

/** List of ViewResolvers used by this servlet */
private List<ViewResolver> viewResolvers;

/**
 * Render the given ModelAndView.
 * <p>This is the last stage in handling a request. It may involve resolving the view by name.
 * @param mv the ModelAndView to render
 * @param request current HTTP servlet request
 * @param response current HTTP servlet response
 * @throws ServletException if view is missing or cannot be resolved
 * @throws Exception if there's a problem rendering the view
 */
protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
    // Determine locale for request and apply it to the response.
    Locale locale = this.localeResolver.resolveLocale(request);
    response.setLocale(locale);

    View view;
    if (mv.isReference()) {
        // We need to resolve the view name.
        view = resolveViewName(mv.getViewName(), mv.getModelInternal(), locale, request);
        if (view == null) {
            throw new ServletException("Could not resolve view with name '" + mv.getViewName() +
                    "' in servlet with name '" + getServletName() + "'");
        }
    }
    else {
        // No need to lookup: the ModelAndView object contains the actual View object.
        view = mv.getView();
        if (view == null) {
            throw new ServletException("ModelAndView [" + mv + "] neither contains a view name nor a " +
                    "View object in servlet with name '" + getServletName() + "'");
        }
    }

    // Delegate to the View object for rendering.
    if (logger.isDebugEnabled()) {
        logger.debug("Rendering view [" + view + "] in DispatcherServlet with name '" + getServletName() + "'");
    }
    try {
        view.render(mv.getModelInternal(), request, response);
    }
    catch (Exception ex) {
        if (logger.isDebugEnabled()) {
            logger.debug("Error rendering view [" + view + "] in DispatcherServlet with name '" +
                    getServletName() + "'", ex);
        }
        throw ex;
    }
}

/**
 * Resolve the given view name into a View object (to be rendered).
 * <p>The default implementations asks all ViewResolvers of this dispatcher.
 * Can be overridden for custom resolution strategies, potentially based on
 * specific model attributes or request parameters.
 * @param viewName the name of the view to resolve
 * @param model the model to be passed to the view
 * @param locale the current locale
 * @param request current HTTP servlet request
 * @return the View object, or {@code null} if none found
 * @throws Exception if the view cannot be resolved
 * (typically in case of problems creating an actual View object)
 * @see ViewResolver#resolveViewName
 */
protected View resolveViewName(String viewName, Map<String, Object> model, Locale locale,
        HttpServletRequest request) throws Exception {

    for (ViewResolver viewResolver : this.viewResolvers) {
        View view = viewResolver.resolveViewName(viewName, locale);
        if (view != null) {
            return view;
        }
    }
    return null;
}

通常，添加到顶部的字段应该就足够了，但是当自动布线失败时，它也采用回退。@AutowiredDispatcherServlet