数据传递--------博客-----------springMVC源码分析--RequestToViewNameTranslator请求到视图名称的转换

参考来源：http://blog.csdn.net/qq924862077/article/details/54286976?utm_source=gold_browser_extension

RequestToViewNameTranslator可以在处理器返回的View为空时使用它根据Request获取viewName。RequestToViewNameTranslator提供的实现类只有一个DefaultRequestToViewNameTranslator。

接口RequestToViewNameTranslator中定义的如下：提供了getViewName抽象方法，其实就是根据request请求获取来组装视图名称。

public interface RequestToViewNameTranslator {

    /**
     * Translate the given {@link HttpServletRequest} into a view name.
     * @param request the incoming {@link HttpServletRequest} providing
     * the context from which a view name is to be resolved
     * @return the view name (or {@code null} if no default found)
     * @throws Exception if view name translation fails
     */
    String getViewName(HttpServletRequest request) throws Exception;

}

其实现类DefaultRequestToViewNameTranslator中的实现如下：其实其简单实现就是将请求名称作为视图名称返回，逻辑还是比较简单的。

@Override
    public String getViewName(HttpServletRequest request) {
        String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
        return (this.prefix + transformPath(lookupPath) + this.suffix);
    }

接下来我们看看RequestToViewNameTranslator在springMVC中的具体运行流程：

首先在DispatcherServlet的doDispatch函数中会设置默认的视图名

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ......
        //设置默认的视图名称
        applyDefaultViewName(processedRequest, mv);
        ......
    }

在applyDefaultViewName中会判断ModelAndView的hasView为空时，就设置viewName

private void applyDefaultViewName(HttpServletRequest request, ModelAndView mv) throws Exception {
        if (mv != null && !mv.hasView()) {
            mv.setViewName(getDefaultViewName(request));
        }
    }

getDefaultViewName的实现逻辑还是在ViewNameTranslator中。

protected String getDefaultViewName(HttpServletRequest request) throws Exception {
        return this.viewNameTranslator.getViewName(request);
    }

在DefaultViewNameTranslator中实现的getViewName的逻辑如下，其实就是将请求路径作为ViewName

@Override
    public String getViewName(HttpServletRequest request) {
        String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
        return (this.prefix + transformPath(lookupPath) + this.suffix);
    }

实现类DefaultViewNameTranslator的完整源码如下：

public class DefaultRequestToViewNameTranslator implements RequestToViewNameTranslator {

    private static final String SLASH = "/";


    private String prefix = "";

    private String suffix = "";

    private String separator = SLASH;

    private boolean stripLeadingSlash = true;

    private boolean stripTrailingSlash = true;

    private boolean stripExtension = true;

    private UrlPathHelper urlPathHelper = new UrlPathHelper();



    public void setPrefix(String prefix) {
        this.prefix = (prefix != null ? prefix : "");
    }

    public void setSuffix(String suffix) {
        this.suffix = (suffix != null ? suffix : "");
    }

    public void setSeparator(String separator) {
        this.separator = separator;
    }

    public void setStripLeadingSlash(boolean stripLeadingSlash) {
        this.stripLeadingSlash = stripLeadingSlash;
    }

    public void setStripTrailingSlash(boolean stripTrailingSlash) {
        this.stripTrailingSlash = stripTrailingSlash;
    }

    public void setStripExtension(boolean stripExtension) {
        this.stripExtension = stripExtension;
    }


    public void setAlwaysUseFullPath(boolean alwaysUseFullPath) {
        this.urlPathHelper.setAlwaysUseFullPath(alwaysUseFullPath);
    }


    public void setUrlDecode(boolean urlDecode) {
        this.urlPathHelper.setUrlDecode(urlDecode);
    }

    public void setRemoveSemicolonContent(boolean removeSemicolonContent) {
        this.urlPathHelper.setRemoveSemicolonContent(removeSemicolonContent);
    }

    public void setUrlPathHelper(UrlPathHelper urlPathHelper) {
        Assert.notNull(urlPathHelper, "UrlPathHelper must not be null");
        this.urlPathHelper = urlPathHelper;
    }

    //根据请求获取视图名称
    @Override
    public String getViewName(HttpServletRequest request) {
        String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
        return (this.prefix + transformPath(lookupPath) + this.suffix);
    }


    protected String transformPath(String lookupPath) {
        String path = lookupPath;
        if (this.stripLeadingSlash && path.startsWith(SLASH)) {
            path = path.substring(1);
        }
        if (this.stripTrailingSlash && path.endsWith(SLASH)) {
            path = path.substring(0, path.length() - 1);
        }
        if (this.stripExtension) {
            path = StringUtils.stripFilenameExtension(path);
        }
        if (!SLASH.equals(this.separator)) {
            path = StringUtils.replace(path, SLASH, this.separator);
        }
        return path;
    }

}