第15章 RequestToViewNameTranslator
RequestToViewNameTranslator可以在处理器返回的view为空时使用它根据request获取viewName。Spring MVC提供的实现类只有一个DefaultRequestToViewNameTranslator，这个类也非常简单，只是因为有一些getter/setter方法，所以看起来代码比较多，实际执行解析的只有两个，代码如下：1
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150public 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();
/**
* Set the prefix to prepend to generated view names.
* @param prefix the prefix to prepend to generated view names
*/
public void setPrefix(String prefix) {
this.prefix = (prefix != null ? prefix : "");
}
/**
* Set the suffix to append to generated view names.
* @param suffix the suffix to append to generated view names
*/
public void setSuffix(String suffix) {
this.suffix = (suffix != null ? suffix : "");
}
/**
* Set the value that will replace '{@code /}' as the separator
* in the view name. The default behavior simply leaves '{@code /}'
* as the separator.
*/
public void setSeparator(String separator) {
this.separator = separator;
}
/**
* Set whether or not leading slashes should be stripped from the URI when
* generating the view name. Default is "true".
*/
public void setStripLeadingSlash(boolean stripLeadingSlash) {
this.stripLeadingSlash = stripLeadingSlash;
}
/**
* Set whether or not trailing slashes should be stripped from the URI when
* generating the view name. Default is "true".
*/
public void setStripTrailingSlash(boolean stripTrailingSlash) {
this.stripTrailingSlash = stripTrailingSlash;
}
/**
* Set whether or not file extensions should be stripped from the URI when
* generating the view name. Default is "true".
*/
public void setStripExtension(boolean stripExtension) {
this.stripExtension = stripExtension;
}
/**
* Set if URL lookup should always use the full path within the current servlet
* context. Else, the path within the current servlet mapping is used
* if applicable (i.e. in the case of a ".../*" servlet mapping in web.xml).
* Default is "false".
* @see org.springframework.web.util.UrlPathHelper#setAlwaysUseFullPath
*/
public void setAlwaysUseFullPath(boolean alwaysUseFullPath) {
this.urlPathHelper.setAlwaysUseFullPath(alwaysUseFullPath);
}
/**
* Set if the context path and request URI should be URL-decoded.
* Both are returned <i>undecoded</i> by the Servlet API,
* in contrast to the servlet path.
* <p>Uses either the request encoding or the default encoding according
* to the Servlet spec (ISO-8859-1).
* @see org.springframework.web.util.UrlPathHelper#setUrlDecode
*/
public void setUrlDecode(boolean urlDecode) {
this.urlPathHelper.setUrlDecode(urlDecode);
}
/**
* Set if ";" (semicolon) content should be stripped from the request URI.
* @see org.springframework.web.util.UrlPathHelper#setRemoveSemicolonContent(boolean)
*/
public void setRemoveSemicolonContent(boolean removeSemicolonContent) {
this.urlPathHelper.setRemoveSemicolonContent(removeSemicolonContent);
}
/**
* Set the {@link org.springframework.web.util.UrlPathHelper} to use for
* the resolution of lookup paths.
* <p>Use this to override the default UrlPathHelper with a custom subclass,
* or to share common UrlPathHelper settings across multiple web components.
*/
public void setUrlPathHelper(UrlPathHelper urlPathHelper) {
Assert.notNull(urlPathHelper, "UrlPathHelper must not be null");
this.urlPathHelper = urlPathHelper;
}
/**
* Translates the request URI of the incoming {@link HttpServletRequest}
* into the view name based on the configured parameters.
* @see org.springframework.web.util.UrlPathHelper#getLookupPathForRequest
* @see #transformPath
*/
public String getViewName(HttpServletRequest request) {
String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
return (this.prefix + transformPath(lookupPath) + this.suffix);
}
/**
* Transform the request URI (in the context of the webapp) stripping
* slashes and extensions, and replacing the separator as required.
* @param lookupPath the lookup path for the current request,
* as determined by the UrlPathHelper
* @return the transformed path, with slashes and extensions stripped
* if desired
*/
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;
}
}
getViewName足接口定义的方法，实际解析时就调用它。在getViewName中首先从request获得lookupPath，然后使用transformPath方法对其进行处理后加土前缀后缀返回。transformPath方法的作用简单来说就是根据配置对lookupPath“掐头去尾换分隔符”，它是根据其中的四个属性的设置来处理的，下面分别解释一下这四个属性，其中用到的Slash是一个静态常量，表示”/“。
stripLeadingSlash:如果最前面的字符为Slash是否将其去掉。stripTrailingSlash：如果最后一个字符为Slash是否将其去掉。stripExtension：是否需要去掉扩展名。separator:如果其值与Slash不同则用于替换原来的分隔符Slash。
getViewName中还使用了可以给返回值添加前缀和后缀的prefix和suffix，这些参数都可以配置。可以配置的参数除了这6个外还有4个：urlDecode、removeSemicolonContent、alwaysUseFullPath和urlPathHelper，前三个参数都是用在urlPathHelper中的，urlDecode用于设置url是否需要编解码，一般默认就行；removeSemicolonContent在前面已经说过了．用于设置是否删除url中与分号相关的内容；alwaysUseFullPath用于设置是否总使用完整路径；urlpathHelper是用于处理url的工具，一般使用spring默认提供的就可以了。RequestToViewNameTranslator组件非常简单，本章就介绍到这里。
