擴展Sitemesh3 DecoratorSelector實現基於請求參數調用裝飾模板頁面的實現

//擴展入口Filter實現：
package lab.s2jh.core.web.sitemesh;
 
import org.sitemesh.DecoratorSelector;
import org.sitemesh.builder.SiteMeshFilterBuilder;
import org.sitemesh.config.ConfigurableSiteMeshFilter;
import org.sitemesh.webapp.WebAppContext;
 
/**
 * 擴展實現注入基於request參數decorator值進行動態定位裝飾器的選擇器
 */
public class ParamConfigurableSiteMeshFilter extends ConfigurableSiteMeshFilter {
 
    protected void applyCustomConfiguration(SiteMeshFilterBuilder builder) {
        //獲取原有默認配置裝飾選擇器
        DecoratorSelector<WebAppContext> defaultDecoratorSelector = builder.getDecoratorSelector();
        //賦給自定義裝飾選擇器，則自定義規則未匹配時調用默認選擇器獲取
        builder.setCustomDecoratorSelector(new ParamDecoratorSelector(defaultDecoratorSelector));
    }
}

//定製裝飾選擇器實現：
package lab.s2jh.core.web.sitemesh;
 
import java.io.IOException;
 
import javax.servlet.http.HttpServletRequest;
 
import org.apache.commons.lang3.StringUtils;
import org.sitemesh.DecoratorSelector;
import org.sitemesh.content.Content;
import org.sitemesh.webapp.WebAppContext;
 
/**
 * 基於request參數decorator值進行動態定位裝飾器的選擇器
 * 若是decorator參數有值，則返回"/WEB-INF/views/layouts/" + decorator + ".jsp"做爲目標裝飾模板頁面
 */
public class ParamDecoratorSelector implements DecoratorSelector<WebAppContext> {
 
    private DecoratorSelector<WebAppContext> defaultDecoratorSelector;
 
    public ParamDecoratorSelector(DecoratorSelector<WebAppContext> defaultDecoratorSelector) {
        this.defaultDecoratorSelector = defaultDecoratorSelector;
    }
 
    public String[] selectDecoratorPaths(Content content, WebAppContext context) throws IOException {
        // build decorator based on the request
        HttpServletRequest request = context.getRequest();
        String decorator = request.getParameter("decorator");
        if (StringUtils.isNotBlank(decorator)) {
            //按照參數值返回對應路徑下面的jsp裝飾模板頁碼
            return new String[] { "/WEB-INF/views/layouts/" + decorator + ".jsp" };
        }
 
        // Otherwise, fallback to the standard configuration
        return defaultDecoratorSelector.selectDecoratorPaths(content, context);
    }
}

<!--   調整web.xml配置：     -->
<filter>
        <filter-name>sitemeshFilter</filter-name>
        <filter-class>lab.s2jh.core.web.sitemesh.ParamConfigurableSiteMeshFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>sitemeshFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>