springMVC源码分析--动态样式ThemeResolver（二）

àì夳堔傛蜴生んèń 2022-07-14 09:51 210阅读 0赞

在上一篇博客[springMVC源码分析--动态样式ThemeResolver（一）][springMVC_--_ThemeResolver]中我们介绍了多样式ThemeResolver的使用方法，接下来我们对源码进行简单的分析一下。

ThemeResolver的体系结构如下：

![Image 1][]

1、接口ThemeResolver中定义的接口是比较简单的，提供两个接口：

（1）resolveThemeName获取样式名

（2）setThemeName设置样式名

public interface ThemeResolver {
    
    	/**
    	 * Resolve the current theme name via the given request.
    	 * Should return a default theme as fallback in any case.
    	 * @param request request to be used for resolution
    	 * @return the current theme name
    	 */
    	String resolveThemeName(HttpServletRequest request);
    
    	/**
    	 * Set the current theme name to the given one.
    	 * @param request request to be used for theme name modification
    	 * @param response response to be used for theme name modification
    	 * @param themeName the new theme name
    	 * @throws UnsupportedOperationException if the ThemeResolver implementation
    	 * does not support dynamic changing of the theme
    	 */
    	void setThemeName(HttpServletRequest request, HttpServletResponse response, String themeName);
    
    }

2、抽象类AbstractThemeResolver，提供两个方法：

（1）setDefaultThemeName 设置默认的样式名

（2）getDefaultThemeName 获取默认的样式名

public abstract class AbstractThemeResolver implements ThemeResolver {
    
    	public final static String ORIGINAL_DEFAULT_THEME_NAME = "theme";
    
    	private String defaultThemeName = ORIGINAL_DEFAULT_THEME_NAME;
    
    	public void setDefaultThemeName(String defaultThemeName) {
    		this.defaultThemeName = defaultThemeName;
    	}
    
    	public String getDefaultThemeName() {
    		return this.defaultThemeName;
    	}
    
    }

3、实现类CookieThemeResolver，其实现原理其实是比较简单的，就是在Cookie中设置样式名

（1）在setThemeName函数中中将theme设置到cookie中

public class CookieThemeResolver extends CookieGenerator implements ThemeResolver {
    
    	public final static String ORIGINAL_DEFAULT_THEME_NAME = "theme";
    
    	/**
    	 * Name of the request attribute that holds the theme name. Only used
    	 * for overriding a cookie value if the theme has been changed in the
    	 * course of the current request! Use RequestContext.getTheme() to
    	 * retrieve the current theme in controllers or views.
    	 * @see org.springframework.web.servlet.support.RequestContext#getTheme
    	 */
    	public static final String THEME_REQUEST_ATTRIBUTE_NAME = CookieThemeResolver.class.getName() + ".THEME";
    
    	public static final String DEFAULT_COOKIE_NAME = CookieThemeResolver.class.getName() + ".THEME";
    
    
    	private String defaultThemeName = ORIGINAL_DEFAULT_THEME_NAME;
    
    
    	public CookieThemeResolver() {
    		setCookieName(DEFAULT_COOKIE_NAME);
    	}
    
    
    	/**
    	 * Set the name of the default theme.
    	 */
    	public void setDefaultThemeName(String defaultThemeName) {
    		this.defaultThemeName = defaultThemeName;
    	}
    
    	/**
    	 * Return the name of the default theme.
    	 */
    	public String getDefaultThemeName() {
    		return defaultThemeName;
    	}
    
    
    	@Override
    	public String resolveThemeName(HttpServletRequest request) {
    		// Check request for preparsed or preset theme.
    		String themeName = (String) request.getAttribute(THEME_REQUEST_ATTRIBUTE_NAME);
    		if (themeName != null) {
    			return themeName;
    		}
    
    		// Retrieve cookie value from request.
    		Cookie cookie = WebUtils.getCookie(request, getCookieName());
    		if (cookie != null) {
    			String value = cookie.getValue();
    			if (StringUtils.hasText(value)) {
    				themeName = value;
    			}
    		}
    
    		// Fall back to default theme.
    		if (themeName == null) {
    			themeName = getDefaultThemeName();
    		}
    		request.setAttribute(THEME_REQUEST_ATTRIBUTE_NAME, themeName);
    		return themeName;
    	}
    
    	@Override
    	public void setThemeName(HttpServletRequest request, HttpServletResponse response, String themeName) {
    		if (StringUtils.hasText(themeName)) {
    			// Set request attribute and add cookie.
    			request.setAttribute(THEME_REQUEST_ATTRIBUTE_NAME, themeName);
    			addCookie(response, themeName);
    		}
    		else {
    			// Set request attribute to fallback theme and remove cookie.
    			request.setAttribute(THEME_REQUEST_ATTRIBUTE_NAME, getDefaultThemeName());
    			removeCookie(response);
    		}
    	}
    
    }

3、实现类SessionThemeResolver的实现也是比较简单的，就是将themeName保存到session中就可以了。

public class SessionThemeResolver extends AbstractThemeResolver {
    
    	/**
    	 * Name of the session attribute that holds the theme name.
    	 * Only used internally by this implementation.
    	 * Use {@code RequestContext(Utils).getTheme()}
    	 * to retrieve the current theme in controllers or views.
    	 * @see org.springframework.web.servlet.support.RequestContext#getTheme
    	 * @see org.springframework.web.servlet.support.RequestContextUtils#getTheme
    	 */
    	public static final String THEME_SESSION_ATTRIBUTE_NAME = SessionThemeResolver.class.getName() + ".THEME";
    
    
    	@Override
    	public String resolveThemeName(HttpServletRequest request) {
    		String themeName = (String) WebUtils.getSessionAttribute(request, THEME_SESSION_ATTRIBUTE_NAME);
    		// A specific theme indicated, or do we need to fallback to the default?
    		return (themeName != null ? themeName : getDefaultThemeName());
    	}
    
    	@Override
    	public void setThemeName(HttpServletRequest request, HttpServletResponse response, String themeName) {
    		WebUtils.setSessionAttribute(request, THEME_SESSION_ATTRIBUTE_NAME,
    				(StringUtils.hasText(themeName) ? themeName : null));
    	}
    
    }

4、FixedThemeResolver中没有具体的实现操作

public class FixedThemeResolver extends AbstractThemeResolver {
    
    	@Override
    	public String resolveThemeName(HttpServletRequest request) {
    		return getDefaultThemeName();
    	}
    
    	@Override
    	public void setThemeName(HttpServletRequest request, HttpServletResponse response, String themeName) {
    		throw new UnsupportedOperationException("Cannot change theme - use a different theme resolution strategy");
    	}
    
    }

[springMVC_--_ThemeResolver]: http://blog.csdn.net/qq924862077/article/details/53438710
[Image 1]: