SpringMVC杂记(十八) ServletRequestAttributes的应用

最新推荐文章于 2024-04-29 16:52:01 发布

Outaku

最新推荐文章于 2024-04-29 16:52:01 发布

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本文详细解读了SpringMVC利用ThreadLocal封装HttpServletRequest对象的机制，并通过自定义工具类提供了便捷的使用方式，适用于日常开发场景。

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看了一下SpringMVC的源代码，原来SpringMVC也提供了一个封装过的ThreadLocal保存了每次请求的HttpServletRequest对象，
（详细请看org.springframework.web.context.request.ServletRequestAttributes的源代码）

这下我简单封装一下写了一个工具，用起来还是蛮方便的 :)


package samples.utils;

import java.util.Arrays;
import java.util.Collection;
import java.util.Locale;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import javax.sql.DataSource;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.beans.factory.NoUniqueBeanDefinitionException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.MessageSource;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.ui.context.Theme;
import org.springframework.util.ClassUtils;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import org.springframework.web.context.support.WebApplicationContextUtils;
import org.springframework.web.servlet.LocaleResolver;
import org.springframework.web.servlet.ThemeResolver;
import org.springframework.web.servlet.support.RequestContextUtils;


/**
 * SpringMVC通用工具
 * 
 * @author 应卓(yingzhor@gmail.com)
 *
 */
public final class WebContextHolder {

	private static final Logger LOGGER = LoggerFactory.getLogger(WebContextHolder.class);

	private static final WebContextHolder INSTANCE = new WebContextHolder();

	public WebContextHolder get() {
		return INSTANCE;
	}

	private WebContextHolder() {
		super();
	}

	// --------------------------------------------------------------------------------------------------------------

	public HttpServletRequest getRequest() {
		ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.currentRequestAttributes();
		return attributes.getRequest();
	}

	public HttpSession getSession() {
		return getSession(true);
	}

	public HttpSession getSession(boolean create) {
		return getRequest().getSession(create);
	}

	public String getSessionId() {
		return getSession().getId();
	}

	public ServletContext getServletContext() {
		return getSession().getServletContext();	// servlet2.3
	}

	public Locale getLocale() {
		return RequestContextUtils.getLocale(getRequest());
	}

	public Theme getTheme() {
		return RequestContextUtils.getTheme(getRequest());
	}

	public ApplicationContext getApplicationContext() {
		return WebApplicationContextUtils.getWebApplicationContext(getServletContext());
	}

	public ApplicationEventPublisher getApplicationEventPublisher() {
		return (ApplicationEventPublisher) getApplicationContext();
	}

	public LocaleResolver getLocaleResolver() {
		return RequestContextUtils.getLocaleResolver(getRequest());
	}

	public ThemeResolver getThemeResolver() {
		return RequestContextUtils.getThemeResolver(getRequest());
	}

	public ResourceLoader getResourceLoader() {
		return (ResourceLoader) getApplicationContext();
	}

	public ResourcePatternResolver getResourcePatternResolver() {
		return (ResourcePatternResolver) getApplicationContext();
	}

	public MessageSource getMessageSource() {
		return (MessageSource) getApplicationContext();
	}

	public ConversionService getConversionService() {
		return getBeanFromApplicationContext(ConversionService.class);
	}

	public DataSource getDataSource() {
		return getBeanFromApplicationContext(DataSource.class);
	}

	public Collection<String> getActiveProfiles() {
		return Arrays.asList(getApplicationContext().getEnvironment().getActiveProfiles());
	}

	public ClassLoader getBeanClassLoader() {
		return ClassUtils.getDefaultClassLoader();
	}

	private <T> T getBeanFromApplicationContext(Class<T> requiredType) {
		try {
			return getApplicationContext().getBean(requiredType);
		} catch (NoUniqueBeanDefinitionException e) {
			LOGGER.error(e.getMessage(), e);
			throw e;
		} catch (NoSuchBeanDefinitionException e) {
			LOGGER.warn(e.getMessage());
			return null;
		}
	}

}

当然了必不可少的一点，web.xml里必须要有相应的配置来支持


<listener>
	<listener-class>org.springframework.web.context.request.RequestContextListener</listener-class>
</listener>