SpringMVC杂记(十八) ServletRequestAttributes的应用

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>
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