com.feilong.spring.web.util.WebSpringUtil Maven / Gradle / Ivy
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/*
* Copyright (C) 2008 feilong
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.feilong.spring.web.util;
import javax.servlet.ServletContext;
import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.context.ApplicationContext;
import org.springframework.web.context.WebApplicationContext;
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.DispatcherServlet;
import org.springframework.web.servlet.FrameworkServlet;
import org.springframework.web.servlet.support.RequestContextUtils;
import com.feilong.core.Validate;
/**
* {@link WebApplicationContextUtils} 工具类.
*
*
* 当 Web应用集成 Spring容器后,代表 Spring 容器的 {@link WebApplicationContext} 对象将以{@link WebApplicationContext#ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE}
* 为键存放在 {@link ServletContext} 属性列表中,具体参见 {@link org.springframework.web.context.ContextLoader#initWebApplicationContext(ServletContext)}
*
*
* {@link WebApplicationContextUtils#getWebApplicationContext(ServletContext)}VS
* {@link RequestContextUtils#getWebApplicationContext(javax.servlet.ServletRequest)}:
*
*
*
* 注意: {@link WebApplicationContext#ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE} 存放的是spring ApplicationContext而非 springmvc ApplicationContext
*
*
* {@link RequestContextUtils#getWebApplicationContext(javax.servlet.ServletRequest)}可以取到 springmvc ApplicationContext,他的原理是,每次
*
* {@link DispatcherServlet#doService(HttpServletRequest, HttpServletResponse)} 都会往request里面设置 key为
* {@link DispatcherServlet#WEB_APPLICATION_CONTEXT_ATTRIBUTE} 的属性,而此时的值 WebApplicationContext是通过
* {@link FrameworkServlet#initWebApplicationContext()} 初始化的; 具体参见 {@link FrameworkServlet#createWebApplicationContext(ApplicationContext)}
* ,可以明显看出spring ApplicationContext是 springmvc ApplicationContext 的parent
*
*
*
*
* {@link WebApplicationContextUtils#getWebApplicationContext(ServletContext) getWebApplicationContext}VS
* {@link WebApplicationContextUtils#getRequiredWebApplicationContext(ServletContext) getRequiredWebApplicationContext}:
*
*
* 当 ServletContext 属性列表中不存在 WebApplicationContext时:
*
* - {@link WebApplicationContextUtils#getWebApplicationContext(ServletContext)}方法不会抛出异常,它简单地返回 null, 如果后续代码直接访问返回的结果将引发一个
* NullPointerException 异常.
* - 而{@link WebApplicationContextUtils#getRequiredWebApplicationContext(ServletContext)}方法要求 ServletContext属性列表中一定要包含一个有效的
* WebApplicationContext对象,否则马上抛出一个 异常 {@link java.lang.IllegalStateException}.
*
* 我们推荐使用后者,因为它能提前发现错误的时间,强制开发者搭建好必备的基础设施.
*
*
*
* @author feilong
* @see org.springframework.web.context.WebApplicationContext#ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE
* @see org.springframework.web.context.support.WebApplicationContextUtils#getWebApplicationContext(ServletContext)
* @since 3.0.2 move from feilong-spring project
*/
public final class WebSpringUtil{
/** Don't let anyone instantiate this class. */
private WebSpringUtil(){
//AssertionError不是必须的. 但它可以避免不小心在类的内部调用构造器. 保证该类在任何情况下都不会被实例化.
//see 《Effective Java》 2nd
throw new AssertionError("No " + getClass().getName() + " instances for you!");
}
//---------------------------------------------------------------
/**
* 获得 request.
*
* 说明:
*
*
* spring 3中可以通过 {@link RequestContextHolder} 得到 {@link HttpServletRequest},但是得不到 {@link HttpServletResponse},具体参见
* {@link WebSpringUtil.getResponse()方法获取到的response是null}
*
*
*
* @return the request
* @see Spring MVC的RequestContextHolder使用误区
* @see springMVC 中几种获取request和response的方式
* @see How to obtain the HttpServletResponse Spring AOP?
* @see RequestContextHolder#getRequestAttributes()
* @see ServletRequestAttributes#getRequest()
* @see org.springframework.web.servlet.mvc.method.annotation.ServletRequestMethodArgumentResolver
* @see org.springframework.web.util.WebUtils#getNativeRequest(ServletRequest, Class)
* @since 1.10.0
*/
public static HttpServletRequest getRequest(){
ServletRequestAttributes servletRequestAttributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
return servletRequestAttributes.getRequest();
}
//---------------------------------------------------------------
/**
* 普通类获得spring 注入的类方法.
*
*
* 此方法底层调用的是 {@link RequestContextUtils#getWebApplicationContext(ServletRequest, ServletContext)} ,会从spingmvc 以及spring
* ApplicationContext 查找bean
*
*
* @param
* the generic type
* @param request
* request
* @param beanName
* xml文件中配置的bean beanName
* @return 先在servlet-specific {@link WebApplicationContext} 里面找 bean;
* 如果没有,会在 global context里面找;
* 如果在servlet-specific 或者 global context 都找不到,会抛出 {@link IllegalStateException}
* @see #getWebApplicationContext(HttpServletRequest)
* @see RequestContextUtils#getWebApplicationContext(ServletRequest, ServletContext)
*/
public static T getBean(HttpServletRequest request,String beanName){
WebApplicationContext webApplicationContext = getWebApplicationContext(request);
return getBean(webApplicationContext, beanName);
}
/**
* Gets the bean.
*
*
* 此方法底层调用的是 {@link RequestContextUtils#getWebApplicationContext(ServletRequest,
* ServletContext)} ,会从spingmvc 以及spring ApplicationContext 查找bean
*
*
* @param
* the generic type
* @param request
* the request
* @param requiredType
* the required type
* @return 先在servlet-specific {@link WebApplicationContext} 里面找 bean;
* 如果没有,会在 global context里面找;
* 如果在servlet-specific 或者 global context 都找不到,会抛出 {@link IllegalStateException}
* @see #getWebApplicationContext(HttpServletRequest)
* @see RequestContextUtils#getWebApplicationContext(ServletRequest, ServletContext)
*/
public static T getBean(HttpServletRequest request,Class requiredType){
WebApplicationContext webApplicationContext = getWebApplicationContext(request);
return getBean(webApplicationContext, requiredType);
}
//---------------------------------------------------------------
/**
* 普通类获得spring 注入的类方法.
*
*
* 注意:(如果找不到bean,返回null).
*
*
* @param
* the generic type
* @param servletContext
* servletContext
* @param beanName
* xml文件中配置的bean beanName
* @return 注入的bean
* @see #getWebApplicationContext(ServletContext)
*/
public static T getBean(ServletContext servletContext,String beanName){
WebApplicationContext webApplicationContext = getWebApplicationContext(servletContext);
return getBean(webApplicationContext, beanName);
}
/**
* Gets the bean.
*
* @param
* the generic type
* @param servletContext
* the servlet context
* @param requiredType
* the required type
* @return the bean
*/
public static T getBean(ServletContext servletContext,Class requiredType){
WebApplicationContext webApplicationContext = getWebApplicationContext(servletContext);
return getBean(webApplicationContext, requiredType);
}
//---------------------------------------------------------------
/**
* Gets the required bean.
*
* @param
* the generic type
* @param servletContext
* the servlet context
* @param beanName
* the bean name
* @return the required bean
* @see #getRequiredWebApplicationContext(ServletContext)
*/
public static T getRequiredBean(ServletContext servletContext,String beanName){
WebApplicationContext webApplicationContext = getRequiredWebApplicationContext(servletContext);
return getBean(webApplicationContext, beanName);
}
/**
* Gets the required bean.
*
* @param
* the generic type
* @param servletContext
* the servlet context
* @param requiredType
* the required type
* @return the required bean
* @see #getRequiredWebApplicationContext(ServletContext)
*/
public static T getRequiredBean(ServletContext servletContext,Class requiredType){
WebApplicationContext webApplicationContext = getRequiredWebApplicationContext(servletContext);
return getBean(webApplicationContext, requiredType);
}
//---------------------------------------------------------------
/**
* Gets the bean.
*
* @param
* the generic type
* @param applicationContext
* the application context
* @param beanName
* the bean name
* @return NoSuchBeanDefinitionException - if there is no bean definition with the specified name
*/
@SuppressWarnings("unchecked")
private static T getBean(ApplicationContext applicationContext,String beanName){
return (T) applicationContext.getBean(beanName);
}
/**
* Gets the bean.
*
* @param
* the generic type
* @param applicationContext
* the application context
* @param requiredType
* the required type
* @return the bean
*/
private static T getBean(ApplicationContext applicationContext,Class requiredType){
return applicationContext.getBean(requiredType);
}
//---------------------------------------------------------------
/**
* Find the root {@link WebApplicationContext} for this web app, typically loaded via
* {@link org.springframework.web.context.ContextLoaderListener}.
*
* Will rethrow an exception that happened on root context startup,
* to differentiate between a failed context startup and no context at all.
*
* @param servletContext
* the servlet context
* @return the root WebApplicationContext for this web app, or {@code null} if none
* @see org.springframework.web.context.WebApplicationContext#ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE
* @see org.springframework.web.context.support.WebApplicationContextUtils#getWebApplicationContext(ServletContext)
* @since 1.1.1
*/
public static WebApplicationContext getWebApplicationContext(ServletContext servletContext){
return WebApplicationContextUtils.getWebApplicationContext(servletContext);
}
/**
* 获得 web application context.
*
* @param servletContext
* the servlet context
* @return the web application context
* @see org.springframework.web.context.WebApplicationContext#ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE
* @see org.springframework.web.context.support.WebApplicationContextUtils#getRequiredWebApplicationContext(ServletContext)
* @since 1.2.0
*/
public static WebApplicationContext getRequiredWebApplicationContext(ServletContext servletContext){
return WebApplicationContextUtils.getRequiredWebApplicationContext(servletContext);
}
/**
* 获得 web application context.
*
*
* 此方法可以得到springmvc 的bean
*
*
* @param request
* the request
* @return 如果有 servlet-specific WebApplicationContext那么返回;
* 否则找 global context;
* 两个都没有 会抛出 IllegalStateException
* @see org.springframework.web.servlet.support.RequestContextUtils#getWebApplicationContext(ServletRequest)
* @since 1.5.3
*/
public static WebApplicationContext getWebApplicationContext(HttpServletRequest request){
Validate.notNull(request, "request can't be null!");
//Gets the servlet context to which this ServletRequest was last dispatched.
//since Servlet 3.0
ServletContext servletContext = request.getServletContext();
Validate.notNull(servletContext, "servletContext can't be null!,request class is:[%s]", request.getClass().getName());
//内部调用了 WebApplicationContextUtils.getRequiredWebApplicationContext(ServletContext)
//since spring 4.2.1 原 org.springframework.web.servlet.support.RequestContextUtils.getWebApplicationContext(ServletRequest, ServletContext) 方法
return RequestContextUtils.findWebApplicationContext(request, servletContext);
}
}