学步园

打开Spring的源代码,我们可以在org.springframework.web.servlet.view包下看到很多的
　　View和ViewResolver类;View类为我们提供一些缺省的待扩展的View,如
　　org.springframework.web.servlet.view.document.AbstractExcelView提供了一个缺省的Excel
　　格式的View,org.springframework.web.servlet.view.document.AbstractPdfView提供了一个
　　缺省的pdf格式的View;通过资源文件的配置和ViewResolver的使用,我们可以向用户展示我们自
　　己的各具风格的View.
　　org.springframework.web.servlet.view包下有好几个ViewResolver实现,其中默认采用
　　InternalResourceViewResolver.比如配置文件如下:
　　<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
　　 <property name="viewClass"><value>org.springframework.web.servlet.view.JstlView</value></property>
　　 <property name="prefix"><value>/WEB-INF/jsp/</value></property>
　　 <property name="suffix"><value>.jsp</value></property>
　　</bean>
　　上面的配置表示,将在Controller返回的ModelAndView的基础上,加上目录前缀/WEB-INF/jsp/,
　　加后文件名称后缀.jsp,由此等待下个页面如/WEB-INF/jsp/showCats.jsp
　　另外一种ViewResolver是ResourceBundleViewResolver,比如配置文件如下:
　　<bean id="viewResolver" class="org.springframework.web.servlet.view.ResourceBundleViewResolver">
　　 <property name="basename"><value>views-countries</value></property>
　　 <property name="defaultParentView"><value>modelView</value></property>
　　</bean>
　　basename的配置表示将从classes目录下的views-countries.properties文件中获取资源,这样
　　我们可以很方便的实现国际化与本地化;
　　defaultParentView表示所有的view都将从modelView中继承而来,这和log4j的配置很类似.
　　其它的ViewResolver与上面分析的两种类同

转载自： http://blog.csdn.net/zxs9999/article/details/6904147

参见：http://www.boyunjian.com/javasrc/org.springframework/spring-webmvc/3.2.4.RELEASE/_/org/springframework/web/servlet/view/InternalResourceViewResolver.java

/*
 * Copyright 2002-2012 the original author or authors.
 *
 * 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 org.springframework.web.servlet.view;
 
import org.springframework.util.ClassUtils;
 
/**
 * Convenient subclass of {@link UrlBasedViewResolver} that supports
 * {@link InternalResourceView} (i.e. Servlets and JSPs) and subclasses
 * such as {@link JstlView}.
 *
 * <p>The view class for all views generated by this resolver can be specified
 * via {@link #setViewClass}. See {@link UrlBasedViewResolver}'s javadoc for details.
 * The default is {@link InternalResourceView}, or {@link JstlView} if the
 * JSTL API is present.
 *
 * <p>BTW, it's good practice to put JSP files that just serve as views under
 * WEB-INF, to hide them from direct access (e.g. via a manually entered URL).
 * Only controllers will be able to access them then.
 *
 * <p><b>Note:</b> When chaining ViewResolvers, an InternalResourceViewResolver
 * always needs to be last, as it will attempt to resolve any view name,
 * no matter whether the underlying resource actually exists.
 *
 * @author Juergen Hoeller
 * @since 17.02.2003
 * @see #setViewClass
 * @see #setPrefix
 * @see #setSuffix
 * @see #setRequestContextAttribute
 * @see InternalResourceView
 * @see JstlView
 */
public class InternalResourceViewResolver extends UrlBasedViewResolver {
 
    private static final boolean jstlPresent = ClassUtils.isPresent(
            "javax.servlet.jsp.jstl.core.Config", InternalResourceViewResolver.class.getClassLoader());
 
    private Boolean alwaysInclude;
 
    private Boolean exposeContextBeansAsAttributes;
 
    private String[] exposedContextBeanNames;
 
 
    /**
     * Sets the default {@link #setViewClass view class} to {@link #requiredViewClass}:
     * by default {@link InternalResourceView}, or {@link JstlView} if the JSTL API
     * is present.
     */
    public InternalResourceViewResolver() {
        Class viewClass = requiredViewClass();
        if (viewClass.equals(InternalResourceView.class) && jstlPresent) {
            viewClass = JstlView.class;
        }
        setViewClass(viewClass);
    }
 
    /**
     * This resolver requires {@link InternalResourceView}.
     */
    @Override
    protected Class requiredViewClass() {
        return InternalResourceView.class;
    }
 
 
    /**
     * Specify whether to always include the view rather than forward to it.
     * <p>Default is "false". Switch this flag on to enforce the use of a
     * Servlet include, even if a forward would be possible.
     * @see InternalResourceView#setAlwaysInclude
     */
    public void setAlwaysInclude(boolean alwaysInclude) {
        this.alwaysInclude = Boolean.valueOf(alwaysInclude);
    }
 
    /**
     * Set whether to make all Spring beans in the application context accessible
     * as request attributes, through lazy checking once an attribute gets accessed.
     * <p>This will make all such beans accessible in plain {@code ${...}}
     * expressions in a JSP 2.0 page, as well as in JSTL's {@code c:out}
     * value expressions.
     * <p>Default is "false".
     * @see InternalResourceView#setExposeContextBeansAsAttributes
     */
    public void setExposeContextBeansAsAttributes(boolean exposeContextBeansAsAttributes) {
        this.exposeContextBeansAsAttributes = exposeContextBeansAsAttributes;
    }
 
    /**
     * Specify the names of beans in the context which are supposed to be exposed.
     * If this is non-null, only the specified beans are eligible for exposure as
     * attributes.
     * @see InternalResourceView#setExposedContextBeanNames
     */
    public void setExposedContextBeanNames(String[] exposedContextBeanNames) {
        this.exposedContextBeanNames = exposedContextBeanNames;
    }
 
 
    @Override
    protected AbstractUrlBasedView buildView(String viewName) throws Exception {
        InternalResourceView view = (InternalResourceView) super.buildView(viewName);
        if (this.alwaysInclude != null) {
            view.setAlwaysInclude(this.alwaysInclude);
        }
        if (this.exposeContextBeansAsAttributes != null) {
            view.setExposeContextBeansAsAttributes(this.exposeContextBeansAsAttributes);
        }
        if (this.exposedContextBeanNames != null) {
            view.setExposedContextBeanNames(this.exposedContextBeanNames);
        }
        view.setPreventDispatchLoop(true);
        return view;
    }
 
}