org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer.java Source code

Introduction

Here is the source code for org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer.java

Source

/*
 * Copyright 2002-2019 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
 *
 *      https://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.config.annotation;

import java.util.Collections;
import javax.servlet.ServletContext;

import org.springframework.core.Ordered;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.web.servlet.DispatcherServlet;
import org.springframework.web.servlet.handler.SimpleUrlHandlerMapping;
import org.springframework.web.servlet.resource.DefaultServletHttpRequestHandler;

/**
 * Configures a request handler for serving static resources by forwarding
 * the request to the Servlet container's "default" Servlet. This is intended
 * to be used when the Spring MVC {@link DispatcherServlet} is mapped to "/"
 * thus overriding the Servlet container's default handling of static resources.
 *
 * <p>Since this handler is configured at the lowest precedence, effectively
 * it allows all other handler mappings to handle the request, and if none
 * of them do, this handler can forward it to the "default" Servlet.
 *
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @since 3.1
 * @see DefaultServletHttpRequestHandler
 */
public class DefaultServletHandlerConfigurer {

    private final ServletContext servletContext;

    @Nullable
    private DefaultServletHttpRequestHandler handler;

    /**
     * Create a {@link DefaultServletHandlerConfigurer} instance.
     * @param servletContext the ServletContext to use.
     */
    public DefaultServletHandlerConfigurer(ServletContext servletContext) {
        Assert.notNull(servletContext, "ServletContext is required");
        this.servletContext = servletContext;
    }

    /**
     * Enable forwarding to the "default" Servlet.
     * <p>When this method is used the {@link DefaultServletHttpRequestHandler}
     * will try to autodetect the "default" Servlet name. Alternatively, you can
     * specify the name of the default Servlet via {@link #enable(String)}.
     * @see DefaultServletHttpRequestHandler
     */
    public void enable() {
        enable(null);
    }

    /**
     * Enable forwarding to the "default" Servlet identified by the given name.
     * <p>This is useful when the default Servlet cannot be autodetected,
     * for example when it has been manually configured.
     * @see DefaultServletHttpRequestHandler
     */
    public void enable(@Nullable String defaultServletName) {
        this.handler = new DefaultServletHttpRequestHandler();
        if (defaultServletName != null) {
            this.handler.setDefaultServletName(defaultServletName);
        }
        this.handler.setServletContext(this.servletContext);
    }

    /**
     * Return a handler mapping instance ordered at {@link Ordered#LOWEST_PRECEDENCE}
     * containing the {@link DefaultServletHttpRequestHandler} instance mapped
     * to {@code "/**"}; or {@code null} if default servlet handling was not
     * been enabled.
     * @since 4.3.12
     */
    @Nullable
    protected SimpleUrlHandlerMapping buildHandlerMapping() {
        if (this.handler == null) {
            return null;
        }
        return new SimpleUrlHandlerMapping(Collections.singletonMap("/**", this.handler),
                Ordered.LOWEST_PRECEDENCE);
    }

}