org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.java Source code

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/*
 * Copyright 2002-2018 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.mvc.method;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.core.Ordered;
import org.springframework.lang.Nullable;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerAdapter;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.support.WebContentGenerator;

/**
 * Abstract base class for {@link HandlerAdapter} implementations that support
 * handlers of type {@link HandlerMethod}.
 *
 * @author Arjen Poutsma
 * @since 3.1
 */
public abstract class AbstractHandlerMethodAdapter extends WebContentGenerator implements HandlerAdapter, Ordered {

    private int order = Ordered.LOWEST_PRECEDENCE;

    public AbstractHandlerMethodAdapter() {
        // no restriction of HTTP methods by default
        super(false);
    }

    /**
     * Specify the order value for this HandlerAdapter bean.
     * <p>The default value is {@code Ordered.LOWEST_PRECEDENCE}, meaning non-ordered.
     * @see org.springframework.core.Ordered#getOrder()
     */
    public void setOrder(int order) {
        this.order = order;
    }

    @Override
    public int getOrder() {
        return this.order;
    }

    /**
     * This implementation expects the handler to be an {@link HandlerMethod}.
     * @param handler the handler instance to check
     * @return whether or not this adapter can adapt the given handler
     */
    @Override
    public final boolean supports(Object handler) {
        return (handler instanceof HandlerMethod && supportsInternal((HandlerMethod) handler));
    }

    /**
     * Given a handler method, return whether or not this adapter can support it.
     * @param handlerMethod the handler method to check
     * @return whether or not this adapter can adapt the given method
     */
    protected abstract boolean supportsInternal(HandlerMethod handlerMethod);

    /**
     * This implementation expects the handler to be an {@link HandlerMethod}.
     */
    @Override
    @Nullable
    public final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {

        return handleInternal(request, response, (HandlerMethod) handler);
    }

    /**
     * Use the given handler method to handle the request.
     * @param request current HTTP request
     * @param response current HTTP response
     * @param handlerMethod handler method to use. This object must have previously been passed to the
     * {@link #supportsInternal(HandlerMethod)} this interface, which must have returned {@code true}.
     * @return a ModelAndView object with the name of the view and the required model data,
     * or {@code null} if the request has been handled directly
     * @throws Exception in case of errors
     */
    @Nullable
    protected abstract ModelAndView handleInternal(HttpServletRequest request, HttpServletResponse response,
            HandlerMethod handlerMethod) throws Exception;

    /**
     * This implementation expects the handler to be an {@link HandlerMethod}.
     */
    @Override
    public final long getLastModified(HttpServletRequest request, Object handler) {
        return getLastModifiedInternal(request, (HandlerMethod) handler);
    }

    /**
     * Same contract as for {@link javax.servlet.http.HttpServlet#getLastModified(HttpServletRequest)}.
     * @param request current HTTP request
     * @param handlerMethod handler method to use
     * @return the lastModified value for the given handler
     */
    protected abstract long getLastModifiedInternal(HttpServletRequest request, HandlerMethod handlerMethod);

}