HTTPCacheContext.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.tuscany.sca.common.http;

import java.text.SimpleDateFormat;
import java.util.Date;

import javax.servlet.http.HttpServletRequest;

/**
 * A class to store cache settings for Atom and HTTP requests and responses.
 * 
 * Predicates are statements that work in conjunction with
 * ETags and LastModified dates to determine if a precondition
 * or postcondition is satisfied.
 * See HTTP specification for how predicates wrk:
 * http://tools.ietf.org/html/rfc2616
 * Example predicates in HTTP include If-Match, If-None-Match,
 * If-Modified-Since, If-Unmodified-Since, If-Range.
 * 
 * @version $Rev$ $Date$
 */
public class HTTPCacheContext {
    public static final SimpleDateFormat RFC822DateFormat = new SimpleDateFormat( "EEE, dd MMM yyyy HH:mm:ss Z" ); // RFC 822 date time

    public boolean enabled;
    public String eTag;
    public String lastModified;
    public Date lastModifiedDate;
    public boolean ifModifiedSince;
    public boolean ifUnmodifiedSince;
    public boolean ifMatch;
    public boolean ifNoneMatch;
    public boolean ifRange;

    /**
     * Gets the cache context information (ETag, LastModified, predicates) from the Http request.
     * @param request
     * @return
     */
    public static HTTPCacheContext createCacheContextFromRequest( HttpServletRequest request ) throws java.text.ParseException {
        HTTPCacheContext context = new HTTPCacheContext();

        String eTag = request.getHeader( "If-Match" );          
        if ( eTag != null ) {
            context.setETag( eTag );
            context.setIfMatch( true );
        }
        eTag = request.getHeader( "If-None-Match" );            
        if ( eTag != null ) {
            context.setETag( eTag );
            context.setIfNoneMatch( true );
        }
        String lastModifiedString = request.getHeader( "If-Modified-Since" );        
        if ( lastModifiedString != null ) {
            context.setLastModified( lastModifiedString );
            context.setIfModifiedSince( true );
        }
        lastModifiedString = request.getHeader( "If-Unmodified-Since" );        
        if ( lastModifiedString != null ) {
            context.setLastModified( lastModifiedString );
            context.setIfUnmodifiedSince( true );
        }
        lastModifiedString = request.getHeader( "If-Range" );        
        if ( lastModifiedString != null ) {
            context.setLastModified( lastModifiedString );
            context.setIfRange( true );
        }
        return context;
    }
    
    /**
     * Enabled is true whenever ETag, LastModified, or predicate is set.
     * @return the enabled
     */
    public boolean isEnabled() {
        return enabled;
    }
    
    /**
     * @param enabled the enabled to set
     */
    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }
    
    /**
     * An ETag is a unique ID for an item. It changes when
     * a field in the item or the update date changes.
     * See HTTP specification for how ETags work:
     * http://tools.ietf.org/html/rfc2616
     * @return the eTag
     */
    public String getETag() {
        return eTag;
    }
    /**
     * @param tag the eTag to set
     */
    public void setETag(String tag) {
        eTag = tag;
        enabled = true;
    }
    /**
     * The LastModified date is the time the item was last 
     * changed. See HTTP specification for how ETags work:
     * http://tools.ietf.org/html/rfc2616
     * @return the lastModified
     */
    public String getLastModified() {
        return lastModified;
    }
    /**
     * The LastModified date is the time the item was last 
     * changed. See HTTP specification for how ETags work:
     * http://tools.ietf.org/html/rfc2616
     * @return the lastModified
     */
    public Date getLastModifiedAsDate() {
        return lastModifiedDate;
    }
    /**
     * @param lastModified the lastModified to set
     */
    public void setLastModified(String lastModified) throws java.text.ParseException {
        this.lastModified = lastModified;
        // Catch date formatting on input to help debugging.
        lastModifiedDate = RFC822DateFormat.parse( lastModified );
        enabled = true;
    }

    /**
     * @param lastModified the lastModified to set
     */
    public void setLastModified(Date updated) {
        this.lastModified = RFC822DateFormat.format( updated );
        lastModifiedDate = updated;
        enabled = true;
    }

    /**
     * @return the ifModifedSince
     */
    public boolean isIfModifiedSince() {
        return ifModifiedSince;
    }
    /**
     * @param ifModifedSince the ifModifedSince to set
     */
    public void setIfModifiedSince(boolean ifModifiedSince) {
        this.ifModifiedSince = ifModifiedSince;
        if ( ifModifiedSince )
            enabled = true;
    }
    /**
     * @return the ifUnModifiedSince
     */
    public boolean isIfUnmodifiedSince() {
        return ifUnmodifiedSince;
    }
    /**
     * @param ifUnModifiedSince the ifUnModifiedSince to set
     */
    public void setIfUnmodifiedSince(boolean ifUnmodifiedSince) {
        this.ifUnmodifiedSince = ifUnmodifiedSince;
        if ( ifUnmodifiedSince )
            enabled = true;
    }
    /**
     * @return the ifMatch
     */
    public boolean isIfMatch() {
        return ifMatch;
    }
    /**
     * @param ifMatch the ifMatch to set
     */
    public void setIfMatch(boolean ifMatch) {
        this.ifMatch = ifMatch;
        if ( ifMatch )
            enabled = true;
    }
    /**
     * @return the ifNoneMatch
     */
    public boolean isIfNoneMatch() {
        return ifNoneMatch;
    }
    /**
     * @param ifNoneMatch the ifNoneMatch to set
     */
    public void setIfNoneMatch(boolean ifNoneMatch) {
        this.ifNoneMatch = ifNoneMatch;
        if ( ifNoneMatch )
            enabled = true;
    }
    /**
     * @return the ifRange
     */
    public boolean isIfRange() {
        return ifRange;
    }
    /**
     * @param ifRange the ifRange to set
     */
    public void setIfRange(boolean ifRange) {
        this.ifRange = ifRange;
        if ( ifRange )
            enabled = true;
    }

    public String toString() {
        final String PREDPREFIX = ", predicates=";
        StringBuffer sb = new StringBuffer(PREDPREFIX);
        if ( ifMatch || ifNoneMatch || ifModifiedSince || ifUnmodifiedSince || ifRange ) {
            if ( ifMatch ) {
                if ( sb.length() > PREDPREFIX.length() ) sb.append( ", ");
                sb.append("If-Match");
            }
            if ( ifNoneMatch ) {
                if ( sb.length() > PREDPREFIX.length() ) sb.append( ", ");
                sb.append("If-None-Match");
            }
            if ( ifModifiedSince ) {
                if ( sb.length() > PREDPREFIX.length() ) sb.append( ", ");
                sb.append("If-Modified-Since");
            }
            if ( ifUnmodifiedSince ) {
                if ( sb.length() > PREDPREFIX.length() ) sb.append( ", ");
                sb.append("If-UnModified-Since");
            }
            if ( ifRange ) {
                if ( sb.length() > PREDPREFIX.length() ) sb.append( ", ");
                sb.append("If-Range");
            }
        } else {
            sb.append("null");
        }

        return "eTag=" + eTag + ", lastModified=" + lastModified
        + sb.toString();
    }

}