HttpUtil.java

package de.axone.tools;

import java.io.IOException;
import java.io.InputStream;
import java.net.URISyntaxException;
import java.net.URL;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.http.Header;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;

import de.axone.file.Slurper;


public class HttpUtil {
	
	public static class HttpUtilResponse {
		
		public int code = -1;
		public String eTag;
		public String lastModified;
		public long maxAge = -1;
		public byte[] content;
		public String encoding;
		
		@Override
		public String toString(){
			return 
				"code: " + code + "\n" +
				"etag: " + eTag + "\n" +
				"maxAge: " + maxAge + "\n" +
				"size: " + (content != null ? content.length : 0)
			;
		}

	}
	
	public static String printHttpInfo( HttpGet httpget, HttpResponse response ){
		
		StringBuilder result = new StringBuilder();
		
		result.append( "HTTP-INFO\n\n" );
		result.append( "Request: " );
		result.append( httpget.getURI().toString() + "\n" );
		for( Header header: httpget.getAllHeaders() ){
			result.append( "  " + header.getName() + ": " + header.getValue() + "\n" );
		}
		result.append( "Response: " );
		result.append( response.getStatusLine() + "\n" );
		for( Header header: response.getAllHeaders() ){
			result.append( "  " + header.getName() + ": " + header.getValue() + "\n" );
		}
		
		return result.toString();
	}

	public static HttpUtilResponse request( URL url, String eTag, String lastModified ) throws URISyntaxException, ClientProtocolException, IOException{
		
		HttpClientBuilder builder = HttpClientBuilder.create();
		
		try( CloseableHttpClient client = builder.build() ){
			
			HttpGet httpget = new HttpGet( url.toURI() );
			if( eTag != null ){
				httpget.setHeader( "If-None-Match", eTag );
			}
			if( lastModified != null ){
				httpget.setHeader( "If-Modified-Since", lastModified );
			}
			
			try( CloseableHttpResponse response = client.execute( httpget ) ){
				
				//E.poster( printHttpInfo( httpget, response ) );
				
				HttpUtilResponse uResponse = new HttpUtilResponse();
				uResponse.code = response.getStatusLine().getStatusCode();
				
				// break here if not modified
				if( uResponse.code == 304 ) return uResponse;
				
				if( uResponse.code == 200 ){
					
					Header [] eTags = response.getHeaders( "ETag" );
					if( eTags != null && eTags.length > 0 ){
						uResponse.eTag = eTags[ eTags.length-1 ].getValue();
					}
					Header [] lastModifieds = response.getHeaders( "Last-Modified" );
					if( lastModifieds != null && lastModifieds.length > 0 ){
						uResponse.lastModified = lastModifieds[ lastModifieds.length-1 ].getValue();
					}
					
					Header cacheControl = response.getLastHeader( "Cache-Control" );
					if( cacheControl != null ){
						Pattern pattern = Pattern.compile( "max-age=([0-9]+)" );
						Matcher matcher = pattern.matcher( cacheControl.getValue() );
						if( matcher.find() ){
							String maxAgeGroup = matcher.group();
							String maxAgeString = maxAgeGroup.substring( maxAgeGroup.indexOf( '=' )+1 );
							uResponse.maxAge = Long.parseLong( maxAgeString );
						}
					}
					
					Header contentType = response.getLastHeader( "Content-Type" );
					if( contentType != null ){
						
						Pattern pattern = Pattern.compile( ".*; *charset=(.+)" );
						Matcher matcher = pattern.matcher( contentType.getValue() );
						if( matcher.find() ){
							//uResponse.encoding = found.substring( found.indexOf( "=" )+1 );
							uResponse.encoding = matcher.group(1).trim();
						}
					}
					
					HttpEntity entity = response.getEntity();
					
					try( InputStream in = entity.getContent() ){
						byte [] content = Slurper.slurp( in );
						uResponse.content = content;
					}
					
				}
				return uResponse;
			}
		}
	}
}