fetch.java

How to get the java home dir.

package com.mindprod.http;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;

/**
 * Reads with a generic http: https: file: etc, arbitrary URL
 *
 * @author Roedy Green, Canadian Mind Products may be copied and used freely for any purpose but military.
 * @version * 1.9 2008-08-22 support accept-charset, accept-encoding and accept-language.  Fix bugs in gzip support.
 */
@SuppressWarnings( { "WeakerAccess" } )
public final class Fetch extends Http
    {
    // -------------------------- PUBLIC INSTANCE  METHODS --------------------------
    /**
     * constructor
     */
    public Fetch()
        {
        }

    /**
     * Read a message given an URL.  Does not support getResponseCode or getResponseMessage.
     *
     * @param url      complete URL including any parms. Use Request.appendCGIPair to build up parms on the tail end.
     *                 might be http: https: file: and possibly others.
     * @param encoding encoding of the byte stream result, usually UTF-8 or or ISO-8859-1.
     * @return host's response with headers and embedded length fields stripped.
     * @see "com.mindprod.filetransfer.Download"
     */
    @SuppressWarnings( { "UnusedAssignment", "MethodNamesDifferingOnlyByCase" } )
    public String fetch( URL url, String encoding )
        {
        try
            {
            // defaults
            responseCode = DEFAULT_RESPONSE_CODE;
            responseMessage = DEFAULT_RESPONSE_MESSAGE;

            // O P E N
            final URLConnection urlc = url.openConnection();
            // Not actually connecting yet, just getting connection object,
            // urlc will contain  subclasses of URLConnection like:
            // http: HttpURLConnection
            // https: HttpsURLConnectionImpl
            // file: FileURLConnection
            urlc.setAllowUserInteraction( false );
            urlc.setDoInput( true );
            urlc.setDoOutput( false );// nothing beyond original request
            urlc.setUseCaches( false );
            // we leave it up to URLConection to figure out the request method.
            setStandardProperties( urlc );

            urlc.connect();
            // urlConnection does not support   getResponseCode or  getResponseMessage
            // get size of message. -1 means comes in an indeterminate number of chunks.
            int estimatedLength = urlc.getContentLength();
            if ( estimatedLength < 0 )
                {
                // quite common for no length field
                estimatedLength = 32 * 1024;
                }
            final InputStream is = urlc.getInputStream();

            final String contentType = urlc.getContentType();
            //  Content-Type: text/html; charset=utf-8
            int place = contentType.lastIndexOf( "charset=" );
            final String revisedEncoding;
            if ( place >= 0 )
                {
                revisedEncoding = contentType.substring( place + "charset=".length() ).trim().toUpperCase();
                }
            else
                {
                revisedEncoding = encoding;
                }

            // content encoding might be null
            final boolean gzipped = "gzip".equals( urlc.getContentEncoding() )
                                    || "x-gzip".equals( urlc.getContentEncoding() );

            // R E A D
            String result = Read.readStringBlocking( is,
                    estimatedLength,
                    readTimeout,
                    gzipped,
                    revisedEncoding );

            if ( DEBUGGING )
                {
                System.out.println( "--------------------------------" );
                System.out.println( "ContentType:" + contentType );
                System.out.println( "CharSet:" + revisedEncoding );
                System.out.println( "ContentEncoding:" + urlc.getContentEncoding() );
                System.out.println( "Result:" + ( result == null ? "null" : result.substring( 0, Math.min( result.length(), 300 ) ) ) );
                }
            // C L O S E
            is.close();
            // There is no corresponding URLConnection.disconnect
            return result;
            }
        catch ( IOException e )
            {
            return null;
            }
        }// end fetch
    }