Java URL Connection loadLinesUrl(String url)

Description

Load the lines from a remote URL into a list of strings.

License

Open Source License

Parameter

Parameter	Description
url	URL of the resource whose line must be loaded

Return

the list of lines

Declaration

public static List<String> loadLinesUrl(String url) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;

public class Main {
    /**/*  www  .  ja  va 2 s .  c  o  m*/
     * Load the lines from a remote URL into a list of strings.
     * 
     * The remove URL id first downloaded to a local cache file
     * and then read through {@link #loadLines(String) loadLines()}.
     * The local cache copy is used in subsequent operation to
     * avoid multiple download. The cache is updated if the
     * remote file has changed after the file was last downloaded.
     * 
     * @param url URL of the resource whose line must be loaded
     * @return the list of lines
     */
    public static List<String> loadLinesUrl(String url) {
        try {
            URL resource = new URL(url);
            String filename = resource.getFile().replaceAll("/", "_");
            URLConnection conn = resource.openConnection();
            File file = new File(filename);
            if (!file.exists() || file.lastModified() < conn.getLastModified()) {
                byte buffer[] = new byte[4096];
                int n;
                try (InputStream in = conn.getInputStream(); OutputStream out = new FileOutputStream(file)) {
                    while ((n = in.read(buffer)) != -1) {
                        out.write(buffer, 0, n);
                    }
                }
            }
            return loadLines(filename);
        } catch (IOException e) {
            System.err.println("Detected and error while downloading url: " + url);
            return null;
        }
    }

    /**
     * Load the lines from a local text file into a list of strings.
     * 
     * @param file path of the file whose line must be loaded
     * @return the list of lines
     */
    public static List<String> loadLines(String file) {
        ArrayList<String> rows = new ArrayList<>();
        try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
            String line;
            while ((line = reader.readLine()) != null) {
                rows.add(line);
            }
        } catch (IOException e) {
            System.err.println("Detected and error while reading file: " + file);
            return null;
        }
        return rows;
    }
}

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