www.pudn.com > 20051122095286.zip > Fetcher.java

package ora.ch6; 
 
import java.io.InputStream; 
import java.io.IOException; 
import java.io.OutputStream; 
import javax.microedition.io.Connector; 
import javax.microedition.io.HttpConnection; 
 
public class Fetcher { 
 
    private static final String BASE_URL = "http://www.amazon.com"; 
    private static final String QUERY_URL = BASE_URL + 
                                "/exec/obidos/search-handle-form/0"; 
 
    private static final int MAX_REDIRECTS = 5; 
 
    // Fetches the title, ranking and review count 
    // for a book with a given ISBN. 
    public static boolean fetch(BookInfo info) throws IOException { 
        InputStream is = null; 
        OutputStream os = null; 
        HttpConnection conn = null; 
        int redirects = 0; 
        try { 
            String isbn = info.getIsbn(); 
            String query = "index=books&field-keywords=" + isbn + "\r\n"; 
            String requestMethod = HttpConnection.POST; 
            String name = QUERY_URL; 
 
            while (redirects < MAX_REDIRECTS) { 
                conn = (HttpConnection)Connector.open(name, 
                                                    Connector.READ_WRITE); 
 
                // Send the ISBN number to perform the query 
                conn.setRequestMethod(requestMethod); 
                conn.setRequestProperty("Connection", "Close"); 
                if (requestMethod.equals(HttpConnection.POST)) { 
                    conn.setRequestProperty("Content-Type", 
                                "application/x-www-form-urlencoded"); 
                    os = conn.openOutputStream(); 
                    os.write(query.getBytes()); 
                    os.close(); 
                    os = null;                     
                } 
 
                // Read the response from the server 
                is = conn.openInputStream(); 
                int code = conn.getResponseCode(); 
 
                // If we get a redirect, try again at the new location 
                if ((code >= HttpConnection.HTTP_MOVED_PERM && 
                        code <= HttpConnection.HTTP_SEE_OTHER) || 
                        code == HttpConnection.HTTP_TEMP_REDIRECT) { 
                    // Get the URL of the new location (always absolute) 
                    name = conn.getHeaderField("Location"); 
                    is.close(); 
                    conn.close(); 
                    is = null; 
                    conn = null; 
 
                    if (++redirects > MAX_REDIRECTS) { 
                        // Too many redirects - give up. 
                        break; 
                    } 
 
                    // Choose the appropriate request method 
                    requestMethod = HttpConnection.POST; 
                    if (code == HttpConnection.HTTP_MOVED_TEMP || 
                            code == HttpConnection.HTTP_SEE_OTHER) { 
                        requestMethod = HttpConnection.GET; 
                    } 
                    continue; 
                } 
                String type = conn.getType(); 
                if (code == HttpConnection.HTTP_OK && 
                                    type.equals("text/html")) { 
                    info.setFromInputStream(is); 
                    return true; 
                } 
            } 
        } catch (Throwable t) { 
            System.out.println(t); 
        } finally { 
            if (is != null) { 
                try { 
                    is.close(); 
                } catch (IOException ex) { 
                } 
            } 
            if (os != null) { 
                try { 
                    os.close(); 
                } catch (IOException ex) { 
                } 
            } 
            if (conn != null) { 
                try { 
                    conn.close(); 
                } catch (IOException ex) { 
                } 
            }             
        } 
        return false; 
    } 
}