From 1733a1a4aa6ad40446fe6f915577d1270b1e9802 Mon Sep 17 00:00:00 2001
From: Martin Goik <goik@hdm-stuttgart.de>
Date: Wed, 25 Nov 2015 20:23:18 +0100
Subject: [PATCH] Better HTTP response handling, using Java streams
---
Doc/Sda1/dom.xml | 96 ++++++++++---------
.../{src/main/resources => }/fileextref.html | 10 +-
P/Sda1/VerifyImgAccess/pom.xml | 8 ++
.../main/java/dom/xpath/CheckExtImage.java | 18 ++--
.../java/dom/xpath/CheckExtImageDriver.java | 2 +-
.../src/main/java/dom/xpath/CheckUrl.java | 44 ++++++---
.../src/main/resources/log4j2.xml | 4 +-
.../src/test/java/alignimg/TestImgSearch.java | 29 ++++--
8 files changed, 126 insertions(+), 85 deletions(-)
rename P/Sda1/VerifyImgAccess/{src/main/resources => }/fileextref.html (71%)
diff --git a/Doc/Sda1/dom.xml b/Doc/Sda1/dom.xml
index b7822ef32..1769014ad 100644
--- a/Doc/Sda1/dom.xml
+++ b/Doc/Sda1/dom.xml
@@ -1560,22 +1560,27 @@ public class DomXpath {
<programlisting language="xml"
xml:id="domCheckImageAccessibility"><!DOCTYPE html>
-<html xmlns="http://www.w3.org/1999/xhtml">
- <head> ... </head>
+<html xmlns="http://www.w3.org/1999/xhtml">
+ <head>
+ <title>External Pictures</title>
+ </head>
<body>
<h1>External Pictures</h1>
<p>A local image reference:<img src="inline.gif" alt="none"/></p>
+ <p>What about ftp?<img src="ftp://inexistent.com/q.png" alt="none"/></p>
<table>
<tbody>
<tr>
<td>An existing picture:</td>
- <td><img
- src="http://www.hdm-stuttgart.de/bilder_navigation/laptop.gif"
- alt="none"/></td>
+ <td><img
+ src="https://www.hdm-stuttgart.de/bilder_navigation/laptop.gif"
+ alt="none"/></td>
</tr>
<tr>
<td>A non-existing picture:</td>
- <td><img src="<emphasis role="bold">http://www.hdm-stuttgart.de/rotfl.gif</emphasis>" alt="none"/></td>
+ <td><img
+ src="http://www.hdm-stuttgart.de/rotfl.gif"
+ alt="none"/></td>
</tr>
</tbody>
</table>
@@ -1586,51 +1591,40 @@ public class DomXpath {
<abbrev
xlink:href="http://www.ietf.org/rfc/rfc1738.txt">URL</abbrev>
image references to <emphasis>external</emphasis> Servers
- starting either with <code>http://</code> ,
- <code>https://</code> or <code>ftp://</code> ignoring other
- protocol types. Internal image references referring to the
- <quote>current</quote> server typically look like <code><img
- src="/images/test.gif"</code>. So in order to distinguish these
- two types of references we may use the XSL built in function
- <link
+ starting either with <code>http://</code> or
+ <code>https://</code> ignoring other protocol types. Internal
+ image references referring to the <quote>current</quote> server
+ typically look like <code><img src="/images/test.gif"</code>.
+ So in order to distinguish these two types of references we may
+ use the XSL built in function <link
xlink:href="http://www.cafeconleche.org/books/bible2/chapters/ch17.html">starts-with()</link>
- testing for the <code>http</code> or <code>ftp</code> protocol
+ testing for the <code>http</code> or <code>https</code> protocol
definition part of an <abbrev
xlink:href="http://www.ietf.org/rfc/rfc1738.txt">URL</abbrev>. A
possible output for the example being given is:</para>
- <programlisting language="none">Received 'sun.awt.image.URLImageSource' from
- http://www.hdm-stuttgart.de/bilder_navigation/laptop.gif
-Unable to open 'http://www.hdm-stuttgart.de/rotfl.gif'</programlisting>
+ <programlisting language="none">xpath.CheckUrl (CheckUrl.java:51) - Protocol 'ftp' not yet implemented
+ftp://inexistent.com/q.png, HTTP Status: null
+https://www.hdm-stuttgart.de/bilder_navigation/laptop.gif, HTTP Status: OK
+http://www.hdm-stuttgart.de/rotfl.gif, HTTP Status: Found</programlisting>
- <para>The following code snippet shows a helpful class method to
- check for both correctness of <abbrev
- xlink:href="http://www.ietf.org/rfc/rfc1738.txt">URL</abbrev>'s
- and accessibility of referenced objects:</para>
+ <para>Do not forget to provide unit tests at least for the image
+ network accessibility part.</para>
- <programlisting language="java">package dom.xpath;
-...
-public class CheckUrl {
- public static void checkReadability(final String urlRef) {
- try {
- final URL url = new URL(urlRef);
- try {
- final Object imgCandidate = url.getContent();
- if (null == imgCandidate) {
- System.err.println("Unable to open '" + urlRef + "'");
- } else {
- System.out.println("Received '"
- + imgCandidate.getClass().getName() + "' from "
- + urlRef);
- }
- } catch (IOException e) {
- System.err.println("Unable to open '" + urlRef + "'");
- }
- } catch (MalformedURLException e) {
- System.err.println("Adress '" + urlRef + "' is malformed");
- }
- }
-}</programlisting>
+ <caution>
+ <para>Notice the response code for
+ <uri>http://www.hdm-stuttgart.de/rotfl.gif</uri>: This
+ resource is actually unavailable! But the web server tries to
+ recover by redirecting to an error page. Moreover a web server
+ may decide to return misleading response codes if deciding
+ your user agent is unable to handle the content type in
+ question. You may catch a glimpse of related problems by
+ reading <link
+ xlink:href="http://stackoverflow.com/questions/1378199/how-to-check-if-a-url-exists-or-returns-404-with-java">How
+ to check if a URL exists or returns 404 with Java?</link>. For
+ the current exercise we will not dig deeper into the
+ subject.</para>
+ </caution>
<tip>
<para>Using XPath expressions in conjunction with namespaces
@@ -1649,6 +1643,15 @@ public class CheckUrl {
xlink:href="http://www.jdom.org/pipermail/jdom-interest/2012-May/016850.html">XPath
examples</link></para>
</listitem>
+
+ <listitem>
+ <para>For analyzing the accessibility of referenced <xref
+ linkend="glo_HTTP"/> / <acronym>HTTPS</acronym> resources
+ see the previously mentioned discussion in <link
+ xlink:href="http://stackoverflow.com/questions/1378199/how-to-check-if-a-url-exists-or-returns-404-with-java">How
+ to check if a URL exists or returns 404 with
+ Java?</link>.</para>
+ </listitem>
</itemizedlist>
</tip>
</question>
@@ -1687,8 +1690,9 @@ public class CheckUrl {
<xref linkend="glo_XHTML"/> namespace. We thus create a
corresponding <classname
xlink:href="http://www.jdom.org/docs/apidocs/org/jdom2/Namespace.html">Namespace</classname>
- instance along with the desired <code>xhtml</code>
- prefix:</para>
+ instance handling the desired one to one correspondence between
+ the <code>"xhtml"</code> prefix and our target namespace
+ <uri>http://www.w3.org/1999/xhtml</uri>:</para>
<programlisting language="java">final Namespace htmlNamespace = // This will allow for XPath
Namespace.getNamespace("xhtml", // expressions like xhtml:img
diff --git a/P/Sda1/VerifyImgAccess/src/main/resources/fileextref.html b/P/Sda1/VerifyImgAccess/fileextref.html
similarity index 71%
rename from P/Sda1/VerifyImgAccess/src/main/resources/fileextref.html
rename to P/Sda1/VerifyImgAccess/fileextref.html
index 4f8fdaf3a..be22b98c7 100644
--- a/P/Sda1/VerifyImgAccess/src/main/resources/fileextref.html
+++ b/P/Sda1/VerifyImgAccess/fileextref.html
@@ -1,24 +1,18 @@
-<?xml version="1.0"?>
-<!--
-The pre- html-5 way:
-<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
- "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
- -->
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
-
<head>
<title>External Pictures</title>
</head>
<body>
<h1>External Pictures</h1>
<p>A local image reference:<img src="inline.gif" alt="none"/></p>
+ <p>What about ftp?<img src="ftp://inexistent.com/q.png" alt="none"/></p>
<table>
<tbody>
<tr>
<td>An existing picture:</td>
<td><img
- src="http://www.hdm-stuttgart.de/bilder_navigation/laptop.gif"
+ src="https://www.hdm-stuttgart.de/bilder_navigation/laptop.gif"
alt="none"/></td>
</tr>
<tr>
diff --git a/P/Sda1/VerifyImgAccess/pom.xml b/P/Sda1/VerifyImgAccess/pom.xml
index 9c943b7b9..b40fd8179 100644
--- a/P/Sda1/VerifyImgAccess/pom.xml
+++ b/P/Sda1/VerifyImgAccess/pom.xml
@@ -33,5 +33,13 @@
<version>${jaxen.jaxen.version}</version>
</dependency>
+ <!-- HTTP/HTTPS response codes -->
+ <dependency>
+ <groupId>javax</groupId>
+ <artifactId>javaee-api</artifactId>
+ <version>7.0</version>
+ </dependency>
+
+
</dependencies>
</project>
diff --git a/P/Sda1/VerifyImgAccess/src/main/java/dom/xpath/CheckExtImage.java b/P/Sda1/VerifyImgAccess/src/main/java/dom/xpath/CheckExtImage.java
index 8c5e98cf0..1367135c6 100644
--- a/P/Sda1/VerifyImgAccess/src/main/java/dom/xpath/CheckExtImage.java
+++ b/P/Sda1/VerifyImgAccess/src/main/java/dom/xpath/CheckExtImage.java
@@ -1,7 +1,6 @@
package dom.xpath;
import java.io.IOException;
-import java.util.List;
import org.jdom2.Document;
import org.jdom2.Element;
@@ -28,18 +27,21 @@ public class CheckExtImage {
public void process(final String xhtmlFilename) throws JDOMException, IOException {
final Document htmlInput = builder.build(xhtmlFilename);
-
+
final Namespace htmlNamespace = // This will allow for XPath expressions like xhtml:img
Namespace.getNamespace("xhtml", "http://www.w3.org/1999/xhtml");
-
+
final XPathExpression<Element> xpath = XPathFactory.instance().compile (
"//xhtml:img[starts-with(@src, 'http://') or starts-with(@src, 'https://') or starts-with(@src, 'ftp://')]",
new ElementFilter(), null, htmlNamespace);
-
- final List<Element> images = xpath.evaluate (htmlInput);
- for (final Element image: images) {
- CheckUrl.checkReadability(image.getAttributeValue("src"));
- }
+ xpath.evaluate(htmlInput).stream().
+ map(img -> img.getAttributeValue("src")).
+ forEach(CheckExtImage::printResult);
}
+
+ static private void printResult(String url) {
+ System.out.println(url
+ + ", HTTP Status: " + CheckUrl.checkReadability(url));
+ }
}
\ No newline at end of file
diff --git a/P/Sda1/VerifyImgAccess/src/main/java/dom/xpath/CheckExtImageDriver.java b/P/Sda1/VerifyImgAccess/src/main/java/dom/xpath/CheckExtImageDriver.java
index 5e7fc7a93..dc051be0b 100644
--- a/P/Sda1/VerifyImgAccess/src/main/java/dom/xpath/CheckExtImageDriver.java
+++ b/P/Sda1/VerifyImgAccess/src/main/java/dom/xpath/CheckExtImageDriver.java
@@ -12,6 +12,6 @@ public class CheckExtImageDriver {
*/
public static void main(String[] argv) throws Exception {
final CheckExtImage ao = new CheckExtImage();
- ao.process("src/main/resources/fileextref.html");
+ ao.process("fileextref.html");
}
}
\ No newline at end of file
diff --git a/P/Sda1/VerifyImgAccess/src/main/java/dom/xpath/CheckUrl.java b/P/Sda1/VerifyImgAccess/src/main/java/dom/xpath/CheckUrl.java
index 6fe0a4cc8..f82f1e3c6 100644
--- a/P/Sda1/VerifyImgAccess/src/main/java/dom/xpath/CheckUrl.java
+++ b/P/Sda1/VerifyImgAccess/src/main/java/dom/xpath/CheckUrl.java
@@ -1,9 +1,16 @@
package dom.xpath;
import java.io.IOException;
+import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
+import javax.ws.rs.core.Response;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+
/** Check Readability of a given URL
* @author $Author: goik $
* @version $Rev: 290 $ $Date: 2007-11-19 17:49:15 +0100 (Mo, 19. Nov 2007) $
@@ -12,28 +19,41 @@ import java.net.URL;
*
*/
public class CheckUrl {
+
+ static private final Logger log = LogManager.getLogger(CheckUrl.class);
+
/** Check whether a given object like http://someserver.com/img.gif
* can be retrieved.
+ *
* @param urlRef
* The URL to be checked for read access
+ *
+ * @return An informative URL related status message or null e.g. if the protocol in question is unknown.
*/
- public static void checkReadability(final String urlRef) {
+ public static Response.Status checkReadability(final String urlRef) {
try {
final URL url = new URL(urlRef);
- try {
- final Object imgCandidate = url.getContent();
- if (null == imgCandidate) {
- System.err.println("Unable to open '" + urlRef + "'");
- } else {
- System.out.println("Received '"
- + imgCandidate.getClass().getName() + "' from "
- + urlRef);
- }
- } catch (IOException e) {
- System.err.println("Unable to open '" + urlRef + "'");
+
+ switch(url.getProtocol()) {
+
+ case "http":
+ case "https":
+ try {
+ final HttpURLConnection huc = (HttpURLConnection) url.openConnection();
+ huc.setRequestMethod("GET");
+ huc.connect();
+ return Response.Status.fromStatusCode(huc.getResponseCode());
+ } catch (final IOException e) {
+ log.error("Unable to connect to " + urlRef, e);
+ }
+ break;
+ default:
+ log.error("Protocol '" + url.getProtocol() + "' not yet implemented");
}
+
} catch (MalformedURLException e) {
System.err.println("Adress '" + urlRef + "' is malformed");
}
+ return null;
}
}
\ No newline at end of file
diff --git a/P/Sda1/VerifyImgAccess/src/main/resources/log4j2.xml b/P/Sda1/VerifyImgAccess/src/main/resources/log4j2.xml
index 885670527..3cceed50d 100644
--- a/P/Sda1/VerifyImgAccess/src/main/resources/log4j2.xml
+++ b/P/Sda1/VerifyImgAccess/src/main/resources/log4j2.xml
@@ -11,10 +11,10 @@
<Loggers>
<!-- You my want to define class or package level per-logger rules -->
- <Logger name="de.hdm_stuttgart.mi.sda1.alignimg.App" level="warn">
+ <Logger name="de.hdm_stuttgart.mi.sda1.alignimg.App" level="debug">
<AppenderRef ref="A1"/>
</Logger>
- <Root level="warn">
+ <Root level="debug">
<AppenderRef ref="STDOUT"/>
</Root>
</Loggers>
diff --git a/P/Sda1/VerifyImgAccess/src/test/java/alignimg/TestImgSearch.java b/P/Sda1/VerifyImgAccess/src/test/java/alignimg/TestImgSearch.java
index f349eb2d9..03d2ecb1d 100644
--- a/P/Sda1/VerifyImgAccess/src/test/java/alignimg/TestImgSearch.java
+++ b/P/Sda1/VerifyImgAccess/src/test/java/alignimg/TestImgSearch.java
@@ -1,18 +1,31 @@
package alignimg;
-import java.io.IOException;
-
-import javax.xml.parsers.ParserConfigurationException;
+import javax.ws.rs.core.Response;
+import org.junit.Assert;
import org.junit.Test;
-import org.xml.sax.SAXException;
+import dom.xpath.CheckUrl;
+
+/**
+ *
+ */
public class TestImgSearch {
+ /**
+ */
@Test
- public void searchAlignImageElements() throws ParserConfigurationException,
- SAXException, IOException {
-
-
+ public void findExistingImage() {
+ Assert.assertTrue(Response.Status.OK ==
+ CheckUrl.checkReadability(
+ "https://www.hdm-stuttgart.de/bilder_navigation/laptop.gif"));
+ }
+ /**
+ */
+ @Test
+ public void findRedirectErrorPage() {
+ Assert.assertTrue(Response.Status.FOUND ==
+ CheckUrl.checkReadability(
+ "http://www.hdm-stuttgart.de/rotfl.gif"));
}
}
\ No newline at end of file
--
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