TIKA-4759 - use a markdown writer (#2900)

Author: tballison

tika-app/src/main/appended-resources/META-INF/LICENSE

@@ -900,3 +900,32 @@ Sqlite (included in the "provided" org.xerial's sqlite-jdbc)
     Sqlite is in the Public Domain.  For details
     see: https://www.sqlite.org/copyright.html
 
+commonmark-java libraries (commonmark, commonmark-ext-gfm-tables, and
+commonmark-ext-gfm-strikethrough)
+
+    The BSD 2-Clause License
+
+    Copyright (c) 2015, Atlassian Pty Ltd
+    All rights reserved.
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright notice, this
+      list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above copyright notice,
+      this list of conditions and the following disclaimer in the documentation
+      and/or other materials provided with the distribution.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+    FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+    DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+    SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+    OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+

tika-bundles/tika-bundle-standard/src/test/java/org/apache/tika/bundle/BundleIT.java

@@ -85,12 +85,19 @@ static void startFramework() throws Exception {
         // Install all bundles first, then start.
         // tika-core requires osgi.serviceloader capabilities that are
         // provided by tika-bundle-standard, so both must be installed
-        // before either can resolve.
+        // before either can resolve. tika-core also imports the org.commonmark
+        // packages (Markdown serialization), so those bundles must be present too.
         Bundle commonsIo = install("commons-io.jar");
+        Bundle commonmark = install("commonmark.jar");
+        Bundle commonmarkTables = install("commonmark-ext-gfm-tables.jar");
+        Bundle commonmarkStrikethrough = install("commonmark-ext-gfm-strikethrough.jar");
         Bundle tikaCore = install("tika-core.jar");
         Bundle tikaBundle = install("tika-bundle-standard.jar");
 
         commonsIo.start();
+        commonmark.start();
+        commonmarkTables.start();
+        commonmarkStrikethrough.start();
         tikaCore.start();
         tikaBundle.start();
     }

tika-bundles/tika-bundle-standard/test-bundles.xml

@@ -30,6 +30,9 @@
         <include>org.apache.tika:tika-core</include>
         <include>org.apache.tika:tika-bundle-standard</include>
         <include>commons-io:commons-io</include>
+        <include>org.commonmark:commonmark</include>
+        <include>org.commonmark:commonmark-ext-gfm-tables</include>
+        <include>org.commonmark:commonmark-ext-gfm-strikethrough</include>
       </includes>
     </dependencySet>
     <dependencySet>

tika-core/pom.xml

@@ -44,6 +44,20 @@
       <groupId>commons-io</groupId>
       <artifactId>commons-io</artifactId>
     </dependency>
+    <!-- Markdown serialization (ToMarkdownContentHandler). BSD 2-Clause, ASF Category A,
+         zero transitive dependencies. -->
+    <dependency>
+      <groupId>org.commonmark</groupId>
+      <artifactId>commonmark</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.commonmark</groupId>
+      <artifactId>commonmark-ext-gfm-tables</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.commonmark</groupId>
+      <artifactId>commonmark-ext-gfm-strikethrough</artifactId>
+    </dependency>
 
     <!-- Optional OSGi dependencies, used only when running within OSGi -->
     <dependency>