svn commit: r1485971 - /clerezza/trunk/jaxrs.rdf.providers/src/main/java/org/apache/clerezza/jaxrs/sparql/providers/ResultSetCsvMessageBodyWriter.java

[mi...@apache.org]

Author: misl
Date: Fri May 24 08:31:31 2013
New Revision: 1485971

URL: http://svn.apache.org/r1485971
Log:
CLEREZZA-785: Added ResultSetCsvMessageBodyProvider to support CSV output.

Added:
    clerezza/trunk/jaxrs.rdf.providers/src/main/java/org/apache/clerezza/jaxrs/sparql/providers/ResultSetCsvMessageBodyWriter.java

Added: clerezza/trunk/jaxrs.rdf.providers/src/main/java/org/apache/clerezza/jaxrs/sparql/providers/ResultSetCsvMessageBodyWriter.java
URL: http://svn.apache.org/viewvc/clerezza/trunk/jaxrs.rdf.providers/src/main/java/org/apache/clerezza/jaxrs/sparql/providers/ResultSetCsvMessageBodyWriter.java?rev=1485971&view=auto
==============================================================================
--- clerezza/trunk/jaxrs.rdf.providers/src/main/java/org/apache/clerezza/jaxrs/sparql/providers/ResultSetCsvMessageBodyWriter.java (added)
+++ clerezza/trunk/jaxrs.rdf.providers/src/main/java/org/apache/clerezza/jaxrs/sparql/providers/ResultSetCsvMessageBodyWriter.java Fri May 24 08:31:31 2013
@@ -0,0 +1,191 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.clerezza.jaxrs.sparql.providers;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.UnsupportedEncodingException;
+import java.lang.annotation.Annotation;
+import java.lang.reflect.Type;
+import java.util.List;
+
+import javax.ws.rs.Produces;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.MultivaluedMap;
+import javax.ws.rs.ext.MessageBodyWriter;
+import javax.ws.rs.ext.Provider;
+
+import org.apache.clerezza.rdf.core.BNode;
+import org.apache.clerezza.rdf.core.PlainLiteral;
+import org.apache.clerezza.rdf.core.Resource;
+import org.apache.clerezza.rdf.core.TypedLiteral;
+import org.apache.clerezza.rdf.core.UriRef;
+import org.apache.clerezza.rdf.core.sparql.ResultSet;
+import org.apache.clerezza.rdf.core.sparql.SolutionMapping;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Property;
+import org.apache.felix.scr.annotations.Service;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * MessageBodyWirter for <code>ResultSet</code>. Resulting output is csv and
+ * conforms to:
+ * http://www.w3.org/TR/2013/REC-sparql11-results-csv-tsv-20130321/#csv
+ * 
+ * Also see: http://tools.ietf.org/html/rfc4180
+ * 
+ * @author misl
+ */
+@Component
+@Service( Object.class )
+@Property( name = "javax.ws.rs", boolValue = true )
+@Produces( { "text/csv" } )
+@Provider
+public class ResultSetCsvMessageBodyWriter implements MessageBodyWriter<ResultSet> {
+
+  private static final Logger logger = LoggerFactory
+      .getLogger( ResultSetCsvMessageBodyWriter.class );
+  private static final String UTF_8 = "UTF-8";
+  private static byte[] separator;
+
+  static {
+    try {
+      separator = ",".getBytes( UTF_8 );
+    } catch( UnsupportedEncodingException e ) {
+      logger.error( "Developer error", e );
+    }
+
+  }
+
+  @Override
+  public boolean isWriteable( Class<?> type, Type genericType, Annotation[] annotations,
+      MediaType mediaType ) {
+    return ResultSet.class.isAssignableFrom( type );
+  }
+
+  @Override
+  public long getSize( ResultSet t, Class<?> type, Type genericType, Annotation[] annotations,
+      MediaType mediaType ) {
+    return -1;
+  }
+
+  @Override
+  public void writeTo( ResultSet resultSet, Class<?> type, Type genericType,
+      Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, Object> httpHeaders,
+      OutputStream entityStream ) throws IOException, WebApplicationException {
+
+    // According to spec header is mandatory.
+    writeCsvHeader( entityStream, resultSet.getResultVars() );
+    while( resultSet.hasNext() ) {
+      writeCsvLine( entityStream, resultSet.getResultVars(), resultSet.next() );
+    }
+  }
+
+  /**
+   * Write resultset header to the given output stream.
+   * 
+   * @param outputStream
+   *          stream to write to.
+   * @param headers
+   *          the headers to write.
+   * @throws IOException
+   */
+  private void writeCsvHeader( OutputStream outputStream, List<String> headers ) throws IOException {
+    boolean first = true;
+    for( String header : headers ) {
+      if( !first ) {
+        outputStream.write( separator );
+      }
+      writeEscaped( outputStream, header );
+      first = false;
+    }
+    outputStream.write( "\n".getBytes( UTF_8 ) );
+  }
+
+  /**
+   * Write a single csv line using the given line data.
+   * 
+   * @param outputStream
+   *          stream to write to.
+   * @param headers
+   *          the headers to write line data for.
+   * @param lineData
+   *          the line data to write.
+   * @throws IOException
+   */
+  private void writeCsvLine( OutputStream outputStream, List<String> headers,
+      SolutionMapping lineData ) throws IOException {
+    boolean first = true;
+    for( String header : headers ) {
+      if( !first ) {
+        outputStream.write( separator );
+      }
+      Resource resource = lineData.get( header );
+      if( resource != null ) {
+        writeEscaped( outputStream, getResourceValue( resource ) );
+      }
+      first = false;
+    }
+    outputStream.write( "\n".getBytes( UTF_8 ) );
+  }
+
+  /**
+   * Helper to get the proper string representation for the given Resource.
+   */
+  private String getResourceValue( Resource resource ) {
+    StringBuilder value = new StringBuilder();
+    if( resource instanceof UriRef ) {
+      value.append( ((UriRef) resource).getUnicodeString() );
+    } else if( resource instanceof TypedLiteral ) {
+      value.append( ((TypedLiteral) resource).getLexicalForm() );
+    } else if( resource instanceof PlainLiteral ) {
+      value.append( ((PlainLiteral) resource).getLexicalForm() );
+    } else if( resource instanceof BNode ) {
+      value.append( "/" );
+    } else {
+      value.append( resource.toString() );
+    }
+    return value.toString();
+  }
+
+  /**
+   * Write the given string to the output stream and escape the output where
+   * necessary.
+   * 
+   * @param outputStream
+   *          stream to write to.
+   * @param text
+   *          the text to write.
+   * @throws IOException
+   */
+  private void writeEscaped( OutputStream outputStream, String text ) throws IOException {
+    String line = text;
+    if( text.contains( "\r" ) || text.contains( "\n" ) || text.contains( "," )
+        || text.contains( "\"" ) ) {
+      StringBuilder builder = new StringBuilder();
+      builder.append( '"' );
+      builder.append( text.replaceAll( "\"", "\"\"" ) );
+      builder.append( '"' );
+      line = builder.toString();
+    }
+    outputStream.write( line.getBytes( UTF_8 ) );
+  }
+}