public void endDocument() {
                metadata.set("language", getLanguage().getLanguage());
            }
Get a specific metadata field. If the input stream cannot be parsed, but a
value was found for the given metadata field, then the value of the field
is returned as part of a 200 OK response; otherwise a
{@link javax.ws.rs.core.Response.Status#BAD_REQUEST} is generated. If the stream
was successfully parsed but the specific metadata field was not found, then a
{@link javax.ws.rs.core.Response.Status#NOT_FOUND} is returned.
<p/>
Note that this method handles multivalue fields and returns possibly more
metadata value than requested.
<p/>
If you want XMP, you must be careful to specify the exact XMP key.
For example, "Author" will return nothing, but "dc:creator" will return the correct value.

@param is          inputstream
@param httpHeaders httpheaders
@param info        info
@param field       the tika metadata field name
@return one of {@link javax.ws.rs.core.Response.Status#OK},
{@link javax.ws.rs.core.Response.Status#NOT_FOUND}, or
{@link javax.ws.rs.core.Response.Status#BAD_REQUEST}
@throws Exception
tika-server/tika-server-core/src/main/java/org/apache/tika/server/core/resource/MetadataResource.java