Adds RDF/XML server output and upgrades quick_xml

lib/Cargo.toml

@@ -20,7 +20,7 @@ lazy_static = "1"
 rocksdb = { version = "0.12", optional = true }
 uuid = { version = "0.7", features = ["v4"] }
 byteorder = { version = "1", features = ["i128"] }
-quick-xml = "0.15"
+quick-xml = { version = "0.16", features = ["failure"] }
 ordered-float = "1"
 num-traits = "0.2"
 rust_decimal = "1"

lib/src/sparql/json_results.rs

@@ -53,7 +53,7 @@ pub fn write_json_results<W: Write>(results: QueryResult<'_>, mut sink: W) -> Re
                             }
                             Term::BlankNode(bnode) => {
                                 sink.write_all(b":{\"type\":\"bnode\",\"value\":")?;
-                                sink.write_fmt(format_args!("{}", bnode.as_uuid().to_simple()))?;
+                                write!(sink, "{}", bnode.as_uuid().to_simple())?;
                                 sink.write_all(b"}")?;
                             }
                             Term::Literal(literal) => {
@@ -113,7 +113,7 @@ fn write_escaped_json_string(s: &str, sink: &mut impl Write) -> Result<()> {
                         }
                     }
                 } else {
-                    sink.write_fmt(format_args!("{}", c))
+                    write!(sink, "{}", c)
                 }
             }
         }?;

lib/src/sparql/model.rs

@@ -1,8 +1,10 @@
 use crate::model::*;
 use crate::sparql::json_results::write_json_results;
 use crate::sparql::xml_results::{read_xml_results, write_xml_results};
-use crate::{FileSyntax, Result};
+use crate::{FileSyntax, GraphSyntax, Result};
 use failure::format_err;
+use quick_xml::events::*;
+use quick_xml::Writer;
 use std::fmt;
 use std::io::{BufRead, Write};
 use uuid::Uuid;
@@ -31,6 +33,97 @@ impl<'a> QueryResult<'a> {
             QueryResultSyntax::Json => write_json_results(self, writer),
         }
     }
+
+    pub fn write_graph<W: Write>(self, mut writer: W, syntax: GraphSyntax) -> Result<W> {
+        if let QueryResult::Graph(triples) = self {
+            match syntax {
+                GraphSyntax::NTriples | GraphSyntax::Turtle => {
+                    for triple in triples {
+                        writeln!(&mut writer, "{}", triple?)?
+                    }
+                    Ok(writer)
+                }
+                GraphSyntax::RdfXml => {
+                    let mut writer = Writer::new(writer);
+                    writer.write_event(Event::Decl(BytesDecl::new(b"1.0", None, None)))?;
+                    let mut rdf_open = BytesStart::borrowed_name(b"rdf:RDF");
+                    rdf_open.push_attribute((
+                        "xmlns:rdf",
+                        "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
+                    ));
+                    writer.write_event(Event::Start(rdf_open))?;
+
+                    let mut current_subject = None;
+                    for triple in triples {
+                        let triple = triple?;
+
+                        // We open a new rdf:Description if useful
+                        if current_subject.as_ref() != Some(triple.subject()) {
+                            if current_subject.is_some() {
+                                writer.write_event(Event::End(BytesEnd::borrowed(
+                                    b"rdf:Description",
+                                )))?;
+                            }
+
+                            let mut description_open =
+                                BytesStart::borrowed_name(b"rdf:Description");
+                            match triple.subject() {
+                                NamedOrBlankNode::NamedNode(n) => {
+                                    description_open.push_attribute(("rdf:about", n.as_str()))
+                                }
+                                NamedOrBlankNode::BlankNode(n) => {
+                                    let id = n.as_uuid().to_simple().to_string();
+                                    description_open.push_attribute(("rdf:nodeID", id.as_str()))
+                                }
+                            }
+                            writer.write_event(Event::Start(description_open))?;
+                        }
+
+                        let mut property_open = BytesStart::borrowed_name(b"prop:");
+                        let mut content = None;
+                        property_open.push_attribute(("xmlns:prop", triple.predicate().as_str()));
+                        match triple.object() {
+                            Term::NamedNode(n) => {
+                                property_open.push_attribute(("rdf:resource", n.as_str()))
+                            }
+                            Term::BlankNode(n) => {
+                                let id = n.as_uuid().to_simple().to_string();
+                                property_open.push_attribute(("rdf:nodeID", id.as_str()))
+                            }
+                            Term::Literal(l) => {
+                                if let Some(language) = l.language() {
+                                    property_open.push_attribute(("xml:lang", language.as_str()))
+                                } else if !l.is_plain() {
+                                    property_open
+                                        .push_attribute(("rdf:datatype", l.datatype().as_str()))
+                                }
+                                content = Some(l.value());
+                            }
+                        }
+                        if let Some(content) = content {
+                            writer.write_event(Event::Start(property_open))?;
+                            writer.write_event(Event::Text(BytesText::from_plain_str(&content)))?;
+                            writer.write_event(Event::End(BytesEnd::borrowed(b"prop:")))?;
+                        } else {
+                            writer.write_event(Event::Empty(property_open))?;
+                        }
+
+                        current_subject = Some(triple.subject_owned());
+                    }
+
+                    if current_subject.is_some() {
+                        writer.write_event(Event::End(BytesEnd::borrowed(b"rdf:Description")))?;
+                    }
+                    writer.write_event(Event::End(BytesEnd::borrowed(b"rdf:RDF")))?;
+                    Ok(writer.into_inner())
+                }
+            }
+        } else {
+            Err(format_err!(
+                "Bindings or booleans could not be formatted as an RDF graph"
+            ))
+        }
+    }
 }
 
 /// [SPARQL query](https://www.w3.org/TR/sparql11-query/) serialization formats

lib/src/sparql/xml_results.rs

@@ -132,7 +132,7 @@ pub fn read_xml_results<'a>(source: impl BufRead + 'a) -> Result<QueryResult<'a>
                 if ns != b"http://www.w3.org/2005/sparql-results#".as_ref() {
                     return Err(format_err!(
                         "Unexpected namespace found in RDF/XML query result: {}",
-                        reader.decode(ns)
+                        reader.decode(ns)?
                     ));
                 }
             }
@@ -144,20 +144,20 @@ pub fn read_xml_results<'a>(source: impl BufRead + 'a) -> Result<QueryResult<'a>
                     if event.name() == b"sparql" {
                         state = State::Sparql;
                     } else {
-                        return Err(format_err!("Expecting <sparql> tag, found {}", reader.decode(event.name())));
+                        return Err(format_err!("Expecting <sparql> tag, found {}", reader.decode(event.name())?));
                     }
                 }
                 State::Sparql => {
                     if event.name() == b"head" {
                         state = State::Head;
                     } else {
-                        return Err(format_err!("Expecting <head> tag, found {}", reader.decode(event.name())));
+                        return Err(format_err!("Expecting <head> tag, found {}", reader.decode(event.name())?));
                     }
                 }
                 State::Head => if event.name() == b"variable" || event.name() == b"link" {
                     return Err(format_err!("<variable> and <link> tag should be autoclosing"));
                 } else {
-                    return Err(format_err!("Expecting <variable> or <link> tag, found {}", reader.decode(event.name())));
+                    return Err(format_err!("Expecting <variable> or <link> tag, found {}", reader.decode(event.name())?));
                 }
                 State::AfterHead => {
                     if event.name() == b"boolean" {
@@ -178,10 +178,10 @@ pub fn read_xml_results<'a>(source: impl BufRead + 'a) -> Result<QueryResult<'a>
                             }),
                         )));
                     } else if event.name() != b"link" && event.name() != b"results" && event.name() != b"boolean" {
-                        return Err(format_err!("Expecting sparql tag, found {}", reader.decode(event.name())));
+                        return Err(format_err!("Expecting sparql tag, found {}", reader.decode(event.name())?));
                     }
                 }
-                State::Boolean => return Err(format_err!("Unexpected tag inside of <boolean> tag: {}", reader.decode(event.name())))
+                State::Boolean => return Err(format_err!("Unexpected tag inside of <boolean> tag: {}", reader.decode(event.name())?))
             },
             Event::Empty(event) => match state {
                 State::Head => {
@@ -194,7 +194,7 @@ pub fn read_xml_results<'a>(source: impl BufRead + 'a) -> Result<QueryResult<'a>
                     } else if event.name() == b"link" {
                         // no op
                     } else {
-                        return Err(format_err!("Expecting <variable> or <link> tag, found {}", reader.decode(event.name())));
+                        return Err(format_err!("Expecting <variable> or <link> tag, found {}", reader.decode(event.name())?));
                     }
                 },
                 State::AfterHead => {
@@ -204,10 +204,10 @@ pub fn read_xml_results<'a>(source: impl BufRead + 'a) -> Result<QueryResult<'a>
                             Box::new(empty()),
                         )))
                     } else {
-                        return Err(format_err!("Unexpected autoclosing tag <{}>", reader.decode(event.name())))
+                        return Err(format_err!("Unexpected autoclosing tag <{}>", reader.decode(event.name())?))
                     }
                 }
-                _ => return Err(format_err!("Unexpected autoclosing tag <{}>", reader.decode(event.name())))
+                _ => return Err(format_err!("Unexpected autoclosing tag <{}>", reader.decode(event.name())?))
             },
             Event::Text(event) => {
                 let value = event.unescaped()?;
@@ -218,10 +218,10 @@ pub fn read_xml_results<'a>(source: impl BufRead + 'a) -> Result<QueryResult<'a>
                         } else if value.as_ref() == b"false" {
                             Ok(QueryResult::Boolean(false))
                         } else {
-                            Err(format_err!("Unexpected boolean value. Found {}", reader.decode(&value)))
+                            Err(format_err!("Unexpected boolean value. Found {}", reader.decode(&value)?))
                         };
                     }
-                    _ => Err(format_err!("Unexpected textual value found: {}", reader.decode(&value)))
+                    _ => Err(format_err!("Unexpected textual value found: {}", reader.decode(&value)?))
                 };
             },
             Event::End(_) => if let State::Head = state {
@@ -247,6 +247,12 @@ impl<R: BufRead> Iterator for ResultsIterator<R> {
     type Item = Result<Vec<Option<Term>>>;
 
     fn next(&mut self) -> Option<Result<Vec<Option<Term>>>> {
+        self.read_next().transpose()
+    }
+}
+
+impl<R: BufRead> ResultsIterator<R> {
+    fn read_next(&mut self) -> Result<Option<Vec<Option<Term>>>> {
         enum State {
             Start,
             Result,
@@ -266,19 +272,15 @@ impl<R: BufRead> Iterator for ResultsIterator<R> {
         let mut lang = None;
         let mut datatype = None;
         loop {
-            let (ns, event) = match self
+            let (ns, event) = self
                 .reader
-                .read_namespaced_event(&mut self.buffer, &mut self.namespace_buffer)
+                .read_namespaced_event(&mut self.buffer, &mut self.namespace_buffer)?;
-            {
-                Ok(v) => v,
-                Err(error) => return Some(Err(error.into())),
-            };
             if let Some(ns) = ns {
                 if ns != b"http://www.w3.org/2005/sparql-results#".as_ref() {
-                    return Some(Err(format_err!(
+                    return Err(format_err!(
                         "Unexpected namespace found in RDF/XML query result: {}",
-                        self.reader.decode(ns)
+                        self.reader.decode(ns)?
-                    )));
+                    ));
                 }
             }
             match event {
@@ -287,10 +289,10 @@ impl<R: BufRead> Iterator for ResultsIterator<R> {
                         if event.name() == b"result" {
                             state = State::Result;
                         } else {
-                            return Some(Err(format_err!(
+                            return Err(format_err!(
                                 "Expecting <result>, found {}",
-                                self.reader.decode(event.name())
+                                self.reader.decode(event.name())?
-                            )));
+                            ));
                         }
                     }
                     State::Result => {
@@ -300,29 +302,26 @@ impl<R: BufRead> Iterator for ResultsIterator<R> {
                                 .filter_map(|attr| attr.ok())
                                 .find(|attr| attr.key == b"name")
                             {
-                                Some(attr) => match attr.unescaped_value() {
+                                Some(attr) => current_var = Some(attr.unescaped_value()?.to_vec()),
-                                    Ok(var) => current_var = Some(var.to_vec()),
-                                    Err(error) => return Some(Err(error.into())),
-                                },
                                 None => {
-                                    return Some(Err(format_err!(
+                                    return Err(format_err!(
                                         "No name attribute found for the <binding> tag"
-                                    )));
+                                    ));
                                 }
                             }
                             state = State::Binding;
                         } else {
-                            return Some(Err(format_err!(
+                            return Err(format_err!(
                                 "Expecting <binding>, found {}",
-                                self.reader.decode(event.name())
+                                self.reader.decode(event.name())?
-                            )));
+                            ));
                         }
                     }
                     State::Binding => {
                         if term.is_some() {
-                            return Some(Err(format_err!(
+                            return Err(format_err!(
                                 "There is already a value for the current binding"
-                            )));
+                            ));
                         }
                         if event.name() == b"uri" {
                             state = State::Uri;
@@ -332,43 +331,30 @@ impl<R: BufRead> Iterator for ResultsIterator<R> {
                             for attr in event.attributes() {
                                 if let Ok(attr) = attr {
                                     if attr.key == b"xml:lang" {
-                                        match attr.unescape_and_decode_value(&self.reader) {
+                                        lang = Some(attr.unescape_and_decode_value(&self.reader)?);
-                                            Ok(val) => lang = Some(val),
-                                            Err(error) => return Some(Err(error.into())),
-                                        }
                                     } else if attr.key == b"datatype" {
-                                        match attr.unescaped_value() {
+                                        datatype = Some(NamedNode::parse(
-                                            Ok(val) => {
+                                            attr.unescape_and_decode_value(&self.reader)?,
-                                                match NamedNode::parse(
+                                        )?);
-                                                    self.reader.decode(&val).to_string(),
-                                                ) {
-                                                    Ok(iri) => datatype = Some(iri),
-                                                    Err(error) => return Some(Err(error)),
-                                                }
-                                            }
-                                            Err(error) => return Some(Err(error.into())),
-                                        }
                                     }
                                 }
                             }
                             state = State::Literal;
                         } else {
-                            return Some(Err(format_err!(
+                            return Err(format_err!(
                                 "Expecting <uri>, <bnode> or <literal> found {}",
-                                self.reader.decode(event.name())
+                                self.reader.decode(event.name())?
-                            )));
+                            ));
                         }
                     }
                     _ => (),
                 },
-                Event::Text(event) => match event.unescaped() {
+                Event::Text(event) => {
-                    Ok(data) => match state {
+                    let data = event.unescaped()?;
-                        State::Uri => match NamedNode::parse(self.reader.decode(&data)) {
+                    match state {
-                            Ok(uri) => {
+                        State::Uri => {
-                                term = Some(uri.into());
+                            term = Some(NamedNode::parse(self.reader.decode(&data)?)?.into())
                         }
-                            Err(error) => return Some(Err(error)),
-                        },
                         State::BNode => {
                             term = Some(
                                 self.bnodes_map
@@ -379,33 +365,33 @@ impl<R: BufRead> Iterator for ResultsIterator<R> {
                             )
                         }
                         State::Literal => {
-                            let value = self.reader.decode(&data).to_string();
+                            term = Some(
-                            term = Some(build_literal(value, &lang, &datatype).into());
+                                build_literal(self.reader.decode(&data)?, &lang, &datatype).into(),
+                            );
                         }
                         _ => {
-                            return Some(Err(format_err!(
+                            return Err(format_err!(
                                 "Unexpected textual value found: {}",
-                                self.reader.decode(&data)
+                                self.reader.decode(&data)?
-                            )));
+                            ));
+                        }
+                    }
                 }
-                    },
-                    Err(error) => return Some(Err(error.into())),
-                },
                 Event::End(_) => match state {
                     State::Start => state = State::End,
-                    State::Result => return Some(Ok(new_bindings)),
+                    State::Result => return Ok(Some(new_bindings)),
                     State::Binding => {
                         match (&current_var, &term) {
                             (Some(var), Some(term)) => {
                                 new_bindings[self.mapping[var]] = Some(term.clone())
                             }
                             (Some(var), None) => {
-                                return Some(Err(format_err!(
+                                return Err(format_err!(
                                     "No variable found for variable {}",
-                                    self.reader.decode(&var)
+                                    self.reader.decode(&var)?
-                                )));
+                                ));
                             }
-                            _ => return Some(Err(format_err!("No name found for <binding> tag"))),
+                            _ => return Err(format_err!("No name found for <binding> tag")),
                         }
                         term = None;
                         state = State::Result;
@@ -420,7 +406,7 @@ impl<R: BufRead> Iterator for ResultsIterator<R> {
                     }
                     _ => (),
                 },
-                Event::Eof => return None,
+                Event::Eof => return Ok(None),
                 _ => (),
             }
         }

server/src/main.rs

@@ -10,7 +10,6 @@ use rudf::{
     DatasetSyntax, FileSyntax, GraphSyntax, MemoryRepository, Repository, RepositoryConnection,
     RocksDbRepository,
 };
-use std::fmt::Write;
 use std::io::{BufReader, Read};
 use std::sync::Arc;
 
@@ -143,11 +142,13 @@ fn evaluate_sparql_query<R: RepositoryConnection>(
 ) -> Response {
     //TODO: stream
     match connection.prepare_query(query, None) {
-        Ok(query) => match query.exec().unwrap() {
+        Ok(query) => {
-            QueryResult::Graph(triples) => {
+            let results = query.exec().unwrap();
+            if let QueryResult::Graph(_) = results {
                 let supported_formats = [
                     GraphSyntax::NTriples.media_type(),
                     GraphSyntax::Turtle.media_type(),
+                    GraphSyntax::RdfXml.media_type(),
                 ];
                 let format = if let Some(accept) = request.header("Accept") {
                     if let Some(media_type) =
@@ -165,13 +166,12 @@ fn evaluate_sparql_query<R: RepositoryConnection>(
                 } else {
                     GraphSyntax::NTriples
                 };
-                let mut result = String::default();
+
-                for triple in triples {
+                Response::from_data(
-                    writeln!(&mut result, "{}", triple.unwrap()).unwrap()
+                    format.media_type(),
-                }
+                    results.write_graph(Vec::default(), format).unwrap(),
-                Response::from_data(format.media_type(), result.into_bytes())
+                )
-            }
+            } else {
-            result => {
                 let supported_formats = [
                     QueryResultSyntax::Xml.media_type(),
                     QueryResultSyntax::Json.media_type(),
@@ -190,15 +190,15 @@ fn evaluate_sparql_query<R: RepositoryConnection>(
                         .with_status_code(415);
                     }
                 } else {
-                    QueryResultSyntax::Xml
+                    QueryResultSyntax::Json
                 };
 
                 Response::from_data(
                     format.media_type(),
-                    result.write(Vec::default(), format).unwrap(),
+                    results.write(Vec::default(), format).unwrap(),
                 )
             }
-        },
+        }
         Err(error) => Response::text(error.to_string()).with_status_code(400),
     }
 }