add ISSN collector by record identifier

src/test/java/org/xbib/marc/filter/MarcFieldFilterByRecordIdentifierTest.java

@@ -0,0 +1,106 @@
+package org.xbib.marc.filter;
+
+import org.junit.Test;
+import org.xbib.content.XContentBuilder;
+import org.xbib.marc.Marc;
+import org.xbib.marc.MarcField;
+import org.xbib.marc.MarcFieldAdapter;
+import org.xbib.marc.MarcListener;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import java.util.stream.Collectors;
+
+import static org.xbib.content.json.JsonXContent.contentBuilder;
+
+/**
+ * Demo of collecting ISSNs by record identifier from a MARC file.
+ *
+ * "issns.mrc" courtesy of Steven Hirren (steven.hirren.gmail.com)
+ */
+public class MarcFieldFilterByRecordIdentifierTest {
+
+    private static final Logger logger = Logger.getLogger(MarcFieldFilterByRecordIdentifierTest.class.getName());
+
+    @Test
+    public void findISSNs() throws IOException {
+        Map<String, Map<String, List<Map<String, String>>>> result = new TreeMap<>();
+        // set up MARC listener
+        MarcListener marcListener = new MarcFieldAdapter() {
+            String recordIdentifier;
+            Map<String, List<Map<String, String>>> fields;
+            @Override
+            public void field(MarcField field) {
+                if ("001".equals(field.getTag())) {
+                    recordIdentifier = field.getValue();
+                    fields = new TreeMap<>();
+                }
+                Collection<Map<String, String>> values = field.getSubfields().stream()
+                        .filter(f -> matchISSNField(field, f))
+                        .map(f -> Collections.singletonMap(f.getId(), f.getValue()))
+                        .collect(Collectors.toList());
+                if (!values.isEmpty()) {
+                    fields.putIfAbsent(field.getTag(), new ArrayList<>());
+                    List<Map<String, String>> list = fields.get(field.getTag());
+                    list.addAll(values);
+                    fields.put(field.getTag(), list);
+                }
+            }
+            @Override
+            public void endRecord() {
+                result.put(recordIdentifier, fields);
+            }
+        };
+        // read MARC file
+        Marc.builder()
+                .setInputStream(getClass().getResource("issns.mrc").openStream())
+                .setMarcListener(marcListener)
+                .build()
+                .writeCollection();
+
+        // collect all ISSNs from all records and all fields and make them unique
+        List<? super Map<String, String>> issns =
+                result.values().stream()
+                .map(Map::values)
+                .flatMap(Collection::stream)
+                .collect(Collectors.toList()).stream()
+                .flatMap(Collection::stream)
+                .collect(Collectors.toList()).stream()
+                .map(Map::values)
+                .flatMap(Collection::stream)
+                .distinct()
+                .collect(Collectors.toList());
+
+        // JSON output
+        XContentBuilder builder = contentBuilder().prettyPrint()
+                .startObject();
+        for (Map.Entry<String, Map<String, List<Map<String, String>>>> entry : result.entrySet()) {
+            builder.field(entry.getKey(), entry.getValue());
+        }
+        builder.field("issns", issns);
+        builder.endObject();
+
+        logger.log(Level.INFO, builder.string());
+    }
+
+    private static boolean matchISSNField(MarcField field, MarcField.Subfield subfield) {
+        switch (field.getTag()) {
+            case "011": {
+                return "a".equals(subfield.getId()) || "f".equals(subfield.getId());
+            }
+            case "421":
+            case "451":
+            case "452":
+            case "488":
+                return "x".equals(subfield.getId());
+        }
+        return false;
+    }
+}