implemeted the one to many relationship for the metadata table using he

@ElementCollection annotation

src/main/java/uk/ac/ebi/eva/evaseqcol/controller/seqcol/SeqColController.java

@@ -83,6 +83,13 @@ public ResponseEntity<?> getSeqColByDigestAndLevel(
         return new ResponseEntity<>(HttpStatus.NOT_FOUND);
     }
 
+    @GetMapping(value = "/collection/{digest}/metadata")
+    public ResponseEntity<?> getSeqColByDigestAndLevelMetadata(@PathVariable String digest) {
+        return new ResponseEntity<>(
+                seqColService.getSeqColMetadataBySeqColDigest(digest), HttpStatus.OK
+        );
+    }
+
     @GetMapping("/service-info")
     public ResponseEntity<?> getServiceInfo() {
         try {

src/main/java/uk/ac/ebi/eva/evaseqcol/entities/SeqColEntity.java

@@ -17,8 +17,6 @@ public abstract class SeqColEntity {
 
     protected String digest; // The level 0 digest
 
-    protected NamingConvention namingConvention;
-
 
     public enum NamingConvention {
         ENA, GENBANK, UCSC, TEST

src/main/java/uk/ac/ebi/eva/evaseqcol/entities/SeqColLevelOneEntity.java

@@ -7,20 +7,21 @@
 import uk.ac.ebi.eva.evaseqcol.utils.JSONLevelOne;
 
 import javax.persistence.Basic;
+import javax.persistence.CollectionTable;
 import javax.persistence.Column;
+import javax.persistence.ElementCollection;
 import javax.persistence.Entity;
-import javax.persistence.EnumType;
-import javax.persistence.Enumerated;
 import javax.persistence.FetchType;
 import javax.persistence.Id;
-import javax.persistence.IdClass;
+import javax.persistence.JoinColumn;
 import javax.persistence.Table;
+import java.util.HashSet;
+import java.util.Set;
 
 @Entity
 @NoArgsConstructor
 @Data
 @Table(name = "sequence_collections_L1")
-@IdClass(SeqColId.class)
 public class SeqColLevelOneEntity extends SeqColEntity{
 
     @Id
@@ -32,15 +33,19 @@ public class SeqColLevelOneEntity extends SeqColEntity{
     @Basic(fetch = FetchType.LAZY)
     private JSONLevelOne seqColLevel1Object;
 
-    @Id
-    @Column(nullable = false)
-    @Enumerated(EnumType.STRING)
-    protected NamingConvention namingConvention;
+    @ElementCollection(fetch = FetchType.LAZY)
+    @CollectionTable(name = "seqcol_md", joinColumns =
+    @JoinColumn(name = "digest", nullable = false, updatable = false))
+    private Set<SeqColMetadataEntity> metadata;
 
-    public SeqColLevelOneEntity(String digest, NamingConvention namingConvention, JSONLevelOne jsonLevelOne){
-        super(digest, namingConvention);
+    public SeqColLevelOneEntity(String digest, JSONLevelOne jsonLevelOne){
+        super(digest);
         this.seqColLevel1Object = jsonLevelOne;
-        this.namingConvention = namingConvention;
+    }
+
+    public void addMetadata(SeqColMetadataEntity seqColMetadataEntity){
+        if(metadata == null) metadata = new HashSet<>();
+        metadata.add(seqColMetadataEntity);
     }
 
     @Override

src/main/java/uk/ac/ebi/eva/evaseqcol/entities/SeqColLevelTwoEntity.java

@@ -24,9 +24,4 @@ public SeqColLevelTwoEntity setDigest(String digest) {
         this.digest = digest;
         return this;
     }
-
-    public SeqColLevelTwoEntity setNamingConvention(NamingConvention convention) {
-        this.namingConvention = convention;
-        return this;
-    }
 }

src/main/java/uk/ac/ebi/eva/evaseqcol/entities/SeqColMetadataEntity.java

@@ -0,0 +1,47 @@
+package uk.ac.ebi.eva.evaseqcol.entities;
+
+import lombok.Data;
+import org.hibernate.annotations.CreationTimestamp;
+
+import javax.persistence.Column;
+import javax.persistence.Embeddable;
+import javax.persistence.EnumType;
+import javax.persistence.Enumerated;
+import javax.persistence.Temporal;
+import javax.persistence.TemporalType;
+import java.util.Date;
+
+@Data
+@Embeddable
+public class SeqColMetadataEntity {
+
+    @Column(name = "source_id")
+    private String sourceIdentifier;  // Eg: INSDC Acession
+
+    @Column(name = "source_url")
+    private String sourceUrl;
+
+    @Enumerated(EnumType.STRING)
+    @Column(name = "naming_convention")
+    private SeqColEntity.NamingConvention namingConvention;
+
+    @Column(name = "timestamp", updatable = false, columnDefinition="TIMESTAMP DEFAULT CURRENT_TIMESTAMP")
+    @Temporal(TemporalType.TIMESTAMP)
+    @CreationTimestamp
+    private Date timestamp;
+
+    public SeqColMetadataEntity setNamingConvention(SeqColEntity.NamingConvention namingConvention) {
+        this.namingConvention = namingConvention;
+        return this;
+    }
+
+    public SeqColMetadataEntity setSourceIdentifier(String sourceIdentifier) {
+        this.sourceIdentifier = sourceIdentifier;
+        return this;
+    }
+
+    public SeqColMetadataEntity setSourceUrl(String sourceUrl) {
+        this.sourceUrl = sourceUrl;
+        return this;
+    }
+}

src/main/java/uk/ac/ebi/eva/evaseqcol/repo/SeqColLevelOneRepository.java

@@ -1,9 +1,13 @@
 package uk.ac.ebi.eva.evaseqcol.repo;
 
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
 import org.springframework.stereotype.Repository;
 
 import uk.ac.ebi.eva.evaseqcol.entities.SeqColLevelOneEntity;
+import uk.ac.ebi.eva.evaseqcol.entities.SeqColMetadataEntity;
+
+import java.util.List;
 
 @Repository
 public interface SeqColLevelOneRepository extends JpaRepository<SeqColLevelOneEntity, String> {
@@ -14,4 +18,10 @@ public interface SeqColLevelOneRepository extends JpaRepository<SeqColLevelOneEn
     void removeSeqColLevelOneEntityByDigest(String digest);
 
     void deleteAll();
+
+    @Query(value = "select source_id, source_url, naming_convention, timestamp from seqcol_md where digest = ?1", nativeQuery = true)
+    List<Object[]> findMetadataBySeqColDigest(String digest);
+
+    @Query(value = "select source_id, source_url, naming_convention, timestamp from seqcol_md", nativeQuery = true)
+    List<Object[]> findAllMetadata();
 }

src/main/java/uk/ac/ebi/eva/evaseqcol/service/SeqColLevelOneService.java

@@ -8,14 +8,17 @@
 import uk.ac.ebi.eva.evaseqcol.entities.SeqColLevelOneEntity;
 import uk.ac.ebi.eva.evaseqcol.digests.DigestCalculator;
 import uk.ac.ebi.eva.evaseqcol.entities.SeqColLevelTwoEntity;
+import uk.ac.ebi.eva.evaseqcol.entities.SeqColMetadataEntity;
 import uk.ac.ebi.eva.evaseqcol.repo.SeqColLevelOneRepository;
 import uk.ac.ebi.eva.evaseqcol.utils.JSONExtData;
 import uk.ac.ebi.eva.evaseqcol.utils.JSONIntegerListExtData;
 import uk.ac.ebi.eva.evaseqcol.utils.JSONLevelOne;
 import uk.ac.ebi.eva.evaseqcol.utils.JSONStringListExtData;
 
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Date;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -62,12 +65,17 @@ public List<SeqColLevelOneEntity> getAllSeqColLevelOneObjects(){
 
     /**
      * Construct a seqCol level 1 entity out of three seqCol level 2 entities that
-     * hold names, lengths and sequences objects*/
+     * hold names, lengths and sequences objects
+     * TODO: Change the signature of this method and make it accept metadata object instead of namingconvention and source id*/
     public SeqColLevelOneEntity constructSeqColLevelOne(List<SeqColExtendedDataEntity<List<String>>> stringListExtendedDataEntities,
                                                         List<SeqColExtendedDataEntity<List<Integer>>> integerListExtendedDataEntities,
-                                                        SeqColEntity.NamingConvention convention) throws IOException {
+                                                        SeqColEntity.NamingConvention convention, String sourceId) throws IOException {
         SeqColLevelOneEntity levelOneEntity = new SeqColLevelOneEntity();
         JSONLevelOne jsonLevelOne = new JSONLevelOne();
+        SeqColMetadataEntity metadata = new SeqColMetadataEntity()
+                .setNamingConvention(convention)
+                .setSourceIdentifier(sourceId);
+        levelOneEntity.addMetadata(metadata);
 
         // Looping over List<String> types
         for (SeqColExtendedDataEntity<List<String>> dataEntity: stringListExtendedDataEntities) {
@@ -99,14 +107,13 @@ public SeqColLevelOneEntity constructSeqColLevelOne(List<SeqColExtendedDataEntit
         levelOneEntity.setSeqColLevel1Object(jsonLevelOne);
         String digest0 = digestCalculator.getSha512Digest(levelOneEntity.toString());
         levelOneEntity.setDigest(digest0);
-        levelOneEntity.setNamingConvention(convention);
         return levelOneEntity;
     }
 
     /**
      * Construct a Level 1 seqCol out of a Level 2 seqCol*/
     public SeqColLevelOneEntity constructSeqColLevelOne(
-            SeqColLevelTwoEntity levelTwoEntity, SeqColEntity.NamingConvention convention) throws IOException {
+            SeqColLevelTwoEntity levelTwoEntity, SeqColEntity.NamingConvention convention, String sourceId) throws IOException {
         DigestCalculator digestCalculator = new DigestCalculator();
         JSONExtData<List<String>> sequencesExtData = new JSONStringListExtData(levelTwoEntity.getSequences());
         JSONExtData<List<Integer>> lengthsExtData = new JSONIntegerListExtData(levelTwoEntity.getLengths());
@@ -151,7 +158,7 @@ public SeqColLevelOneEntity constructSeqColLevelOne(
                 lengthsExtEntity
         );
 
-        return constructSeqColLevelOne(stringListExtendedDataEntities,integerListExtendedDataEntities, convention);
+        return constructSeqColLevelOne(stringListExtendedDataEntities,integerListExtendedDataEntities, convention, sourceId);
     }
 
     /**
@@ -208,4 +215,28 @@ public List<SeqColExtendedDataEntity<List<Integer>>> constructIntegerListExtData
         return integerListExtendedDataEntities;
     }
 
+    public List<SeqColMetadataEntity> metadataObjectArrayListToMetadataList(List<Object[]> metadataArray) {
+        List<SeqColMetadataEntity> metadataList = new ArrayList<>();
+        for (Object[] metadataElements : metadataArray) {
+            SeqColMetadataEntity metadataEntity = new SeqColMetadataEntity();
+            metadataEntity.setSourceIdentifier((String) metadataElements[0]);
+            metadataEntity.setSourceUrl((String) metadataElements[1]);
+            metadataEntity.setNamingConvention(SeqColEntity.NamingConvention.valueOf(
+                    (String) metadataElements[2]
+            ));
+            metadataEntity.setTimestamp((Date) metadataElements[3]);
+            metadataList.add(metadataEntity);
+        }
+        return metadataList;
+    }
+
+    public List<SeqColMetadataEntity> getAllMetadata() {
+        List<Object[]> metadataArrayList = repository.findAllMetadata();
+        return metadataObjectArrayListToMetadataList(metadataArrayList);
+    }
+
+    public List<SeqColMetadataEntity> getMetadataBySeqcolDigest(String digest) {
+        List<Object[]> metadataArrayList = repository.findMetadataBySeqColDigest(digest);
+        return metadataObjectArrayListToMetadataList(metadataArrayList);
+    }
 }

src/main/java/uk/ac/ebi/eva/evaseqcol/service/SeqColService.java

@@ -14,6 +14,7 @@
 import uk.ac.ebi.eva.evaseqcol.entities.SeqColLevelOneEntity;
 import uk.ac.ebi.eva.evaseqcol.entities.SeqColExtendedDataEntity;
 import uk.ac.ebi.eva.evaseqcol.entities.SeqColLevelTwoEntity;
+import uk.ac.ebi.eva.evaseqcol.entities.SeqColMetadataEntity;
 import uk.ac.ebi.eva.evaseqcol.exception.AssemblyAlreadyIngestedException;
 import uk.ac.ebi.eva.evaseqcol.exception.AssemblyNotFoundException;
 import uk.ac.ebi.eva.evaseqcol.exception.AttributeNotDefinedException;
@@ -124,6 +125,10 @@ public Optional<? extends SeqColEntity> getSeqColByDigestAndLevel(String digest,
        }
     }
 
+    public List<SeqColMetadataEntity> getSeqColMetadataBySeqColDigest(String digest) {
+        return levelOneService.getMetadataBySeqcolDigest(digest);
+    }
+
     /**
      * Return the service info entity in a Map<String,Object> format
      * @see 'https://seqcol.readthedocs.io/en/dev/specification/#21-service-info'
@@ -165,6 +170,13 @@ public IngestionResultEntity fetchAndInsertAllSeqColInFastaFile(String accession
      * assembly report.
      * Return the list of level 0 digests of the inserted seqcol objects*/
     public IngestionResultEntity fetchAndInsertAllSeqColByAssemblyAccession(String assemblyAccession) throws IOException {
+        // Check for existing same source id
+        boolean sourceIdExists = levelOneService.getAllMetadata().stream()
+                .anyMatch(md -> md.getSourceIdentifier().equals(assemblyAccession));
+        if (sourceIdExists) {
+            logger.warn("Seqcol objects for assembly" + assemblyAccession + " have been already ingested. Nothing to ingest !");
+            throw new AssemblyAlreadyIngestedException(assemblyAccession);
+        }
         Optional<Map<String, Object>> seqColDataMap = ncbiSeqColDataSource.getAllPossibleSeqColExtendedData(assemblyAccession);
         return createSeqColObjectsAndInsert(seqColDataMap, assemblyAccession);
     }
@@ -206,8 +218,8 @@ public IngestionResultEntity createSeqColObjectsAndInsert(Optional<Map<String, O
 
             // Constructing seqCol Level One object
             SeqColLevelOneEntity levelOneEntity = levelOneService.constructSeqColLevelOne(
-                    seqColStringListExtDataEntities, seqColIntegerListExtDataEntities, extendedNamesEntity.getNamingConvention()
-                    );
+                    seqColStringListExtDataEntities, seqColIntegerListExtDataEntities, extendedNamesEntity.getNamingConvention(),
+                    assemblyAccession);
 
             try {
                 Optional<String> seqColDigest = insertSeqColL1AndL2( // TODO: Check for possible self invocation problem
@@ -227,7 +239,7 @@ public IngestionResultEntity createSeqColObjectsAndInsert(Optional<Map<String, O
             }
         }
         if (ingestionResultEntity.getNumberOfInsertedSeqcols() == 0) {
-            logger.warn("Seqcol objects for assembly " + assemblyAccession + " has been already ingested");
+            logger.warn("Seqcol objects for assembly " + assemblyAccession + " have been already ingested");
             throw new AssemblyAlreadyIngestedException(assemblyAccession);
         } else {
             return ingestionResultEntity;

src/test/java/uk/ac/ebi/eva/evaseqcol/io/SeqColGenerator.java

@@ -5,6 +5,7 @@
 import uk.ac.ebi.eva.evaseqcol.entities.SeqColEntity;
 import uk.ac.ebi.eva.evaseqcol.entities.SeqColLevelOneEntity;
 import uk.ac.ebi.eva.evaseqcol.entities.SeqColLevelTwoEntity;
+import uk.ac.ebi.eva.evaseqcol.entities.SeqColMetadataEntity;
 import uk.ac.ebi.eva.evaseqcol.utils.JSONLevelOne;
 
 import java.util.Arrays;
@@ -14,20 +15,26 @@
 @Component
 public class SeqColGenerator {
 
+    private final String GCA_ACCESSION = "GCA_000146045.2";
+
     /**
      * Return an example (might not be real) of a seqCol object level 1
      * The naming convention is set to GENBANK as a random choice*/
     public SeqColLevelOneEntity generateLevelOneEntity() {
         SeqColLevelOneEntity levelOneEntity = new SeqColLevelOneEntity();
         JSONLevelOne jsonLevelOne = new JSONLevelOne();
+        SeqColMetadataEntity metadata = new SeqColMetadataEntity()
+                .setNamingConvention(SeqColEntity.NamingConvention.GENBANK)
+                .setSourceIdentifier(GCA_ACCESSION)
+                .setSourceUrl("https://test.ncbi.datasourece.uk");
+        levelOneEntity.addMetadata(metadata);
         jsonLevelOne.setNames("mfxUkK3J5y7BGVW7hJWcJ3erxuaMX6xm");
         jsonLevelOne.setSequences("dda3Kzi1Wkm2A8I99WietU1R8J4PL-D6");
         jsonLevelOne.setLengths("Ms_ixPgQMJaM54dVntLWeovXSO7ljvZh");
         jsonLevelOne.setMd5DigestsOfSequences("_6iaYtcWw4TZaowlL7_64Wu9mbHpDUw4");
         jsonLevelOne.setSortedNameLengthPairs("QFuKs5Hh8uQwwUtnRxIf8W3zeJoFOp8Z");
         levelOneEntity.setSeqColLevel1Object(jsonLevelOne);
         levelOneEntity.setDigest("3mTg0tAA3PS-R1TzelLVWJ2ilUzoWfVq");
-        levelOneEntity.setNamingConvention(SeqColEntity.NamingConvention.GENBANK);
         return levelOneEntity;
     }
 
@@ -128,7 +135,6 @@ public SeqColLevelTwoEntity generateLevelTwoEntity() {
                 "YfHZgnpuJm4SN3RN4XL1VWWWZwTXtqw5"
         ));
         levelTwoEntity.setDigest("3mTg0tAA3PS-R1TzelLVWJ2ilUzoWfVq");
-        levelTwoEntity.setNamingConvention(SeqColEntity.NamingConvention.GENBANK);
         return levelTwoEntity;
     }
 }

src/test/java/uk/ac/ebi/eva/evaseqcol/io/SeqColWriter.java

@@ -146,7 +146,7 @@ public void create() throws IOException {
         extendedIntegerListDataEntitiesUcsc =
                 (List<SeqColExtendedDataEntity<List<Integer>>>) ucscExtendedDataMap.get("integerListExtDataList");
         levelOneEntityUcsc = levelOneService.constructSeqColLevelOne(
-                extendedStringListDataEntitiesUcsc, extendedIntegerListDataEntitiesUcsc, SeqColEntity.NamingConvention.UCSC);
+                extendedStringListDataEntitiesUcsc, extendedIntegerListDataEntitiesUcsc, SeqColEntity.NamingConvention.UCSC, GCA_ACCESSION);
         Optional<String> resultDigestUcsc = seqColService.addFullSequenceCollection(
                 levelOneEntityUcsc, extendedStringListDataEntitiesUcsc, extendedIntegerListDataEntitiesUcsc);
         if (resultDigestUcsc.isPresent()) {
@@ -163,7 +163,7 @@ public void create() throws IOException {
         extendedIntegerListDataEntitiesGenbank = (List<SeqColExtendedDataEntity<List<Integer>>>) genbankExtendedDataMap.get("integerListExtDataList");
 
         levelOneEntityGenbank = levelOneService.constructSeqColLevelOne(
-                extendedStringListDataEntitiesGenbank, extendedIntegerListDataEntitiesGenbank, SeqColEntity.NamingConvention.GENBANK);
+                extendedStringListDataEntitiesGenbank, extendedIntegerListDataEntitiesGenbank, SeqColEntity.NamingConvention.GENBANK, GCA_ACCESSION);
         Optional<String> resultDigestGenbank = seqColService.addFullSequenceCollection(
                 levelOneEntityGenbank, extendedStringListDataEntitiesGenbank, extendedIntegerListDataEntitiesGenbank);
         if (resultDigestGenbank.isPresent()) {