fix: Hibernate would insert JSON as STRING (#944)

Hibernate tried by default to insert columns that had been annotated
with `@JdbcTypeCode(SqlTypes.JSON)` as a STRING instead of JSON. This
change adds a default type registration for JSON that does include the
correct type code with the value.

google-cloud-spanner-hibernate-dialect/pom.xml

@@ -54,6 +54,13 @@
       <artifactId>hibernate-ant</artifactId>
       <scope>test</scope>
     </dependency>
+    <!-- Jackson is needed for testing JSON. -->
+    <dependency>
+      <groupId>com.fasterxml.jackson.core</groupId>
+      <artifactId>jackson-databind</artifactId>
+      <version>2.15.2</version>
+      <scope>test</scope>
+    </dependency>
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-spanner</artifactId>

google-cloud-spanner-hibernate-dialect/src/main/java/com/google/cloud/spanner/hibernate/SpannerDialect.java

@@ -22,9 +22,13 @@
 import static org.hibernate.type.SqlTypes.NUMERIC;
 
 import com.google.cloud.spanner.hibernate.schema.SpannerForeignKeyExporter;
+import com.google.cloud.spanner.jdbc.JsonType;
+import java.sql.CallableStatement;
 import java.sql.Connection;
+import java.sql.PreparedStatement;
 import java.sql.SQLException;
 import org.hibernate.HibernateException;
+import org.hibernate.boot.model.TypeContributions;
 import org.hibernate.boot.model.relational.Sequence;
 import org.hibernate.dialect.unique.UniqueDelegate;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
@@ -37,6 +41,7 @@
 import org.hibernate.query.sqm.internal.DomainParameterXref;
 import org.hibernate.query.sqm.mutation.spi.SqmMultiTableInsertStrategy;
 import org.hibernate.query.sqm.tree.insert.SqmInsertStatement;
+import org.hibernate.service.ServiceRegistry;
 import org.hibernate.sql.ast.SqlAstTranslator;
 import org.hibernate.sql.ast.SqlAstTranslatorFactory;
 import org.hibernate.sql.ast.spi.StandardSqlAstTranslatorFactory;
@@ -50,6 +55,13 @@
 import org.hibernate.tool.schema.internal.StandardSequenceExporter;
 import org.hibernate.tool.schema.internal.StandardUniqueKeyExporter;
 import org.hibernate.tool.schema.spi.Exporter;
+import org.hibernate.type.SqlTypes;
+import org.hibernate.type.descriptor.ValueBinder;
+import org.hibernate.type.descriptor.WrapperOptions;
+import org.hibernate.type.descriptor.java.JavaType;
+import org.hibernate.type.descriptor.jdbc.BasicBinder;
+import org.hibernate.type.descriptor.jdbc.JsonAsStringJdbcType;
+import org.hibernate.type.descriptor.jdbc.spi.JdbcTypeRegistry;
 
 /** Hibernate 6.x dialect for Cloud Spanner. */
 public class SpannerDialect extends org.hibernate.dialect.SpannerDialect {
@@ -65,6 +77,33 @@ public int executeInsert(
       throw new HibernateException("Multi-table inserts are not supported for Cloud Spanner");
     }
   }
+
+  private static class SpannerJsonJdbcType extends JsonAsStringJdbcType {
+    private SpannerJsonJdbcType() {
+      super(SqlTypes.LONG32VARCHAR, null);
+    }
+
+    @Override
+    public <X> ValueBinder<X> getBinder(JavaType<X> javaType) {
+      return new BasicBinder<X>(javaType, this) {
+        @Override
+        protected void doBind(PreparedStatement st, X value, int index, WrapperOptions options)
+            throws SQLException {
+          final String json = ((SpannerJsonJdbcType) getJdbcType()).toString(
+              value, getJavaType(), options);
+          st.setObject(index, json, JsonType.VENDOR_TYPE_NUMBER);
+        }
+
+        @Override
+        protected void doBind(CallableStatement st, X value, String name, WrapperOptions options)
+            throws SQLException {
+          final String json = ((SpannerJsonJdbcType) getJdbcType()).toString(
+              value, getJavaType(), options);
+          st.setObject(name, json, JsonType.VENDOR_TYPE_NUMBER);
+        }
+      };
+    }
+  }
 
   /**
    * Property name that can be used to disable sequence support in the Cloud Spanner dialect. You
@@ -122,6 +161,15 @@ protected String columnType(int sqlTypeCode) {
     return super.columnType(sqlTypeCode);
   }
 
+  @Override
+  protected void registerColumnTypes(
+      TypeContributions typeContributions, ServiceRegistry serviceRegistry) {
+    super.registerColumnTypes(typeContributions, serviceRegistry);
+    JdbcTypeRegistry jdbcTypeRegistry =
+        typeContributions.getTypeConfiguration().getJdbcTypeRegistry();
+    jdbcTypeRegistry.addDescriptorIfAbsent(new SpannerJsonJdbcType());
+  }
+
   @Override
   public Exporter<Table> getTableExporter() {
     return this.spannerTableExporter;

google-cloud-spanner-hibernate-dialect/src/test/java/com/google/cloud/spanner/hibernate/it/SampleModelIT.java

@@ -242,15 +242,20 @@ public void testSaveTrack() {
   @Test
   public void testSaveVenue() {
     try (Session session = sessionFactory.openSession()) {
-      Transaction transaction = session.beginTransaction();
-      // TODO: Set VenueDescription fields and verify these in Hibernate 6.
-      //       Hibernate 5 does not support JSON without additional plugins.
-      Venue venue = new Venue("Venue 1", new VenueDescription());
-      session.save(venue);
+      final Transaction transaction = session.beginTransaction();
+      VenueDescription description = new VenueDescription();
+      description.setCapacity(100);
+      description.setLocation("some-location");
+      description.setType("Arena");
+      Venue venue = new Venue("Venue 1", description);
+      session.persist(venue);
       transaction.commit();
 
       session.refresh(venue);
       assertEquals("Venue 1", venue.getName());
+      assertEquals(100, venue.getDescription().getCapacity());
+      assertEquals("some-location", venue.getDescription().getLocation());
+      assertEquals("Arena", venue.getDescription().getType());
     }
   }
 

google-cloud-spanner-hibernate-dialect/src/test/java/com/google/cloud/spanner/hibernate/it/model/Venue.java

@@ -20,17 +20,19 @@
 package com.google.cloud.spanner.hibernate.it.model;
 
 import jakarta.persistence.CascadeType;
+import jakarta.persistence.Column;
 import jakarta.persistence.Entity;
 import jakarta.persistence.GeneratedValue;
 import jakarta.persistence.GenerationType;
 import jakarta.persistence.Id;
 import jakarta.persistence.OneToMany;
-import jakarta.persistence.Transient;
 import java.io.Serializable;
 import java.util.List;
 import org.hibernate.annotations.GenericGenerator;
+import org.hibernate.annotations.JdbcTypeCode;
 import org.hibernate.annotations.Parameter;
 import org.hibernate.id.enhanced.SequenceStyleGenerator;
+import org.hibernate.type.SqlTypes;
 
 /**
  * Venue entity.
@@ -94,8 +96,8 @@ public void setLocation(String location) {
    * This field maps to a JSON column in the database. The value is automatically
    * serialized/deserialized to a {@link VenueDescription} instance.
    */
-  // TODO: Make this non-transient when we support Hibernate 6.
-  @Transient
+  @Column(columnDefinition = "json")
+  @JdbcTypeCode(SqlTypes.JSON)
   private VenueDescription description;
 
   @OneToMany(mappedBy = "venue", cascade = CascadeType.ALL)