Add MapUserType to support converstion between Map and hstore (#443)

core/src/main/java/google/registry/persistence/GenericCollectionUserType.java

@@ -14,20 +14,17 @@
 
 package google.registry.persistence;
 
-import java.io.Serializable;
 import java.sql.Array;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Types;
 import java.util.Collection;
-import java.util.Objects;
 import org.hibernate.HibernateException;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
-import org.hibernate.usertype.UserType;
 
 /** Generic Hibernate user type to store/retrieve Java collection as an array in Cloud SQL. */
-public abstract class GenericCollectionUserType<T extends Collection> implements UserType {
+public abstract class GenericCollectionUserType<T extends Collection> extends MutableUserType {
 
   abstract T getNewCollection();
 
@@ -62,16 +59,6 @@ public abstract class GenericCollectionUserType<T extends Collection> implements
     return new int[] {getColumnType().getTypeCode()};
   }
 
-  @Override
-  public boolean equals(Object x, Object y) throws HibernateException {
-    return Objects.equals(x, y);
-  }
-
-  @Override
-  public int hashCode(Object x) throws HibernateException {
-    return x == null ? 0 : x.hashCode();
-  }
-
   @Override
   public Object nullSafeGet(
       ResultSet rs, String[] names, SharedSessionContractImplementor session, Object owner)
@@ -98,30 +85,4 @@ public abstract class GenericCollectionUserType<T extends Collection> implements
     Array arr = st.getConnection().createArrayOf(getColumnType().getTypeName(), list.toArray());
     st.setArray(index, arr);
   }
-
-  // TODO(b/147489651): Investigate how to properly implement the below methods.
-  @Override
-  public Object deepCopy(Object value) throws HibernateException {
-    return value;
-  }
-
-  @Override
-  public boolean isMutable() {
-    return false;
-  }
-
-  @Override
-  public Serializable disassemble(Object value) throws HibernateException {
-    return (Serializable) value;
-  }
-
-  @Override
-  public Object assemble(Serializable cached, Object owner) throws HibernateException {
-    return cached;
-  }
-
-  @Override
-  public Object replace(Object original, Object target, Object owner) throws HibernateException {
-    return original;
-  }
 }

core/src/main/java/google/registry/persistence/MapUserType.java

@@ -0,0 +1,57 @@
+// Copyright 2020 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.persistence;
+
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Types;
+import java.util.Map;
+import org.hibernate.HibernateException;
+import org.hibernate.engine.spi.SharedSessionContractImplementor;
+import org.hibernate.usertype.UserType;
+
+/**
+ * A custom {@link UserType} used to convert a Java {@link Map<String, String>} to/from PostgreSQL
+ * hstore type. Per this <a href="https://www.postgresql.org/docs/current/hstore.html">doc</a>, as
+ * hstore keys and values are simply text strings, the type of key and value in the Java map has to
+ * be {@link String} as well.
+ */
+public class MapUserType extends MutableUserType {
+
+  @Override
+  public int[] sqlTypes() {
+    return new int[] {Types.OTHER};
+  }
+
+  @Override
+  public Class returnedClass() {
+    return Map.class;
+  }
+
+  @Override
+  public Object nullSafeGet(
+      ResultSet rs, String[] names, SharedSessionContractImplementor session, Object owner)
+      throws HibernateException, SQLException {
+    return rs.getObject(names[0]);
+  }
+
+  @Override
+  public void nullSafeSet(
+      PreparedStatement st, Object value, int index, SharedSessionContractImplementor session)
+      throws HibernateException, SQLException {
+    st.setObject(index, value);
+  }
+}

core/src/main/java/google/registry/persistence/MutableUserType.java

@@ -0,0 +1,63 @@
+// Copyright 2020 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.persistence;
+
+import java.io.Serializable;
+import java.util.Objects;
+import org.hibernate.HibernateException;
+import org.hibernate.usertype.UserType;
+
+/**
+ * An abstract class represents a mutable Hibernate user type which implements related methods
+ * defined in {@link UserType}.
+ */
+public abstract class MutableUserType implements UserType {
+
+  @Override
+  public boolean equals(Object x, Object y) throws HibernateException {
+    return Objects.equals(x, y);
+  }
+
+  @Override
+  public int hashCode(Object x) throws HibernateException {
+    return x == null ? 0 : x.hashCode();
+  }
+
+  // TODO(b/147489651): Investigate how to properly implement the below methods.
+  @Override
+  public Object deepCopy(Object value) throws HibernateException {
+    return value;
+  }
+
+  @Override
+  public boolean isMutable() {
+    return false;
+  }
+
+  @Override
+  public Serializable disassemble(Object value) throws HibernateException {
+    return (Serializable) value;
+  }
+
+  @Override
+  public Object assemble(Serializable cached, Object owner) throws HibernateException {
+    return cached;
+  }
+
+  @Override
+  public Object replace(Object original, Object target, Object owner) throws HibernateException {
+    return original;
+  }
+}

core/src/main/java/google/registry/persistence/NomulusPostgreSQLDialect.java

@@ -24,6 +24,7 @@ public class NomulusPostgreSQLDialect extends PostgreSQL95Dialect {
     registerColumnType(Types.VARCHAR, "text");
     registerColumnType(Types.TIMESTAMP_WITH_TIMEZONE, "timestamptz");
     registerColumnType(Types.TIMESTAMP, "timestamptz");
+    registerColumnType(Types.OTHER, "hstore");
     for (ArrayColumnType arrayType : ArrayColumnType.values()) {
       registerColumnType(arrayType.getTypeCode(), arrayType.getTypeDdlName());
     }