2단계 - Proxy

src/main/java/persistence/sql/dml/InsertQueryBuilder.java

@@ -5,7 +5,6 @@
 import persistence.sql.entity.EntityColumn;
 import persistence.sql.entity.EntityColumns;
 import persistence.sql.entity.EntityTable;
-import persistence.sql.entity.OneToManyColumn;
 
 import java.lang.reflect.Field;
 import java.util.Arrays;
@@ -30,18 +29,20 @@ private String columnsClause(EntityColumns entityColumns, Object parentEntity) {
                 .collect(Collectors.toList());
 
         if (parentEntity != null) {
-            OneToManyColumn oneToManyColumn = new OneToManyColumn(findOneToManyField(parentEntity.getClass()));
-            columns.add(oneToManyColumn.getForeignKeyColumnName());
+            List<Field> oneToManyFields = findOneToManyFields(parentEntity.getClass());
+            for (Field oneToManyField : oneToManyFields) {
+                EntityColumn oneToManyColumn = EntityColumn.from(oneToManyField);
+                columns.add(oneToManyColumn.getOneToManyColumn().getForeignKeyColumnName());
+            }
         }
 
         return String.join(", ", columns);
     }
 
-    private Field findOneToManyField(Class<?> clazz) {
+    private List<Field> findOneToManyFields(Class<?> clazz) {
         return Arrays.stream(clazz.getDeclaredFields())
                 .filter(field -> field.isAnnotationPresent(OneToMany.class))
-                .findFirst()
-                .orElseThrow(() -> new RuntimeException("OneToMany 필드를 찾을 수 없습니다."));
+                .collect(Collectors.toList());
     }
 
     private String valueClause(EntityColumns entityColumns, Object object, Long parentId) {

src/main/java/persistence/sql/entity/EntityColumns.java

@@ -1,7 +1,5 @@
 package persistence.sql.entity;
 
-import jakarta.persistence.JoinColumn;
-import jakarta.persistence.OneToMany;
 import jakarta.persistence.Transient;
 
 import java.lang.reflect.Field;
@@ -27,14 +25,6 @@ public List<EntityColumn> getColumns() {
         return columns;
     }
 
-    public EntityColumn getEntityColumn(Field field) {
-        return columns.stream()
-                .filter(entityColumn -> entityColumn.getColumnName().equals(field.getName()))
-                .findFirst()
-                .orElse(null);
-    }
-
-
     public String getIdFieldName() {
         for (EntityColumn column : columns) {
             if (column.isPrimaryKey()) {

src/main/java/persistence/sql/entity/OneToManyColumn.java

@@ -7,13 +7,15 @@
 
 public class OneToManyColumn {
     private final Field field;
+    private Class<?> joinEntityClass;
 
     public OneToManyColumn(Field field) {
         this.field = field;
+        this.joinEntityClass = (Class<?>) ((ParameterizedType) field.getGenericType()).getActualTypeArguments()[0];
     }
 
     public Class<?> getJoinEntityClass() {
-        return (Class<?>) ((ParameterizedType) field.getGenericType()).getActualTypeArguments()[0];
+        return joinEntityClass;
     }
 
     public String getForeignKeyColumnName() {

src/test/java/persistence/sql/entity/EntityPersisterTest.java

@@ -86,10 +86,10 @@ void insert2() throws SQLException {
         List<OrderItem> selectResult = jdbcTemplate.query(selectQuery, new EntityRowMapper<>(OrderItem.class));
 
         assertThat(selectResult).hasSize(2);
-        assertThat(selectResult.get(0).getProduct()).isEqualTo(orderItem1.getProduct());
-        assertThat(selectResult.get(0).getQuantity()).isEqualTo(orderItem1.getQuantity());
-        assertThat(selectResult.get(1).getProduct()).isEqualTo(orderItem2.getProduct());
-        assertThat(selectResult.get(1).getQuantity()).isEqualTo(orderItem2.getQuantity());
+        assertThat(selectResult.get(0).getProduct()).isEqualTo("감자");
+        assertThat(selectResult.get(0).getQuantity()).isEqualTo(3);
+        assertThat(selectResult.get(1).getProduct()).isEqualTo("고구마");
+        assertThat(selectResult.get(1).getQuantity()).isEqualTo(1);
 
         jdbcTemplate.execute("drop table order_items");
         jdbcTemplate.execute("drop table orders");