1 files changed, 127 insertions, 0 deletions
diff --git a/src/test/java/com/fasterxml/jackson/databind/deser/builder/BuilderWithTypeParametersTest.java b/src/test/java/com/fasterxml/jackson/databind/deser/builder/BuilderWithTypeParametersTest.java
new file mode 100644
index 000000000..7b8ddf6fa
--- /dev/null
+++ b/src/test/java/com/fasterxml/jackson/databind/deser/builder/BuilderWithTypeParametersTest.java
@@ -0,0 +1,127 @@
+package com.fasterxml.jackson.databind.deser.builder;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.BaseMapTest;
+import com.fasterxml.jackson.databind.MapperFeature;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import java.util.LinkedHashMap;
+import java.util.List;
+
+// [databind#921]: support infering type parameters from Builder
+public class BuilderWithTypeParametersTest
+    extends BaseMapTest
+{
+    public static class MyPOJO {
+      public String x;
+      public String y;
+
+      @JsonCreator
+      public MyPOJO(@JsonProperty("x") String x, @JsonProperty("y") String y) {
+        this.x = x;
+        this.y = y;
+      }
+    }
+
+    @JsonDeserialize(builder = MyGenericPOJO.Builder.class)
+    public static class MyGenericPOJO<T> {
+      private List<T> data;
+
+      private MyGenericPOJO(List<T> d) {
+        data = d;
+      }
+
+      public List<T> getData() {
+        return data;
+      }
+
+      // 28-Apr-2020, tatu: Note that as per [databind#921] the NAME of
+      //   type variable here MUST match that of enclosing class. This has
+      //   no semantic meaning to JDK or javac, but internally 
+      //   `MapperFeature.INFER_BUILDER_TYPE_BINDINGS` relies on this -- but
+      //   can not really validate it. So user just has to rely on bit of
+      //    black magic to use generic types with builders.
+      public static class Builder<T> {
+        private List<T> data;
+
+        public Builder<T> withData(List<T> d) {
+          data = d;
+          return this;
+        }
+
+        public MyGenericPOJO<T> build() {
+          return new MyGenericPOJO<T>(data);
+        }
+      }
+    }
+
+    public static class MyGenericPOJOWithCreator<T> {
+      private List<T> data;
+
+      private MyGenericPOJOWithCreator(List<T> d) {
+          data = d;
+      }
+
+      @JsonCreator
+      public static <T> MyGenericPOJOWithCreator<T> create(@JsonProperty("data") List<T> data) {
+          return new MyGenericPOJOWithCreator.Builder<T>().withData(data).build();
+      }
+
+      public List<T> getData() {
+          return data;
+      }
+
+      public static class Builder<T> {
+          private List<T> data;
+
+          public Builder<T> withData(List<T> d) {
+              data = d;
+              return this;
+          }
+
+          public MyGenericPOJOWithCreator<T> build() {
+              return new MyGenericPOJOWithCreator<T>(data);
+          }
+      }
+    }
+
+    public void testWithBuilderInferringBindings() throws Exception {
+        final ObjectMapper mapper = jsonMapperBuilder()
+                .enable(MapperFeature.INFER_BUILDER_TYPE_BINDINGS)
+                .build();
+        final String json = aposToQuotes("{ 'data': [ { 'x': 'x', 'y': 'y' } ] }");
+        final MyGenericPOJO<MyPOJO> deserialized =
+                mapper.readValue(json, new TypeReference<MyGenericPOJO<MyPOJO>>() {});
+        assertEquals(1, deserialized.data.size());
+        Object ob = deserialized.data.get(0);
+        assertNotNull(ob);
+        assertEquals(MyPOJO.class, ob.getClass());
+    }
+
+    public void testWithBuilderWithoutInferringBindings() throws Exception {
+        final ObjectMapper mapper = jsonMapperBuilder()
+                .disable(MapperFeature.INFER_BUILDER_TYPE_BINDINGS)
+                .build();
+      final String json = aposToQuotes("{ 'data': [ { 'x': 'x', 'y': 'y' } ] }");
+      final MyGenericPOJO<MyPOJO> deserialized =
+          mapper.readValue(json, new TypeReference<MyGenericPOJO<MyPOJO>>() {});
+      assertEquals(1, deserialized.data.size());
+      Object ob = deserialized.data.get(0);
+      assertNotNull(ob);
+      assertEquals(LinkedHashMap.class, ob.getClass());
+    }
+
+    public void testWithCreator() throws Exception {
+      final ObjectMapper mapper = new ObjectMapper();
+      final String json = aposToQuotes("{ 'data': [ { 'x': 'x', 'y': 'y' } ] }");
+      final MyGenericPOJOWithCreator<MyPOJO> deserialized =
+          mapper.readValue(json,
+                  new TypeReference<MyGenericPOJOWithCreator<MyPOJO>>() {});
+      assertEquals(1, deserialized.data.size());
+      Object ob = deserialized.data.get(0);
+      assertNotNull(ob);
+      assertEquals(MyPOJO.class, ob.getClass());
+    }
+  }