[core] Add type() method to SimpleMapper that takes a function that creates JsonAdapter (#328)

* Add pom descriptions for json-core and json-node + more consistent pom names

* [core] Add type() method to SimpleMapper that takes a function that creates JsonAdapter

Typically, the function is the constructor of the JsonAdapter. This makes it slightly cleaner to create the SimpleMapper.Type, for example:

    SimpleMapper mapper = SimpleMapper.builder().build();
    SimpleMapper.Type<MyCustomType> myType = mapper.type(MyAdapter::new);

Author: rbygrave

json-core/src/main/java/io/avaje/json/simple/DSimpleMapper.java

@@ -9,6 +9,7 @@
 
 import java.util.List;
 import java.util.Map;
+import java.util.function.Function;
 
 final class DSimpleMapper implements SimpleMapper {
 
@@ -34,6 +35,11 @@ public <T> Type<T> type(JsonAdapter<T> myAdapter) {
     return new DTypeMapper<>(myAdapter, jsonStream);
   }
 
+  @Override
+  public <T> Type<T> type(Function<SimpleMapper, JsonAdapter<T>> adapterFunction) {
+    return type(adapterFunction.apply(this));
+  }
+
   @Override
   public Type<Object> object() {
     return objectType;

json-core/src/main/java/io/avaje/json/simple/SimpleMapper.java

@@ -12,6 +12,7 @@
 import java.io.Writer;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Function;
 
 /**
  * A mapper for mapping to basic Java types.
@@ -136,6 +137,18 @@ static Builder builder() {
    */
   <T> Type<T> type(JsonAdapter<T> customAdapter);
 
+  /**
+   * Return a Type specific mapper using a function that creates a JsonAdapter.
+   * <p>
+   * Often the adapterFunction is the constructor of the custom JsonAdapter where
+   * the constructor takes SimpleMapper as the only argument.
+   *
+   * @param adapterFunction The function that creates a JsonAdapter.
+   * @param <T>             The type of the class to map to/from json.
+   * @return The Type specific mapper.
+   */
+  <T> Type<T> type(Function<SimpleMapper, JsonAdapter<T>> adapterFunction);
+
   default JsonExtract extract(Map<String, Object> map) {
     return new DExtract(map);
   }

json-core/src/test/java/io/avaje/json/simple/CustomAdapterTest.java

@@ -21,13 +21,15 @@ class CustomAdapterTest {
 
   @Test
   void mapUsingCustomAdapter() {
+    SimpleMapper mapper = SimpleMapper.builder().build();
+    SimpleMapper.Type<MyCustomType> myType = mapper.type(MyAdapter::new);
 
     MyCustomType source = new MyCustomType();
     source.foo = "hi";
     source.bar = 42;
-    String asJson = type.toJson(source);
+    String asJson = myType.toJson(source);
 
-    MyCustomType fromJson = type.fromJson(asJson);
+    MyCustomType fromJson = myType.fromJson(asJson);
 
     assertThat(fromJson.foo).isEqualTo(source.foo);
     assertThat(fromJson.bar).isEqualTo(source.bar);

json-node/src/main/java/io/avaje/json/node/JsonNodeMapper.java

@@ -13,6 +13,7 @@
 import java.io.Reader;
 import java.io.Writer;
 import java.lang.reflect.Type;
+import java.util.function.Function;
 
 /**
  * Provide JsonAdapters for the JsonNode types.
@@ -204,6 +205,18 @@ static Builder builder() {
    */
   <T> SimpleMapper.Type<T> type(JsonAdapter<T> customAdapter);
 
+  /**
+   * Return a Type specific mapper using a function that creates a JsonAdapter.
+   * <p>
+   * Often the adapterFunction is the constructor of the custom JsonAdapter where
+   * the constructor takes JsonNodeMapper as the only argument.
+   *
+   * @param adapterFunction The function that creates a JsonAdapter.
+   * @param <T>             The type of the class to map to/from json.
+   * @return The Type specific mapper.
+   */
+  <T> SimpleMapper.Type<T> type(Function<JsonNodeMapper, JsonAdapter<T>> adapterFunction);
+
   /**
    * Build the JsonNodeMapper.
    */

json-node/src/main/java/io/avaje/json/node/adapter/DJsonNodeMapper.java

@@ -9,6 +9,7 @@
 import io.avaje.json.stream.JsonStream;
 
 import java.lang.reflect.Type;
+import java.util.function.Function;
 
 final class DJsonNodeMapper implements JsonNodeMapper {
 
@@ -42,6 +43,11 @@ public <T> SimpleMapper.Type<T> type(JsonAdapter<T> customAdapter) {
     return new DMapper<>(customAdapter, jsonStream);
   }
 
+  @Override
+  public <T> SimpleMapper.Type<T> type(Function<JsonNodeMapper, JsonAdapter<T>> adapterFunction) {
+    return type(adapterFunction.apply(this));
+  }
+
   @Override
   public SimpleMapper.Type<JsonNode> nodeMapper() {
     return new DMapper<>(nodeAdapter, jsonStream);

json-node/src/test/java/io/avaje/json/node/CustomAdapterTest.java

@@ -21,9 +21,7 @@ class CustomAdapterTest {
 
   @Test
   void propertyNames() {
-
-    var adapter = new MyAdapter2(mapper);
-    SimpleMapper.Type<MyCustomType> type = mapper.type(adapter);
+    SimpleMapper.Type<MyCustomType> type = mapper.type(MyAdapter2::new);
 
     var source = as("a", 1);
     String asJson = type.toJson(source);