add a static way to retrieve the default instance (#396)

Author: SentryMan

README.md

@@ -95,7 +95,7 @@ For types we cannot annotate with `@Json` we can place `@Json.Import(TypeToimpor
 
 ```java
 // build using defaults
-Jsonb jsonb = Jsonb.builder().build();
+Jsonb jsonb = Jsonb.instance();
 
 JsonType<Customer> customerType = jsonb.type(Customer.class);
 
@@ -116,7 +116,7 @@ to include when serializing to json.
 For example:
 
 ```java
-Jsonb jsonb = Jsonb.builder().build();
+Jsonb jsonb = Jsonb.instance();
 
 JsonType<Customer> customerType = jsonb.type(Customer.class);
 
@@ -226,7 +226,7 @@ public final class AddressJsonAdapter implements JsonAdapter<Address>, ViewBuild
 
 ## Based on Moshi
 
-`avaje-jsonb` is based on [Moshi](https://github.com/square/moshi) with some changes as summarised below:
+`avaje-jsonb` was based on [Moshi](https://github.com/square/moshi) with some changes as summarised below:
 
 #### Changes from Moshi
 - Generates Java source code (rather than Kotlin)
@@ -245,7 +245,6 @@ public final class AddressJsonAdapter implements JsonAdapter<Address>, ViewBuild
 - Add `@Json.Import` to generate adapters for types that we can't put the annotation on (types we might not 'own')
 - Add Mixin feature similar to Jackson Mixins
 - Add Types.listOf(), Types.setOf(), Types.mapOf() helper methods
-- Provide an SPI with the view to target other json-p implementations JSONP/Yasson, GSON, etc
 - Adds more common Java types with default built-in support - java.time types, java.util.UUID
 - Adds support for json views
 

blackbox-test/src/test/java/org/example/customer/ALBResponseTest.java

@@ -10,7 +10,7 @@
 
 class ALBResponseTest {
 
-  private final Jsonb jsonb = Jsonb.builder().build();
+  private final Jsonb jsonb = Jsonb.instance();
 
   @Test
   void toJson() {

jsonb/src/main/java/io/avaje/jsonb/Jsonb.java

@@ -107,6 +107,16 @@ static Builder builder() {
     return DefaultBootstrap.builder();
   }
 
+  /**
+   * Get the default Jsonb instance with all generated adapters configured.
+   *
+   * <p>This is a faster alternative to {@code Jsonb.builder().build()} that will return the same
+   * singleton instance.
+   */
+  static Jsonb instance() {
+    return DefaultBootstrap.defaultInstance();
+  }
+
   /**
    * Return json content for the given object.
    * <p>

jsonb/src/main/java/io/avaje/jsonb/core/DJsonb.java

@@ -258,7 +258,7 @@ public int hashCode() {
    */
   static final class DBuilder implements Jsonb.Builder {
 
-    private static final Jsonb DEFAULT = Jsonb.builder().build();
+    static final Jsonb DEFAULT = Jsonb.builder().build();
 
     private final List<AdapterFactory> factories = new ArrayList<>();
     private boolean failOnUnknown;

jsonb/src/main/java/io/avaje/jsonb/core/DefaultBootstrap.java

@@ -13,4 +13,8 @@ public final class DefaultBootstrap {
   public static Jsonb.Builder builder() {
     return new DJsonb.DBuilder();
   }
+
+  public static Jsonb defaultInstance() {
+    return DJsonb.DBuilder.DEFAULT;
+  }
 }