Rework the Jackson module as a Jackson Jr alternative (#1409)

Co-authored-by: Marvin Froeder <[email protected]>

Author: ashleyfrieze

README.md

@@ -360,6 +360,9 @@ public class Example {
 }
 ```
 
+For the lighter weight Jackson Jr, use `JacksonJrEncoder` and `JacksonJrDecoder` from
+the [Jackson Jr Module](./jackson-jr).
+
 ### Sax
 [SaxDecoder](./sax) allows you to decode XML in a way that is compatible with normal JVM and also Android environments.
 

jackson-jr/README.md

@@ -0,0 +1,43 @@
+Jackson Jr Codec
+===================
+
+This module adds support for encoding and decoding JSON via Jackson Jr. This
+is a significantly smaller and faster version of Jackson, which may be of benefit
+in smaller runtime containers.
+
+Add `JacksonJrEncoder` and/or `JacksonJrDecoder` to your `Feign.Builder` like so:
+
+```java
+GitHub github = Feign.builder()
+                     .encoder(new JacksonJrEncoder())
+                     .decoder(new JacksonJrDecoder())
+                     .target(GitHub.class, "https://api.github.com");
+```
+
+If you want to customize the `JSON` object that is used, provide it to the `JacksonJrEncoder` and `JacksonJrDecoder`:
+
+```java
+JSON json = Json.builder()
+                .register(JacksonAnnotationExtension.builder()
+                    .withVisibility(JsonAutoDetect.Value.defaultVisibility())
+                    .build())
+                .build();
+
+GitHub github = Feign.builder()
+                     .encoder(new JacksonJrEncoder(json))
+                     .decoder(new JacksonJrDecoder(json))
+                     .target(GitHub.class, "https://api.github.com");
+```
+
+Customisation is also possible by passing `JacksonJrExtension` objects
+into the constructor of the `JacksonJrEncoder` or `JacksonJrDecoder`:
+
+```java
+List<JacksonJrExtension> extensions = singletonList(JacksonAnnotationExtension.builder()
+        .withVisibility(JsonAutoDetect.Value.defaultVisibility())
+        .build());
+GitHub github = Feign.builder()
+                     .encoder(new JacksonJrEncoder(extensions))
+                     .decoder(new JacksonJrDecoder(extensions))
+                     .target(GitHub.class, "https://api.github.com");
+```

jackson-jr/pom.xml

@@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    Copyright 2012-2021 The Feign Authors
+
+    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.
+
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>io.github.openfeign</groupId>
+    <artifactId>parent</artifactId>
+    <version>11.3-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>feign-jackson-jr</artifactId>
+  <name>Feign Jackson Jr</name>
+  <description>Feign Jackson Jr</description>
+
+  <properties>
+    <main.basedir>${project.basedir}/..</main.basedir>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>feign-core</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>com.fasterxml.jackson.jr</groupId>
+      <artifactId>jackson-jr-objects</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>com.fasterxml.jackson.jr</groupId>
+      <artifactId>jackson-jr-annotation-support</artifactId>
+      <scope>test</scope>
+    </dependency>
+
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>feign-core</artifactId>
+      <type>test-jar</type>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+</project>

jackson-jr/src/main/java/feign/jackson/jr/JacksonJrDecoder.java

@@ -0,0 +1,107 @@
+/**
+ * Copyright 2012-2021 The Feign Authors
+ *
+ * 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 feign.jackson.jr;
+
+import com.fasterxml.jackson.jr.ob.JSON;
+import com.fasterxml.jackson.jr.ob.JSONObjectException;
+import com.fasterxml.jackson.jr.ob.JacksonJrExtension;
+import feign.Response;
+import feign.codec.DecodeException;
+import feign.codec.Decoder;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.Reader;
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * A {@link Decoder} that uses Jackson Jr to convert objects to String or byte representation.
+ */
+public class JacksonJrDecoder extends JacksonJrMapper implements Decoder {
+
+  @FunctionalInterface
+  interface Transformer {
+    Object apply(JSON mapper, Reader reader) throws IOException;
+  }
+
+  public JacksonJrDecoder() {
+    super();
+  }
+
+  /**
+   * Construct with a custom {@link JSON} to use for decoding
+   * 
+   * @param mapper the mapper to use
+   */
+  public JacksonJrDecoder(JSON mapper) {
+    super(mapper);
+  }
+
+  /**
+   * Construct with a series of {@link JacksonJrExtension} objects that are registered into the
+   * {@link JSON}
+   * 
+   * @param iterable the source of the extensions
+   */
+  public JacksonJrDecoder(Iterable<JacksonJrExtension> iterable) {
+    super(iterable);
+  }
+
+  @Override
+  public Object decode(Response response, Type type) throws IOException {
+
+    Transformer transformer = findTransformer(response, type);
+
+    if (response.body() == null) {
+      return null;
+    }
+    Reader reader = response.body().asReader(response.charset());
+    if (!reader.markSupported()) {
+      reader = new BufferedReader(reader, 1);
+    }
+    try {
+      // Read the first byte to see if we have any data
+      reader.mark(1);
+      if (reader.read() == -1) {
+        return null; // Eagerly returning null avoids "No content to map due to end-of-input"
+      }
+      reader.reset();
+      return transformer.apply(mapper, reader);
+    } catch (JSONObjectException e) {
+      if (e.getCause() instanceof IOException) {
+        throw (IOException) e.getCause();
+      }
+      throw e;
+    }
+  }
+
+  private static Transformer findTransformer(Response response, Type type) {
+    if (type instanceof Class) {
+      return (mapper, reader) -> mapper.beanFrom((Class<?>) type, reader);
+    }
+    if (type instanceof ParameterizedType) {
+      Type rawType = ((ParameterizedType) type).getRawType();
+      Type[] parameterType = ((ParameterizedType) type).getActualTypeArguments();
+      if (rawType.equals(List.class)) {
+        return (mapper, reader) -> mapper.listOfFrom((Class<?>) parameterType[0], reader);
+      }
+      if (rawType.equals(Map.class)) {
+        return (mapper, reader) -> mapper.mapOfFrom((Class<?>) parameterType[1], reader);
+      }
+    }
+    throw new DecodeException(500, "Cannot decode type: " + type.getTypeName(), response.request());
+  }
+}

jackson-jr/src/main/java/feign/jackson/jr/JacksonJrEncoder.java

@@ -0,0 +1,65 @@
+/**
+ * Copyright 2012-2021 The Feign Authors
+ *
+ * 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 feign.jackson.jr;
+
+import java.io.IOException;
+import java.lang.reflect.Type;
+import com.fasterxml.jackson.jr.ob.JSON;
+import com.fasterxml.jackson.jr.ob.JacksonJrExtension;
+import feign.RequestTemplate;
+import feign.codec.EncodeException;
+import feign.codec.Encoder;
+import static java.lang.String.format;
+
+/**
+ * A {@link Encoder} that uses Jackson Jr to convert objects to String or byte representation.
+ */
+public class JacksonJrEncoder extends JacksonJrMapper implements Encoder {
+
+  public JacksonJrEncoder() {
+    super();
+  }
+
+  /**
+   * Construct with a custom {@link JSON} to use for encoding
+   * 
+   * @param mapper the mapper to use
+   */
+  public JacksonJrEncoder(JSON mapper) {
+    super(mapper);
+  }
+
+  /**
+   * Construct with a series of {@link JacksonJrExtension} objects that are registered into the
+   * {@link JSON}
+   * 
+   * @param iterable the source of the extensions
+   */
+  public JacksonJrEncoder(Iterable<JacksonJrExtension> iterable) {
+    super(iterable);
+  }
+
+  @Override
+  public void encode(Object object, Type bodyType, RequestTemplate template) {
+    try {
+      if (bodyType == byte[].class) {
+        template.body(mapper.asBytes(object), null);
+      } else {
+        template.body(mapper.asString(object));
+      }
+    } catch (IOException e) {
+      throw new EncodeException(e.getMessage(), e);
+    }
+  }
+}

jackson-jr/src/main/java/feign/jackson/jr/JacksonJrMapper.java

@@ -0,0 +1,49 @@
+/**
+ * Copyright 2012-2021 The Feign Authors
+ *
+ * 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 feign.jackson.jr;
+
+import com.fasterxml.jackson.jr.ob.JSON;
+import com.fasterxml.jackson.jr.ob.JacksonJrExtension;
+
+/**
+ * Common implementation of the holder of a {@link JSON}, DRYing out construction.
+ */
+abstract class JacksonJrMapper {
+  protected final JSON mapper;
+
+  protected JacksonJrMapper() {
+    this(JSON.std);
+  }
+
+  /**
+   * Construct with a custom {@link JSON} to use for decoding/encoding
+   * 
+   * @param mapper the mapper to use
+   */
+  protected JacksonJrMapper(JSON mapper) {
+    this.mapper = mapper;
+  }
+
+  /**
+   * Construct with a series of {@link JacksonJrExtension} objects that are registered into the
+   * {@link JSON}
+   * 
+   * @param iterable the source of the extensions
+   */
+  protected JacksonJrMapper(Iterable<JacksonJrExtension> iterable) {
+    JSON.Builder builder = JSON.builder();
+    iterable.forEach(builder::register);
+    this.mapper = builder.build();
+  }
+}