Add Moshi #2182
Add Moshi #2182
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WalkthroughThis pull request introduces Moshi support for JSON encoding and decoding in Feign. It adds Changes
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Review Status
Actionable comments generated: 9
Files ignored due to filter (2)
- moshi/pom.xml
- pom.xml
Files selected for processing (11)
- README.md (1 hunks)
- moshi/README.md (1 hunks)
- moshi/src/main/java/feign/moshi/MoshiDecoder.java (1 hunks)
- moshi/src/main/java/feign/moshi/MoshiEncoder.java (1 hunks)
- moshi/src/main/java/feign/moshi/MoshiFactory.java (1 hunks)
- moshi/src/test/java/feign/moshi/MoshiDecoderTest.java (1 hunks)
- moshi/src/test/java/feign/moshi/MoshiEncoderTest.java (1 hunks)
- moshi/src/test/java/feign/moshi/UpperZoneJSONAdapter.java (1 hunks)
- moshi/src/test/java/feign/moshi/VideoGame.java (1 hunks)
- moshi/src/test/java/feign/moshi/Zone.java (1 hunks)
- moshi/src/test/java/feign/moshi/examples/GithubExample.java (1 hunks)
Files skipped from review due to trivial changes (5)
- README.md
- moshi/src/test/java/feign/moshi/MoshiDecoderTest.java
- moshi/src/test/java/feign/moshi/MoshiEncoderTest.java
- moshi/src/test/java/feign/moshi/VideoGame.java
- moshi/src/test/java/feign/moshi/Zone.java
Additional comments (Suppressed): 2
moshi/src/main/java/feign/moshi/MoshiFactory.java (1)
- 30-30: The
addmethod ofMoshi.Buildertakes two parameters: a type and a JSON adapter for that type. Here, you're passing the class of the adapter itself as the type, which might not be what you intend. You should pass the class of the type that the adapter handles instead. Please verify if this is the intended behavior.moshi/src/main/java/feign/moshi/MoshiDecoder.java (1)
- 30-73: The
MoshiDecoderclass is well implemented. It provides multiple constructors to allow for different levels of customization of theMoshiinstance used for decoding. Thedecodemethod handles various response scenarios appropriately, including 404 and 204 status codes, and null bodies. Error handling is also done correctly, with a specific catch block forJsonDataExceptionthat rethrows any underlyingIOException. The reader is ensured to be closed in a finally block, which is good practice to prevent resource leaks.
moshi/README.md
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| Moshi Codec | ||
| =================== | ||
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| This module adds support for encoding and decoding JSON via the Moshi library. | ||
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| Add `MoshiEncoder` and/or `MoshiDecoder` to your `Feign.Builder` like so: | ||
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| ```java | ||
| GitHub github = Feign.builder() | ||
| .encoder(new MoshiEncoder()) | ||
| .decoder(new MoshiDecoder()) | ||
| .target(GitHub.class, "https://api.github.com"); | ||
| ``` | ||
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| ### Map<String, Object> and Numbers | ||
| The default constructors of `MoshiEncoder` and `MoshiDecoder` decoder numbers in | ||
| `Map<String, Object>` as Integer type. This prevents reading `{"counter", "1"}` | ||
| as `Map.of("counter", 1.0)`. | ||
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| To change this, please use constructors that accept a Moshi object. |
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The documentation update is clear and provides a good overview of how to use the new Moshi encoder and decoder. It also explains the default behavior for number decoding in Map<String, Object> and how to change it. However, it would be beneficial to include an example of using custom JsonAdapter instances with the MoshiEncoder and MoshiDecoder, as mentioned in the PR summary.
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| public static void main(String... args) { | ||
| GitHub github = Feign.builder().encoder(new MoshiEncoder()) | ||
| .decoder(new MoshiDecoder()) | ||
| .target(GitHub.class, "https://api.github.com"); | ||
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| System.out.println("Let's fetch and print a list of the contributors to this library."); | ||
| List<Contributor> contributors = github.contributors("netflix", "feign"); | ||
| for (Contributor contributor : contributors) { | ||
| System.out.println(contributor.login + " (" + contributor.contributions + ")"); | ||
| } | ||
| } |
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The main method in the GithubExample class is directly making a network call to fetch contributors from GitHub. This could potentially block the main thread if the network call takes too long. Consider moving this network call to a separate thread or using asynchronous programming techniques.
| static class Contributor { | ||
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| String login; | ||
| int contributions; | ||
| } |
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The Contributor class is currently using package-private fields for login and contributions. While this might work within the context of this example, it's generally a good practice to encapsulate these fields with getter and setter methods to maintain data integrity and control over access.
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| private final Moshi moshi; | ||
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| public MoshiEncoder() { | ||
| this.moshi = new Moshi.Builder().build(); | ||
| } | ||
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| public MoshiEncoder(Moshi moshi) { | ||
| this.moshi = moshi; | ||
| } | ||
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| public MoshiEncoder(Iterable<JsonAdapter<?>> adapters) { | ||
| this(MoshiFactory.create(adapters)); | ||
| } | ||
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| @Override | ||
| public void encode(Object object, Type bodyType, RequestTemplate template) { | ||
| JsonAdapter<Object> jsonAdapter = moshi.adapter(bodyType).indent(" "); | ||
| template.body(jsonAdapter.toJson(object)); | ||
| } | ||
| } |
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The MoshiEncoder class is well implemented. It provides three constructors to create an instance of the encoder with a default Moshi instance, a custom Moshi instance, or a set of JsonAdapter instances. The encode method correctly uses the Moshi instance to create a JsonAdapter for the body type and encode the object into JSON format. However, it's worth noting that the indent(" ") call in line 41 will add two spaces of indentation to the output JSON. This can increase the size of the payload, especially for large objects. If this is not a requirement, consider removing it to optimize the performance.
- JsonAdapter<Object> jsonAdapter = moshi.adapter(bodyType).indent(" ");
+ JsonAdapter<Object> jsonAdapter = moshi.adapter(bodyType);| static Moshi create(Iterable<JsonAdapter<?>> adapters) { | ||
| Moshi.Builder builder = new Moshi.Builder(); | ||
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| for (JsonAdapter<?> adapter : adapters) { | ||
| builder.add(adapter.getClass(), adapter); | ||
| } | ||
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| return builder.build(); | ||
| } |
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The create method is declared as static, which means it can be called without creating an instance of MoshiFactory. However, the method is package-private (default access modifier), which restricts its visibility to classes within the same package. If this method is intended to be used outside of the feign.moshi package, consider changing its access modifier to public.
- static Moshi create(Iterable<JsonAdapter<?>> adapters) {
+ public static Moshi create(Iterable<JsonAdapter<?>> adapters) {| @Override | ||
| public Object decode(Response response, Type type) throws IOException { | ||
| JsonAdapter<Object> jsonAdapter = moshi.adapter(type); | ||
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| if (response.status() == 404 || response.status() == 204) | ||
| return Util.emptyValueOf(type); | ||
| if (response.body() == null) | ||
| return null; | ||
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| Reader reader = response.body().asReader(UTF_8); | ||
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| try { | ||
| return parseJson(jsonAdapter, reader); | ||
| } catch (JsonDataException e) { | ||
| if (e.getCause() != null && e.getCause() instanceof IOException) { | ||
| throw (IOException) e.getCause(); | ||
| } | ||
| throw e; | ||
| } finally { | ||
| ensureClosed(reader); | ||
| } | ||
| } |
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Consider adding error handling for other potential HTTP status codes that may require special handling. For example, a 400 (Bad Request) or 500 (Internal Server Error) might need to be handled differently than a 404 or 204. This would make your decoder more robust and adaptable to different server responses.
if (response.status() == 404 || response.status() == 204)
+ else if (response.status() >= 400)
+ throw new IOException("Server returned HTTP status code " + response.status());
return Util.emptyValueOf(type);| private Object parseJson(JsonAdapter<Object> jsonAdapter, Reader reader) throws IOException { | ||
| String targetString = CharStreams.toString(reader); | ||
| return jsonAdapter.fromJson(targetString); | ||
| } |
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While converting the entire JSON body into a string before parsing it with Moshi works, it can be inefficient for large JSON bodies as it requires storing the entire JSON body in memory as a string. Instead, you can parse the JSON directly from the Reader which is more memory-efficient and can handle larger JSON bodies.
- String targetString = CharStreams.toString(reader);
- return jsonAdapter.fromJson(targetString);
+ return jsonAdapter.fromJson(reader);| public void toJson(JsonWriter out, LinkedList<Zone> value) throws IOException { | ||
| out.beginArray(); | ||
| for (Zone zone : value) { | ||
| out.beginObject(); | ||
| for (Map.Entry<String, Object> entry : zone.entrySet()) { | ||
| out.name(entry.getKey()).value(entry.getValue().toString().toUpperCase()); | ||
| } | ||
| out.endObject(); | ||
| } | ||
| out.endArray(); | ||
| } |
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The toJson method does not handle null values. If the value parameter or any of the Zone objects within it are null, this will result in a NullPointerException. Consider adding null checks to prevent this.
public void toJson(JsonWriter out, LinkedList<Zone> value) throws IOException {
+ if (value == null) {
+ out.nullValue();
+ return;
+ }
out.beginArray();
for (Zone zone : value) {
+ if (zone == null) {
+ out.nullValue();
+ continue;
+ }
out.beginObject();
for (Map.Entry<String, Object> entry : zone.entrySet()) {
out.name(entry.getKey()).value(entry.getValue().toString().toUpperCase());
}
out.endObject();
}
out.endArray();
}| public LinkedList<Zone> fromJson(JsonReader in) throws IOException { | ||
| LinkedList<Zone> zones = new LinkedList<>(); | ||
| in.beginArray(); | ||
| while (in.hasNext()) { | ||
| in.beginObject(); | ||
| Zone zone = new Zone(); | ||
| while (in.hasNext()) { | ||
| zone.put(in.nextName(), in.nextString().toUpperCase()); | ||
| } | ||
| in.endObject(); | ||
| zones.add(zone); | ||
| } | ||
| in.endArray(); | ||
| return zones; |
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Similar to the toJson method, the fromJson method does not handle null values. If the JSON input contains null values, this could lead to unexpected behavior. Consider adding null checks to prevent this.
public LinkedList<Zone> fromJson(JsonReader in) throws IOException {
LinkedList<Zone> zones = new LinkedList<>();
in.beginArray();
while (in.hasNext()) {
in.beginObject();
Zone zone = new Zone();
while (in.hasNext()) {
+ String name = in.nextName();
+ String value = in.nextString();
+ if (name != null && value != null) {
+ zone.put(name, value.toUpperCase());
+ }
}
in.endObject();
zones.add(zone);
}
in.endArray();
return zones;
}
* Add Moshi * Update README.md --------- Co-authored-by: Vikramaditya Chhapwale <[email protected]>
* Add Moshi * Update README.md --------- Co-authored-by: Vikramaditya Chhapwale <[email protected]>
Hello,
This PR adds Moshi as a module in Feign. It comes with an implemented encode and decode method which uses Moshi as well as a constructor to add your own custom adapter. I wrote tests using two different ways one can create a JSONAdapter using Moshi.
This is in response to an issue I opened on #2176.
Summary by CodeRabbit
MoshiEncoderandMoshiDecoderclasses that can be configured with aFeign.Builderinstance.MoshiEncoderandMoshiDecoderthat accept a collection ofJsonAdapterinstances.