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Add recipe for @FromJson with non-String input.

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This commit is contained in:
David Mihola 2015-10-08 09:38:09 +02:00
parent 2032353ef7
commit 19c41eb18f
3 changed files with 166 additions and 117 deletions
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76
README.md
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@ -132,6 +132,82 @@ Voila:
}
```
Note that the method annotated with `@FromJson` does not need to take a String as an argument. Rather it can take
input of any type and Moshi will first parse the JSON to an object of that type and then use the `@FromJson`
method to produce the desired final value. Conversely, the method annotated with `@ToJson` does not have to produce
a String.
Assume, for example, that we have to parse a JSON in which the date and time of an event are represented as two
separate strings.
```json
{
"title": "Blackjack tournament",
"begin_date": "20151010",
"begin_time": "17:04"
}
```
We would like to combine these two fields into one string to facilitate the date parsing at a
later point. That is, while the `EventJson` class corresponds to the JSON structure directly, we would rather
have an `Event` that looks like below (while we are at it, we are also changing the variable names to
CamelCase).
```java
class EventJson {
String title;
String begin_date;
String begin_time;
}
class Event {
String title;
String beginDateAndTime;
}
```
To enable Moshi to do that transformation automatically we define a class with the `@FromJson`
(and `@ToJson`) methods:
```java
class EventJsonAdapter {
@FromJson
Event eventFromJson(EventJson eventJson) {
Event event = new Event();
event.title = eventJson.title;
event.beginDateAndTime = eventJson.begin_date + " " + eventJson.begin_time;
return event;
}
@ToJson
EventJson eventToJson(Event event) {
EventJson json = new EventJson();
json.title = event.title;
json.begin_date = event.beginDateAndTime.substring(0, 8);
json.begin_time = event.beginDateAndTime.substring(9, 14);
return json;
}
}
```
And register it with Moshi.
```java
Moshi moshi = new Moshi.Builder()
.add(new EventJsonAdapter())
.build();
```
We can now use Moshi to parse the JSON directly to an `Event`.
```java
JsonAdapter<Event> jsonAdapter = moshi.adapter(Event.class);
Event event = jsonAdapter.fromJson(json);
```
### Fails Gracefully
Automatic databinding almost feels like magic. But unlike the black magic that typically accompanies

117
examples/src/main/java/com/squareup/moshi/recipes/CustomJsonAdapter.java
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@ -1,117 +0,0 @@
/*
* Copyright (C) 2015 Square, Inc.
*
* 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 com.squareup.moshi.recipes;
import com.squareup.moshi.JsonAdapter;
import com.squareup.moshi.JsonReader;
import com.squareup.moshi.JsonWriter;
import com.squareup.moshi.Moshi;
import java.io.IOException;
public final class CustomJsonAdapter {
public void run() throws Exception {
// for some reason our JSON has date and time as separate fields -
// we will use a custom JsonAdapter<Event> to clean that up during parsing
String json = ""
+ "{\n"
+ " \"title\": \"Blackjack tournament\",\n"
+ " \"beginDate\": \"20151006\",\n"
+ " \"beginTime\": \"15:59\"\n"
+ "}\n";
Moshi moshi = new Moshi.Builder()
.add(Event.class, new EventAdapter())
.build();
JsonAdapter<Event> jsonAdapter = moshi.adapter(Event.class);
Event event = jsonAdapter.fromJson(json);
System.out.println(event);
System.out.println(jsonAdapter.toJson(event));
}
public static void main(String[] args) throws Exception {
new CustomJsonAdapter().run();
}
public static final class EventAdapter extends JsonAdapter<Event> {
@Override
public Event fromJson(JsonReader jsonReader) throws IOException {
String title = null;
String beginDate = null;
String beginTime = null;
jsonReader.beginObject();
while (jsonReader.hasNext()) {
String name = jsonReader.nextName();
if (name.equals("title")) {
title = jsonReader.nextString();
} else if (name.equals("beginDate")) {
beginDate = jsonReader.nextString();
} else if (name.equals("beginTime")) {
beginTime = jsonReader.nextString();
} else {
jsonReader.skipValue();
}
}
jsonReader.endObject();
final String beginDateAndTime = (beginDate != null) && (beginTime != null) ?
beginDate + " " + beginTime : null;
return new Event(title, beginDateAndTime);
}
@Override
public void toJson(JsonWriter jsonWriter, Event event) throws IOException {
jsonWriter.beginObject();
if (event.title != null) {
jsonWriter.name("title");
jsonWriter.value(event.title);
}
if (event.beginDateAndTime != null) {
jsonWriter.name("beginDate");
jsonWriter.value(event.beginDateAndTime.substring(0, 8));
jsonWriter.name("beginTime");
jsonWriter.value(event.beginDateAndTime.substring(9, 14));
}
jsonWriter.endObject();
}
}
public static final class Event {
public final String title;
public final String beginDateAndTime;
public Event(String title, String beginDateAndTime) {
this.title = title;
this.beginDateAndTime = beginDateAndTime;
}
@Override
public String toString() {
return "Event{" +
"title='" + title + '\'' +
", beginDateAndTime=" + beginDateAndTime +
'}';
}
}
}

90
examples/src/main/java/com/squareup/moshi/recipes/FromJsonWithoutStrings.java Normal file
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@ -0,0 +1,90 @@
/*
* Copyright (C) 2015 Square, Inc.
*
* 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 com.squareup.moshi.recipes;
import com.squareup.moshi.FromJson;
import com.squareup.moshi.JsonAdapter;
import com.squareup.moshi.Moshi;
import com.squareup.moshi.ToJson;
public final class FromJsonWithoutStrings {
public void run() throws Exception {
// for some reason our JSON has date and time as separate fields -
// we will clean that up during parsing: Moshi will first parse
// the JSON directly to an EventJson and from that the EventJsonAdapter
// will create the actual Event
String json = ""
+ "{\n"
+ " \"title\": \"Blackjack tournament\",\n"
+ " \"begin_date\": \"20151010\",\n"
+ " \"begin_time\": \"17:04\"\n"
+ "}\n";
Moshi moshi = new Moshi.Builder()
.add(new EventJsonAdapter())
.build();
JsonAdapter<Event> jsonAdapter = moshi.adapter(Event.class);
Event event = jsonAdapter.fromJson(json);
System.out.println(event);
System.out.println(jsonAdapter.toJson(event));
}
public static void main(String[] args) throws Exception {
new FromJsonWithoutStrings().run();
}
private static final class EventJson {
String title;
String begin_date;
String begin_time;
}
public static final class Event {
String title;
String beginDateAndTime;
@Override
public String toString() {
return "Event{" +
"title='" + title + '\'' +
", beginDateAndTime='" + beginDateAndTime + '\'' +
'}';
}
}
private static final class EventJsonAdapter {
@FromJson
Event eventFromJson(EventJson eventJson) {
Event event = new Event();
event.title = eventJson.title;
event.beginDateAndTime = eventJson.begin_date + " " + eventJson.begin_time;
return event;
}
@ToJson
EventJson eventToJson(Event event) {
EventJson json = new EventJson();
json.title = event.title;
json.begin_date = event.beginDateAndTime.substring(0, 8);
json.begin_time = event.beginDateAndTime.substring(9, 14);
return json;
}
}
}