# rxjava2-json
**Repository Path**: mirrors_davidmoten/rxjava2-json
## Basic Information
- **Project Name**: rxjava2-json
- **Description**: RxJava2 utitilies for consuming streaming json
- **Primary Language**: Unknown
- **License**: Apache-2.0
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No
## Statistics
- **Stars**: 0
- **Forks**: 0
- **Created**: 2020-08-08
- **Last Updated**: 2026-10-03
## Categories & Tags
**Categories**: Uncategorized
**Tags**: None
## README
# rxjava2-json
[](https://maven-badges.herokuapp.com/maven-central/com.github.davidmoten/rxjava2-json)
[](https://codecov.io/gh/davidmoten/rxjava2-json)
RxJava 2 utilities for JSON.
Status: *in development*
## About
Project goals are these:
* present queries on streams of JSON text as an RxJava stream (`Flowable`, `Maybe`, `Single`)
* reduce memory, cpu and io use by only parsing JSON parts that are queried
* support backpressure
* make a certain class of JSON query efficient and easily expressable in RxJava 2.x
## Examples
We'll use this JSON to show some extraction methods:
```json
{
"books": [
{
"isbn": "9781593275846",
"title": "Eloquent JavaScript, Second Edition",
"subtitle": "A Modern Introduction to Programming",
"author": "Marijn Haverbeke",
"published": "2014-12-14T00:00:00.000Z",
"publisher": "No Starch Press",
"pages": 472,
"description": "JavaScript lies at the heart of almost every modern web application, from social apps to the newest browser-based games. Though simple for beginners to pick up and play with, JavaScript is a flexible, complex language that you can use to build full-scale applications.",
"website": "http://eloquentjavascript.net/"
},
...
}
```
### Extract a repeated element as a Flowable
Here we count the distinct authors from the input JSON:
```java
long count =
Json.stream(inputStream)
.fieldArray("books") //
.field("author") //
.map(node -> node.asText()) //
.distinct() //
.count() //
.blockingGet(); .
```
### Parse an array and map each item to an object
Given a streaming array of JSON like this:
```
[{"name":"City","datetime":"2020-01-10T08:00:00.000","aqi":"36"}
,{"name":"City","datetime":"2020-01-10T07:00:00.000","aqi":"36"}
,{"name":"City","datetime":"2020-01-10T06:00:00.000","aqi":"39"}
,{"name":"City","datetime":"2020-01-10T05:00:00.000","aqi":"43"}
,{"name":"City","datetime":"2020-01-10T04:00:00.000","aqi":"50"}
,{"name":"City","datetime":"2020-01-10T03:00:00.000","aqi":"54"}
,{"name":"City","datetime":"2020-01-10T02:00:00.000","aqi":"61"}
,{"name":"City","datetime":"2020-01-10T01:00:00.000","aqi":"73"}
,{"name":"City","datetime":"2020-01-10T00:00:00.000","aqi":"85"}
...
```
Mapping class:
```java
import java.util.Date;
import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonProperty;
public class Record {
@JsonProperty("datetime")
@JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd'T'HH:mm:ss.SSS", timezone = "ADST")
public Date time;
@JsonProperty("aqi")
public Double value;
@JsonProperty("name")
public String name;
}
```
Process it like this to map each row to a Jackson annotated class:
```java
Json
.stream(in)
.arrayNode()
.flatMapPublisher(node -> node.values(Record.class))
// ignore some records
.filter(rec -> rec.value != null && rec.value > 50)
// print the values to stdout
.forEach(rec -> System.out.println(rec.value));
```
### Parse an array and do what you like with each element
Given a streaming array of JSON like this:
```
[{"name":"City","datetime":"2020-01-10T08:00:00.000","aqi":"36"}
,{"name":"City","datetime":"2020-01-10T07:00:00.000","aqi":"36"}
,{"name":"City","datetime":"2020-01-10T06:00:00.000","aqi":"39"}
,{"name":"City","datetime":"2020-01-10T05:00:00.000","aqi":"43"}
,{"name":"City","datetime":"2020-01-10T04:00:00.000","aqi":"50"}
,{"name":"City","datetime":"2020-01-10T03:00:00.000","aqi":"54"}
,{"name":"City","datetime":"2020-01-10T02:00:00.000","aqi":"61"}
,{"name":"City","datetime":"2020-01-10T01:00:00.000","aqi":"73"}
,{"name":"City","datetime":"2020-01-10T00:00:00.000","aqi":"85"}
...
```
Process it like this to extract what we like from each element using `JsonNode`:
```java
Json
.stream(in)
.arrayNode()
.flatMapPublisher(node -> node.values())
// we now have a stream of JsonNode
.map(node -> node.get("aqi").asInt())
// ignore some records
.filter(x -> x != null && x > 50)
// print the values to stdout
.forEach(System.out::println);
```
## Usage notes
There is no method that takes an InputStream/Reader factory and autocloses it (using the Flowable.using method). This is because under the covers a single `JsonParser` element is emitted which is a stateful singleton and really just a pointer to the current position of the parser in the JSON input.
For those methods that return `Stream` because the created InputStream/Reader may be closed before the `JsonParser` has finished reading. Note that you might not notice this effect because a JsonParser uses a BufferedInputStream and if your input is smaller than the buffer size, closing the InputStream/Reader early may not have an effect because the whole stream was read into the buffer already.