JsonSurfer

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A streaming JsonPath processor in Java

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# JsonSurfer - Let's surf on Json!

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## Why JsonSurfer

* Streaming

No need to deserialize entire json into memory.
    
* JsonPath

Selectively extract json data by the power of JsonPath.

* Stoppable

JsonSurfer is built on stoppable SAX-like interface that allows the processor to stop itself if necessary.

* Non-Blocking

JsonSurfer is event-driven and offers non-blocking parser interface.

* Binary format

Support multiple binary data formats including Avro, CBOR, Protobuf, Smile and Ion.

## Getting started

### [What is JsonPath?](http://goessner.net/articles/JsonPath/)

* Supported JsonPath operator in JsonSurfer:

* JsonSurfer is available in cetral maven repository.

JsonSurfer has drivers for most of popular json libraries including: Gson, Jackson, FastJson and JsonSimple. Choose one and add to your POM.

```xml

<dependency>
    <groupId>com.github.jsurfer</groupId>
    <artifactId>jsurfer-gson</artifactId>
    <version>1.6.3</version>
</dependency>

<dependency>
    <groupId>com.github.jsurfer</groupId>
    <artifactId>jsurfer-jackson</artifactId>
    <version>1.6.3</version>
</dependency>

<dependency>
    <groupId>com.github.jsurfer</groupId>
    <artifactId>jsurfer-fastjson</artifactId>
    <version>1.6.3</version>
</dependency>

<dependency>
    <groupId>com.github.jsurfer</groupId>
    <artifactId>jsurfer-jsonsimple</artifactId>
    <version>1.6.3</version>
</dependency>

```

### Usage:

#### Create your JsonSurfer:

* JsonSurfer has flexible constructor. You can create yourself or pick a prebuilt one according the json library you used:
1. Gson
```java
        // use gson parser and use gson provider use to deserialize json into gson model i.e.com.google.gson.JsonElement
        JsonSurfer surfer = new JsonSurfer(GsonParser.INSTANCE, GsonProvider.INSTANCE);
```
or
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
```
2. Jackson
```java
        JsonSurfer surfer = new JsonSurfer(JacksonParser.INSTANCE, JacksonProvider.INSTANCE);
```
or
```java
        JsonSurfer surfer = JsonSurferJackson.INSTANCE;
```
3. JsonSimple
```java
        // use json-simple parser and json-simple provider to deserialize json into json-simple model i.e.org.json.simple.JSONObject or org.json.simple.JSONArray
        JsonSurfer surfer = new JsonSurfer(JsonSimpleParser.INSTANCE, JsonSimpleProvider.INSTANCE);
```
or
```java
        JsonSurfer surfer = JsonSurferJsonSimple.INSTANCE;
```
4. Fastjson
```java
        JsonSurfer surfer = new JsonSurfer(FastJsonParser.INSTANCE, FastJsonProvider.INSTANCE);
```
or
```java
        JsonSurfer surfer = JsonSurferFastJson.INSTANCE;
```
#### Collect value by JsonPath
```java
        Collector collector = surfer.collector(sample);
        ValueBox<String> box1 = collector.collectOne("$.store.book[1].category", String.class);
        ValueBox<Object> box2 = collector.collectOne("$.store.book[2].isbn");
        ValueBox<Collection<Object>> box3 = collector.collectAll("$.store.book[*]");
        collector.exec(); // make sure exec() invoked before getting value from boxes
        box1.get();
        box2.get();
        box3.get();
```
#### 【DEPRECATED】 Collect the first matched value and stop immediately
```java
        JsonSurfer jsonSurfer = JsonSurferGson.INSTANCE;
        Object singleResult = jsonSurfer.collectOne(sample, "$.store.book[0]");
```
#### 【DEPRECATED】 Colllect every matched value into a collection
```java
        JsonSurfer jsonSurfer = JsonSurferGson.INSTANCE;
        Collection<Object> multipleResults = jsonSurfer.collectAll(sample, "$.store.book[*]");
```
#### "Surfing" in Json and collecting matched value in the listeners
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
        surfer.configBuilder()
                .bind("$.store.book[*]", new JsonPathListener() {
                    @Override
                    public void onValue(Object value, ParsingContext context) {
                        System.out.println(value);
                    }
                })
                .buildAndSurf(sample);
```
#### Reuse listener binding.
SurfingConfiguration is thread-safe as long as your listeners are stateless.
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
        SurfingConfiguration config = surfer.configBuilder()
                .bind("$.store.book[*]", new JsonPathListener() {
                    @Override
                    public void onValue(Object value, ParsingContext context) {
                        System.out.println(value);
                    }
                })
                .build();        
        surfer.surf(sample1, config);
        surfer.surf(sample2, config);
```
#### Compiled JsonPath
JsonPath object is immutable and can be reused safely.

**Tips:** Most of JsonSurfer API have two version: accepting raw JsonPath string or JsonPath object. The latter is always faster than the former without compiling JsonPath.
```java
        JsonPath compiledPath = JsonPathCompiler.compile("$..book[1,3]['author','title']");
        String value = surfer.collectOne(read("sample.json"), String.class, compiledPath);
```
#### JsonPath Filters
* Filter operators

| Operator                  |   Description     |
| :-----------------------: |:-----------------:|
| ==                        | equal             |
| <                         | less than         |
| >                         | greater than      |

You can use logical operators '&&' and '||' to create more complex filter expression. For example:
```
$.store.book[?(@.price < 10 || @.category && @.isbn && @.price>10)].volumes[?(@.chapter == 1)]
```

#### Resolver API:
* Limitation: **Wildcard** and **Recursive Descent** are **NOT** supported.
* As of 1.2.6, JsonSurfer provides another way of processing json. You can directly resolve value with JsonPath from a well-built DOM like HashMap or even POJO:
```java
        Book book = new Book();
        book.setAuthor("Leo");
        book.setCategory("Fiction");
        book.setPrice(100.0d);
        book.setTitle("JsonSurfer is great!");
        System.out.print(compile("$.author").resolve(book, new PoJoResolver()));
```
which prints "Leo".
```java
        List<String> list = Arrays.asList("foo", "bar");
        HashMap<String, Object> map = new HashMap<String, Object>();
        map.put("list", list);
        System.out.println(compile("$.list[1]").resolve(map, JavaCollectionProvider.INSTANCE));
```
which prints "bar".
* If you want to **process POJO with full JsonPath feature**, you can convert the POJO into binary format and then surfer on it.
#### Binaray format (Jackson only)
By importing [Jackson binary format backend](https://github.com/FasterXML/jackson-dataformats-binary), JsonSurfer is capable to surfer with multiple binary object representation formats such as Avro, CBOR, Protobuf(A known bug to be fixed in Jackson 2.9.6), Smile and Ion.

For example, if you want to surfer with CBOR data, firstly, CBOR format backend need to be imported as dependency.
```
    <dependency>
        <groupId>com.fasterxml.jackson.dataformat</groupId>
        <artifactId>jackson-dataformat-cbor</artifactId>
        <version>${jackson.version}</version>
    </dependency>
```
Then create a JsonSurfer with CBOR-backed JacksonParser and surfer as usual
```java
    surfer = new JsonSurfer(new JacksonParser(new CBORFactory()), provider);
```
Find more examples here: https://github.com/jsurfer/JsonSurfer/blob/master/jsurfer-all/src/test/java/org/jsfr/json/JacksonParserTest.java
#### Share data among processors
Since JsonSurfer emit data in the way of callback, it would be difficult if one of your processing depends one another. Therefore a simple transient map is added for sharing data among your processors. Following unit test shows how to use it:
```java
        surfer.configBuilder().bind("$.store.book[1]", new JsonPathListener() {
            @Override
            public void onValue(Object value, ParsingContext context) {
                context.save("foo", "bar");
            }
        }).bind("$.store.book[2]", new JsonPathListener() {
            @Override
            public void onValue(Object value, ParsingContext context) {
                assertEquals("bar", context.load("foo", String.class));
            }
        }).bind("$.store.book[0]", new JsonPathListener() {
            @Override
            public void onValue(Object value, ParsingContext context) {
                assertNull(context.load("foo", String.class));
            }
        }).buildAndSurf(read("sample.json"));
```
#### Control parsing
* How to pause and resume parsing.
```java
    SurfingConfiguration config = surfer.configBuilder()
            .bind("$.store.book[0]", new JsonPathListener() {
                @Override
                public void onValue(Object value, ParsingContext context) {
                    LOGGER.info("The first pause");
                    context.pause();
                }
            })
            .bind("$.store.book[1]", new JsonPathListener() {
                @Override
                public void onValue(Object value, ParsingContext context) {
                    LOGGER.info("The second pause");
                    context.pause();
                }
            }).build();
    ResumableParser parser = surfer.getResumableParser(read("sample.json"), config);
    assertFalse(parser.resume());
    LOGGER.info("Start parsing");
    parser.parse();
    LOGGER.info("Resume from the first pause");
    assertTrue(parser.resume());
    LOGGER.info("Resume from the second pause");
    assertTrue(parser.resume());
    LOGGER.info("Parsing stopped");
    assertFalse(parser.resume());
```
* Completely stop parsing. Refer to [Stoppable parsing](#stoppable-parsing)
#### Java 8 Streams API support
As of 1.4, JsonSurfer can create an iterator from Json and JsonPath. Matched value can be pulled from the iterator one by one without loading entire json into memory.
```java
    Iterator iterator = surfer.iterator(read("sample.json"), JsonPathCompiler.compile("$.store.book[*]"));
```
Java8 user can also convert the iterator into a Stream
```java
    Stream<Object> targetStream = StreamSupport.stream(
          Spliterators.spliteratorUnknownSize(iterator, Spliterator.ORDERED),
          false);
```
Functions implmented by Streams API
```java
    public static Stream<Object> toStream(String json, String path) {
        Iterator<Object> iterator = JsonSurferJackson.INSTANCE.iterator(json, JsonPathCompiler.compile(path));
        return StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, Spliterator.ORDERED), false);
    }

public static void main(String[] s) throws Exception {
        String json = "[1,3,5,7,11]";
        // Count
        System.out.println(toStream(json, "$[*]").count());
        // Max
        toStream(json, "$[*]").mapToInt(o -> ((LongNode) o).asInt()).max().ifPresent(System.out::println);
        // Min
        toStream(json, "$[*]").mapToInt(o -> ((LongNode) o).asInt()).min().ifPresent(System.out::println);
        // Average
        toStream(json, "$[*]").mapToDouble(o -> ((LongNode) o).asDouble()).average().ifPresent(System.out::println);
    }
```
#### Non-Blocking parsing
As of 1.4, JsonSurfer support non-blocking parsing for JacksonParser. You can achieve 100% non-blocking JSON processing with JsonSurfer in a NIO application. Let's take a Vertx request handler as an example:
```java
    Vertx vertx = Vertx.vertx();
    HttpServer server = vertx.createHttpServer(new HttpServerOptions());
    JsonSurfer surfer = JsonSurferJackson.INSTANCE;
    SurfingConfiguration config = surfer.configBuilder()
            .bind("$[*]", (JsonPathListener) (value, context) -> {
                // Handle json
                System.out.println(value);
            }).build();
    server.requestHandler(request -> {
        NonBlockingParser parser = surfer.createNonBlockingParser(config);
        request.handler(buffer -> {
            byte[] bytes = buffer.getBytes();
            System.out.println("Received " + bytes.length + " bytes");
            parser.feed(bytes, 0, bytes.length);
        });
        request.endHandler(aVoid -> {
            parser.endOfInput();
            System.out.println("End of request");
            request.response().end();
        });
    }).listen(8080);
```
### Examples

Sample Json:
```javascript
{
    "store": {
        "book": [
            {
                "category": "reference",
                "author": "Nigel Rees",
                "title": "Sayings of the Century",
                "price": 8.95
            },
            {
                "category": "fiction",
                "author": "Evelyn Waugh",
                "title": "Sword of Honour",
                "price": 12.99
            },
            {
                "category": "fiction",
                "author": "Herman Melville",
                "title": "Moby Dick",
                "isbn": "0-553-21311-3",
                "price": 8.99
            },
            {
                "category": "fiction",
                "author": "J. R. R. Tolkien",
                "title": "The Lord of the Rings",
                "isbn": "0-395-19395-8",
                "price": 22.99
            }
        ],
        "bicycle": {
            "color": "red",
            "price": 19.95
        }
    },
    "expensive": 10
}
```

#### Find the authors of all books: 
```javascript
$.store.book[*].author
```
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
        surfer.configBuilder()
                .bind("$.store.book[*].author", new JsonPathListener() {
                    @Override
                    public void onValue(Object value, ParsingContext context) {
                        System.out.println(value);
                    }
                })
                .buildAndSurf(sample);
```
Output
```
"Nigel Rees"
"Evelyn Waugh"
"Herman Melville"
"J. R. R. Tolkien"
```
#### All authors
```javascript
$..author
```
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
        surfer.configBuilder()
                .bind("$..author", new JsonPathListener() {
                    @Override
                    public void onValue(Object value, ParsingContext context) {
                        System.out.println(value);
                    }
                })
                .buildAndSurf(sample);
```
Output
```
"Nigel Rees"
"Evelyn Waugh"
"Herman Melville"
"J. R. R. Tolkien"
```
#### All things in store
```javascript
$.store.*
```
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
        surfer.configBuilder()
                .bind("$.store.*", new JsonPathListener() {
                    @Override
                    public void onValue(Object value, ParsingContext context) {
                        System.out.println(value);
                    }
                })
                .buildAndSurf(sample);
```
Output
```
[{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95},{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99},{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99},{"category":"fiction","author":"J. R. R. Tolkien","title":"The Lord of the Rings","isbn":"0-395-19395-8","price":22.99}]
{"color":"red","price":19.95}
```
#### The price of everything in the store
```javascript
$.store..price
```
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
        surfer.configBuilder()
                .bind("$.store..price", new JsonPathListener() {
                    @Override
                    public void onValue(Object value, ParsingContext context) {
                        System.out.println(value);
                    }
                })
                .buildAndSurf(sample);
```
Output
```
8.95
12.99
8.99
22.99
19.95
```
#### The third book
```javascript
$..book[2]
```
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
        surfer.configBuilder()
                .bind("$..book[2]", new JsonPathListener() {
                    @Override
                    public void onValue(Object value, ParsingContext context) {
                        System.out.println(value);
                    }
                })
                .buildAndSurf(sample);
```
Output
```
{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99}
```
#### The first two books
```javascript
$..book[0,1]
```
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
        surfer.configBuilder()
                .bind("$..book[0,1]", new JsonPathListener() {
                    @Override
                    public void onValue(Object value, ParsingContext context) {
                        System.out.println(value);
                    }
                })
                .buildAndSurf(sample);
```
Output
```
{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95}
{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99}
```
#### Filter all books whose price equals to 8.95
```javascript
$.store.book[?(@.price==8.95)]
```
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
        surfer.configBuilder()
                .bind("$.store.book[?(@.price==8.95)]", new JsonPathListener() {
                    @Override
                    public void onValue(Object value, ParsingContext context) {
                        System.out.println(value);
                    }
                })
                .buildAndSurf(sample);
```
Output
```
{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95}
```
#### Filter all books which belong to fiction category
```javascript
$.store.book[?(@.category=='fiction')]
```
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
        surfer.configBuilder()
                .bind("$.store.book[?(@.category=='fiction')]", new JsonPathListener() {
                    @Override
                    public void onValue(Object value, ParsingContext context) {
                        System.out.println(value);
                    }
                })
                .buildAndSurf(sample);
```
Output
```
{"category":"fiction","author":"Evelyn Waugh","title":"Sword of Honour","price":12.99}
{"category":"fiction","author":"Herman Melville","title":"Moby Dick","isbn":"0-553-21311-3","price":8.99}
{"category":"fiction","author":"J. R. R. Tolkien","title":"The Lord of the Rings","isbn":"0-395-19395-8","price":22.99}
```
#### All books matching regex
```javascript
$.store.book[?(@.author=~/tolkien/i)]
```
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
        surfer.configBuilder()
                .bind("$.store.book[?(@.author=~/tolkien/i)]')]", new JsonPathListener() {
                    @Override
                    public void onValue(Object value, ParsingContext context) {
                        System.out.println(value);
                    }
                })
                .buildAndSurf(sample);
```
Output
```
{"author":"J. R. R. Tolkien","price":22.99,"isbn":"0-395-19395-8","category":"fiction","title":"The Lord of the Rings"}
```
#### Stoppable parsing
The parsing is stopped when the first book found and printed.
```javascript
$..book[0,1]
```
```java
        JsonSurfer surfer = JsonSurferGson.INSTANCE;
        surfer.configBuilder()
                .bind("$..book[0,1]", new JsonPathListener() {
                    @Override
                    public void onValue(Object value, ParsingContext context) {                        
                        System.out.println(value);
                        context.stop();
                    }
                })
                .buildAndSurf(sample);
```
Output
```
{"category":"reference","author":"Nigel Rees","title":"Sayings of the Century","price":8.95}
```
### Benchmark

* JsonSurfer is fast !!! The benchmark is powered by [JMH](http://openjdk.java.net/projects/code-tools/jmh/)

```
Benchmark                                                       Mode  Cnt       Score       Error  Units
BenchmarkCollectSingleValue.benchmarkFastjson                  thrpt   10  139772.275      8854.369  ops/s
BenchmarkCollectSingleValue.benchmarkFastjsonWithJsonSurfer    thrpt   10  699176.961      23396.619  ops/s
BenchmarkCollectSingleValue.benchmarkGson                      thrpt   10  139394.358      6019.764  ops/s
BenchmarkCollectSingleValue.benchmarkGsonWithJsonSurfer        thrpt   10  632155.657      15484.499  ops/s
BenchmarkCollectSingleValue.benchmarkJackson                   thrpt   10  160545.079      7006.525  ops/s
BenchmarkCollectSingleValue.benchmarkJacksonWithJsonSurfer     thrpt   10  451870.586      13132.576  ops/s
BenchmarkCollectSingleValue.benchmarkJsonSimpleWithJsonSurfer  thrpt   10  155094.948      4457.502  ops/s
```

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