FASTJSON 2.0 yes FASTJSON Important upgrade of the project , The goal is to provide a high-performance platform for the next decade JSON library , The same set of API Support JSON/JSONB Two protocols ,JSONPath First class citizen , Support full resolution and partial resolution , Support Java Server side 、 client Android、 Big data scenario .

• FASJTONS2 Code https://github.com/alibaba/fastjson2/releases/tag/2.0.1

• JSONB Format document https://github.com/alibaba/fastjson2/wiki/jsonb_format_cn

• FASTJSON 2 Performance has been greatly improved , See here for specific performance data https://github.com/alibaba/fastjson2/wiki/fastjson_benchmark

2. Prepare before use

2.1 Maven rely on

stay fastjson 2.0 in ,groupId and 1.x Dissimilarity , yes com.alibaba.fastjson2

<dependency>
 <groupId>com.alibaba.fastjson2</groupId>
 <artifactId>fastjson2</artifactId>
 <version>2.0.1</version>
</dependency>

https://repo1.maven.org/maven2/com/alibaba/fastjson2/fastjson2/

2.2

If you used fastjson 1.2.x edition , Compatible packages can be used , Compatibility packages do not guarantee 100% compatible , Please test carefully to verify , If you find any problems, please give feedback in time .

<dependency>
 <groupId>com.alibaba</groupId>
 <artifactId>fastjson</artifactId>
 <version>2.0.1</version>
</dependency>

2.2 Common classes and methods

stay fastjson 2.0 in ,package and 1.x Dissimilarity , yes com.alibaba.fastjson2. If you used fastjson1, In most cases, just change the package name directly .

package com.alibaba.fastjson2;

class JSON {
    //  Parse a string into JSONObject
    static JSONObject parseObject(String str);
    
    //  Parse a string into JSONArray
    static JSONArray parseArray(String str);
    
    //  Parse a string into Java object 
    static T parseObject(byte[] utf8Bytes, Class<T> objectClass);

    //  take Java Object is output as a string 
    static String toJSONString(Object object);
    
    //  take Java Object output to UT8 Coded byte[]
    static byte[] toJSONBytes(Object object);
}

class JSONB {
    //  take jsonb Format byte[] It can be interpreted as Java object 
    static T parseObject(byte[] jsonbBytes, Class<T> objectClass);
    
    //  take Java Object output to jsonb Format byte[]
    static byte[] toBytes(Object object);
}

class JSONObject {
    Object get(String key);
    int getIntValue(String key);
    Integer getInteger(String key);
    long getLongValue(String key);
    Long getLong(String key);
    T getObject(String key, Class<T> objectClass);
    
    //  take JSONObject Object to Java object 
    T toJavaObject(Class<T> objectClass);
}

class JSONArray {
    Object get(int index);
    int getIntValue(int index);
    Integer getInteger(int index);
    long getLongValue(int index);
    Long getLong(int index);
    T getObject(int index, Class<T> objectClass);
}

class JSONPath {
    //  structure JSONPath
    static JSONPath of(String path);

    //  according to path Directly parse the input , Will partially analyze and optimize , Will not resolve all 
    Object extract(JSONReader jsonReader);
    
    //  according to path Evaluate objects 
    Object eval(Object rootObject);
}

class JSONReader {
    //  Construction is based on String Input JSONReader
    static JSONReader of(String str);
    
    //  Construction is based on ut8 code byte Array input JSONReader
    static JSONReader of(byte[] utf8Bytes);
    
    //  Construction is based on char[] Input JSONReader
    static JSONReader of(char[] chars);
    
    //  Construction is based on json Format byte Array input JSONReader
    static JSONReader ofJSONB(byte[] jsonbBytes)
}

3. Read JSON object

String str = "{\"id\":123}";
JSONObject jsonObject = JSON.parseObject(str);
int id = jsonObject.getIntValue("id");
String str = "[\"id\", 123]";
JSONArray jsonArray = JSON.parseArray(str);
String name = jsonArray.getString(0);
int id = jsonArray.getIntValue(1);

4. take JavaBean Object to generate JSON

4.1 take JavaBean Object to generate JSON Format string

class Product {
 public int id;
 public String name;
}

Product product = new Product();
product.id = 1001;
product.name = "DataWorks";

JSON.toJSONString(product);

//  The following results are generated 
{
 "id" : 1001,
 "name" : "DataWorks"
}

JSON.toJSONString(product, JSONWriter.Feature.BeanToArray);
//  The following results are generated 
[123, "DataWorks"]

4.2 take JavaBean Object to generate UTF8 Coded byte[]

Product product = ...;
byte[] utf8JSONBytes = JSON.toJSONBytes(product);

4.3 take JavaBean Object to generate JSONB Format byte[]

Product product = ...;
byte[] jsonbBytes = JSONB.toBytes(product);

byte[] jsonbBytes = JSONB.toBytes(product, JSONWriter.Feature.BeanToArray);

5. Read JavaBean

5.1 Read the string as JavaBean

String str = "{\"id\":123}";
Product product = JSON.parseObject(str, Product.class);

5.2 take UTF8 Coded byte[] Read into JavaBean

byte[] utf8Bytes = "{\"id\":123}".getBytes(StandardCharsets.UTF_8);
Product product = JSON.parseObject(utf8Bytes, Product.class);

5.3 take JSONB The data is read as JavaBean

byte[] jsonbBytes = ...
Product product = JSONB.parseObject(jsonbBytes, Product.class);

Product product = JSONB.parseObject(jsonbBytes, Product.class, JSONReader.Feature.SupportBeanArrayMapping);

6. Use JSONPath

6.1 Use JSONPath Partial read data

String str = ...;

JSONPath path = JSONPath.of("$.id"); //  Caching and reuse can improve performance 

JSONReader parser = JSONReader.of(str);
Object result = path.extract(parser);

6.2 Use JSONPath Read part utf8Bytes The data of

byte[] utf8Bytes = ...;

JSONPath path = JSONPath.of("$.id"); //  Caching and reuse can improve performance 

JSONReader parser = JSONReader.of(utf8Bytes);
Object result = path.extract(parser);

6.3 Use JSONPath Read part jsonbBytes The data of

byte[] jsonbBytes = ...;

JSONPath path = JSONPath.of("$.id"); //  Caching and reuse can improve performance 

JSONReader parser = JSONReader.ofJSONB(jsonbBytes); //  Be careful , It's using ofJSONB Method 
Object result = path.extract(parser);

source ：https://github.com/alibaba/fastjson2/releases

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