1. What is fastjson?
fastjson is Alibaba's open source JSON parsing library. It can parse strings in JSON format, and supports serialization of Java Beans to JSON strings, as well as deserialization from JSON strings to JavaBeans.
Fastjson usage scenarios
Fastjson has been widely used in various scenarios, including cache storage, RPC communication, MQ communication, network protocol communication, Android client, Ajax server handler, etc.
2. Advantages of fastjson
2.1 Fast
Compared with other JSON libraries, fastjson is fast. Since fastjson released version 1.1.x in 2011, its performance has never been surpassed by other JSON libraries implemented in Java.
2.2 Widely used
Fastjson is widely used in Alibaba and deployed on tens of thousands of servers. Fastjson is widely accepted in the industry. In 2012, it was selected as one of the most popular domestic open source software by Open Source China.
2.3 Complete testing
fastjson has a lot of testcases. In version 1.2.11, there are more than 3321 testcases. Regression testing is performed on each release to ensure consistent quality.
2.4 Easy to use
The API of fastjson is very concise.
String text = JSON.toJSONString(obj); //序列化
VO vo = JSON.parseObject("{...}", VO.class); //反序列化 2.5 Fully functional
Supports generics, supports stream processing of very large text, supports enumeration, supports serialization and deserialization extensions.
The following example tests two important methods, JSON.toJSONString and JSON.parseObject:
Fruit entity class:
1 package com.led.daorumysql; 2 3 /** 4 * Define fruit entity class 5 * @author 86157 6 * 7 */ 8 public class Fruit { 9 10 // Fruit name 11 private String name; 12 // Fruit origin 13 private String origin; 14 // fruit price 15 private Integer price; 16 17 public String getName() { 18 return name; 19 } 20 public void setName(String name) { 21 this.name = name; 22 } 23 public String getOrigin() { 24 return origin; 25 } 26 public void setOrigin(String origin) { 27 this.origin = origin; 28 } 29 public Integer getPrice() { 30 return price; 31 } 32 public void setPrice(Integer price) { 33 this.price = price; 34 } 35 @Override 36 public String toString() { 37 return "Fruit [name=" + name + ", origin=" + origin + ", price=" + price + "]"; 38 } 39 40 public Fruit(String name, String origin, Integer price) { 41 super(); 42 this.name = name; 43 this.origin = origin; 44 this.price = price; 45 } 46 47 public Fruit() { 48 super(); 49 } 50 51 52 53 54 }
Main class:
1 package com.led.daorumysql; 2 3 import java.util.ArrayList; 4 import java.util.List; 5 6 import com.alibaba.fastjson.JSON; 7 8 /** 9 * FastJSON test class 10 * @author 86157 11 * 12 */ 13 public class FastJSONTest { 14 15 public static void main(String[] args) { 16 // Instantiate Fruit class 17 Fruit fruitOne = newFruit("apple", "America", 13 ); 18 Fruit fruitTwo = new Fruit("orange", "China", 15 ); 19 // Create fruitList object 20 List<Fruit> fruitList = new ArrayList<Fruit> ( ); 21 fruitList.add(fruitOne); 22 fruitList.add(fruitTwo); 23 24 // Convert the java object (Fruit) into a json string 25 System.out.println("========== Convert java object (Fruit) to json string ==========" ); 26 String fruitOne_jsonString = JSON.toJSONString(fruitOne); 27 System.out.println("fruitOne_jsonString: " + fruitOne_jsonString); 28 System.out.println(); 29 30 // Convert json string to java object (Fruit) 31 System.out.println("==== ===== Convert json string to java object (Fruit) ==========" ); 32 Fruit fruitOne_parseObject = JSON.parseObject(fruitOne_jsonString, Fruit. class ); 33 System.out. println("fruit object: " + fruitOne_parseObject); 34 System.out.println("fruit name: " + fruitOne_parseObject.getName()); 35 System.out.println("fruit origin: " + fruitOne_parseObject. getOrigin ());36 System.out.println("fruit price: " + fruitOne_parseObject.getPrice()); 37 System.out.println(); 38 39 // Convert java object (fruitList) into json string 40 System.out.println ("========Convert java object (fruitList) to json string========" ); 41 String fruitList_jsonString = JSON.toJSONString(fruitList); 42 System.out.println ("fruitList_jsonString: " + fruitList_jsonString); 43 System.out.println(); 44 45 // Convert json string to java object (fruitList) 46 System.out.println("========== Convert json string to java object (fruitList)========"); 47 List<Fruit> parseArray = JSON.parseArray(fruitList_jsonString, Fruit.class); 48 System.out.println("fruitOne object: " + parseArray.get(0).toString()); 49 System.out.println("fruitTwo object: " + parseArray.get(1).toString()); 50 System.out.println("fruitTwo object name: " + parseArray.get(1).getName()); 51 52 } 53 }
Console output:
1 ========= Convert java object (Fruit) to json string =========== 2 fruitOne_jsonString: {"name":"apple","origin":"America ","price":13 } 3 4 =========Convert json string to java object (Fruit) =========== 5 fruit object: Fruit [name=apple , origin=America, price=13 ] 6 fruit name: apple 7 fruit origin: America 8 fruit price: 13 9 10 ========= Convert java object (fruitList) to json string==== ==== 11 fruitList_jsonString: [{"name":"apple","origin":"America","price":13},{"name":"orange","origin":"China"," price":15 }] 12 13 ========= Convert json string to java object (fruitList) ======== 14 fruitOne object: Fruit [name=apple, origin=America, price=13] 15 fruitTwo object: Fruit [name=orange, origin=China, price=15] 16 fruitTwo object name: orange
Notice:
A constructor must be created in the entity class, otherwise parseObject will report the following error:
Exception in thread "main" com.alibaba.fastjson.JSONException: default constructor not found. class com.led.daorumysql.Fruit at com.alibaba.fastjson.util.JavaBeanInfo.build(JavaBeanInfo.java:197) at com.alibaba.fastjson.parser.ParserConfig.createJavaBeanDeserializer(ParserConfig.java:465) at com.alibaba.fastjson.parser.ParserConfig.getDeserializer(ParserConfig.java:412) at com.alibaba.fastjson.parser.ParserConfig.getDeserializer(ParserConfig.java:324) at com.alibaba.fastjson.parser.DefaultJSONParser.parseObject(DefaultJSONParser.java:594) at com.alibaba.fastjson.parser.DefaultJSONParser.parseObject(DefaultJSONParser.java:569) at com.alibaba.fastjson.JSON.parseObject(JSON.java:257) at com.alibaba.fastjson.JSON.parseObject(JSON.java:227) at com.alibaba.fastjson.JSON.parseObject(JSON.java:186) at com.alibaba.fastjson.JSON.parseObject(JSON.java:310) at com.led.daorumysql.FastJSONTest.main(FastJSONTest.java:27)