4款json的java类库, FastJson

JSON(JavaScript Object Notation) 是一种轻量级的数据交换格式。易于人阅读和编写。同时也易于机器解析和生成。它基于JavaScript Programming Language, Standard ECMA-262 3rd Edition - December 1999的一个子集。 JSON采用完全独立于语言的文本格式，这些特性使JSON成为理想的数据交换语言。

下面介绍四款处理json的java类库: Json-lib、Gson、Jackson、Fastjson

FastJson

Fastjson是一个Java语言编写的JSON处理器,由阿里巴巴公司开发。网址: https://github.com/alibaba/fastjson

maven依赖配置:

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<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.79</version>
</dependency>

示例:

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public static String bean2Json(Object obj){

return JSON.toJSONString(obj);

}

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VO vo = JSON.parseObject("...", VO.class);```
  
  

Json-lib

JSON-lib is a java library for transforming beans, maps, collections, java arrays and XML to JSON and back again to beans and DynaBeans. 官网: http://json-lib.sourceforge.net/

maven依赖配置:

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net.sf.json-lib

json-lib

2.4

jdk15

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示例:

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/**

将对象序列化成json字符串
@param obj
@return

public static String bean2Json(Object obj){

JSONObject jsonObject=JSONObject.fromObject(obj);

return jsonObject.toString();

}

/**

将json字符串反序列化为对象
@param jsonStr
@param objClass 反序列化为该类的对象
@return

@SuppressWarnings(“unchecked”)

public static T json2Bean(String jsonStr,Class objClass){

return (T)JSONObject.toBean(JSONObject.fromObject(jsonStr), objClass);

}

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Gson

Gson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object. Gson can work with arbitrary Java objects including pre-existing objects that you do not have source-code of.

官网: https://code.google.com/p/google-gson/

maven依赖:

com.google.code.gson

gson

2.2.4

示例:

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public static String bean2Json(Object obj){

Gson gson = new GsonBuilder().create();

return gson.toJson(obj);

}

public static T json2Bean(String jsonStr,Class objClass){

Gson gson = new GsonBuilder().create();

return gson.fromJson(jsonStr, objClass);

}

/**

把混乱的json字符串整理成缩进的json字符串
@param uglyJsonStr
@return

public static String jsonFormatter(String uglyJsonStr){

Gson gson = new GsonBuilder().setPrettyPrinting().create();

JsonParser jp = new JsonParser();

JsonElement je = jp.parse(uglyJsonStr);

String prettyJsonString = gson.toJson(je);

return prettyJsonString;

}

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Jackson

Jackson is a high-performance JSON processor (parser, generator)。官网: http://jackson.codehaus.org/Home

maven依赖:

org.codehaus.jackson

jackson-mapper-asl

1.9.13

示例:

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public static String bean2Json(Object obj) throws IOException {

ObjectMapper mapper = new ObjectMapper();

StringWriter sw = new StringWriter();

JsonGenerator gen = new JsonFactory().createJsonGenerator(sw);

mapper.writeValue(gen, obj);

gen.close();

return sw.toString();

}

public static T json2Bean(String jsonStr, Class objClass)

throws JsonParseException, JsonMappingException, IOException {

ObjectMapper mapper = new ObjectMapper();

return mapper.readValue(jsonStr, objClass);

}

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五、性能测试

Java对象序列化为Json字符串:

执行100 0000次转换，各个类库的耗时如下: (以秒为单位)

Gson 48.891s

Json-lib 311.446s

Jackson 19.439s

FastJson 21.706

Json字符串反序列化为Java对象

执行100 0000次转换，各个类库的耗时如下: (以秒为单位)

Gson 39.280s

Json-lib 使用该类库的方法进行转换时 (测试代码见下面) ，抛出异常。其原因是Person类的属性: List friends，其List中的对象不是Person类型的对象，而是net.sf.ezmorph.bean.MorphDynaBean类型的对象。说明，Json-lib对嵌套的自定义类支持的很差，或许是我写的方法有问题。

Jackson 26.427s

FastJson 40.556

总结:

Java Bean序列化为Json，性能: Jackson > FastJson > Gson > Json-lib。这4中类库的序列化结构都正确。

Json字符串反序列化为Java Bean时，性能: Jackson > Gson > FastJson >Json-lib。并且Jackson、Gson、FastJson可以很好的支持复杂的嵌套结构定义的类，而Json-lib对于复制的反序列化会出错。

Jackson、FastJson、Gson类库各有优点，各有自己的专长，都具有很高的可用性。

测试用例

Java Bean

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public class Person {

private String name;

private FullName fullName;

private int age;

private Date birthday;

private List hobbies;

private Map<String, String> clothes;

private List friends;

//getter setter 方法。略

@Override

public String toString() {

String str= “Person [name=” + name + “, fullName=” + fullName + “, age=”

age + “, birthday=” + birthday + “, hobbies=” + hobbies
“, clothes=” + clothes + “]\n”;

if(friends!=null){

str+="Friends:\n”;

for (Person f : friends) {

str+=”\t"+f;

}

return str;

}

class FullName {

private String firstName;

private String middleName;

private String lastName;

//构造方法、getter setter 方法，略

@Override

public String toString() {

return “[firstName=” + firstName + “, middleName=”

middleName + “, lastName=” + lastName + “]";

}

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Json-lib、Gson、Jackson、FastJson类库:

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import net.sf.json.JSONObject;

public class JsonObjectUtil {

public static String bean2Json(Object obj){

JSONObject jsonObject=JSONObject.fromObject(obj);

return jsonObject.toString();

}

@SuppressWarnings(“unchecked”)

public static T json2Bean(String jsonStr,Class objClass){

return (T)JSONObject.toBean(JSONObject.fromObject(jsonStr), objClass);

}

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import com.google.gson.Gson;

import com.google.gson.GsonBuilder;

import com.google.gson.JsonElement;

import com.google.gson.JsonParser;

public class GsonUtil {

private static Gson gson = new GsonBuilder().create();

public static String bean2Json(Object obj){

return gson.toJson(obj);

}

public static T json2Bean(String jsonStr,Class objClass){

return gson.fromJson(jsonStr, objClass);

}

public static String jsonFormatter(String uglyJsonStr){

Gson gson = new GsonBuilder().setPrettyPrinting().create();

JsonParser jp = new JsonParser();

JsonElement je = jp.parse(uglyJsonStr);

String prettyJsonString = gson.toJson(je);

return prettyJsonString;

}

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import java.io.IOException;

import java.io.StringWriter;

import org.codehaus.jackson.JsonFactory;

import org.codehaus.jackson.JsonGenerator;

import org.codehaus.jackson.JsonParseException;

import org.codehaus.jackson.map.JsonMappingException;

import org.codehaus.jackson.map.ObjectMapper;

public class JacksonUtil {

private static ObjectMapper mapper = new ObjectMapper();

public static String bean2Json(Object obj) throws IOException {

StringWriter sw = new StringWriter();

JsonGenerator gen = new JsonFactory().createJsonGenerator(sw);

mapper.writeValue(gen, obj);

gen.close();

return sw.toString();

}

public static T json2Bean(String jsonStr, Class objClass)

throws JsonParseException, JsonMappingException, IOException {

return mapper.readValue(jsonStr, objClass);

}

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public class FastJsonUtil {

public static String bean2Json(Object obj){

return JSON.toJSONString(obj);

}

public static T json2Bean(String jsonStr,Class objClass){

return JSON.parseObject(jsonStr, objClass);

}

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Java对象序列化为Json字符串测试类:

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public class TestBean2Json {

private Person p;

private Person createAPerson(String name,List friends) {

Person newPerson=new Person();

newPerson.setName(name);

newPerson.setFullName(new FullName(“xxx_first”, “xxx_middle”, “xxx_last”));

newPerson.setAge(24);

List hobbies=new ArrayList();

hobbies.add(“篮球”);

hobbies.add(“游泳”);

hobbies.add(“coding”);

newPerson.setHobbies(hobbies);

Map<String,String> clothes=new HashMap<String, String>();

clothes.put(“coat”, “Nike”);

clothes.put(“trousers”, “adidas”);

clothes.put(“shoes”, “安踏”);

newPerson.setClothes(clothes);

newPerson.setFriends(friends);

return newPerson;

}

@Before

public void init(){

List friends=new ArrayList();

friends.add(createAPerson(“小明”,null));

friends.add(createAPerson(“Tony”,null));

friends.add(createAPerson(“陈小二”,null));

p=createAPerson(“邵同学”,friends);

}

// @Test

public void testGsonBean2Json(){

System.out.println(GsonUtil.bean2Json(p));

for (int i = 0; i < 1000000; i++) {

GsonUtil.bean2Json(p);

}

//@Test

public void testJsonObjectBean2Json(){

System.out.println(JsonlibUtil.bean2Json(p));

for (int i = 0; i < 1000000; i++) {

JsonlibUtil.bean2Json(p);

}

// @Test

public void testJacksonBean2Json() throws Exception{

System.out.println(JacksonUtil.bean2Json(p));

for (int i = 0; i < 1000000; i++) {

JacksonUtil.bean2Json(p);

}

@Test

public void testFastJsonBean2Json() throws Exception{

System.out.println(FastJsonUtil.bean2Json(p));

for (int i = 0; i < 1000000; i++) {

FastJsonUtil.bean2Json(p);

}

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Json字符串反序列化为Java对象测试类:

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public class TestJson2Bean {

private String jsonStr;

@Before

public void init(){

jsonStr=”{"name":"邵同学","fullName":{"firstName":"xxx_first","middleName":"xxx_middle","lastName":"xxx_last"},"age":24,"birthday":null,"hobbies":["篮球","游泳","coding"],"clothes":{"shoes":"安踏","trousers":"adidas","coat":"Nike"},"friends":[{"name":"小明","fullName":{"firstName":"xxx_first","middleName":"xxx_middle","lastName":"xxx_last"},"age":24,"birthday":null,"hobbies":["篮球","游泳","coding"],"clothes":{"shoes":"安踏","trousers":"adidas","coat":"Nike"},"friends":null},{"name":"Tony","fullName":{"firstName":"xxx_first","middleName":"xxx_middle","lastName":"xxx_last"},"age":24,"birthday":null,"hobbies":["篮球","游泳","coding"],"clothes":{"shoes":"安踏","trousers":"adidas","coat":"Nike"},"friends":null},{"name":"陈小二","fullName":{"firstName":"xxx_first","middleName":"xxx_middle","lastName":"xxx_last"},"age":24,"birthday":null,"hobbies":["篮球","游泳","coding"],"clothes":{"shoes":"安踏","trousers":"adidas","coat":"Nike"},"friends":null}]}";

}

// @Test

public void testGsonjson2Bean() throws Exception{

Person pp=GsonUtil.json2Bean(jsonStr, Person.class);

System.out.println(pp);

for (int i = 0; i < 1000000; i++) {

GsonUtil.json2Bean(jsonStr, Person.class);

}

// @Test

public void testJsonlibJson2Bean() throws Exception{

Person pp=JsonlibUtil.json2Bean(jsonStr, Person.class);

System.out.println(pp);

for (int i = 0; i < 1000000; i++) {

JsonlibUtil.json2Bean(jsonStr, Person.class);

}

// @Test

public void testJacksonJson2Bean() throws Exception{

Person pp=JacksonUtil.json2Bean(jsonStr, Person.class);

System.out.println(pp);

for (int i = 0; i < 1000000; i++) {

JacksonUtil.json2Bean(jsonStr, Person.class);

}

@Test

public void testFastJsonJson2Bean() throws Exception{

Person pp=FastJsonUtil.json2Bean(jsonStr, Person.class);

System.out.println(pp);

for (int i = 0; i < 1000000; i++) {

FastJsonUtil.json2Bean(jsonStr, Person.class);

}

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参考: http://www.json.org/json-zh.html

http://www.oschina.net/code/snippet_1156226_26432

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