Java JSON 类库: Json-lib, Gson, Jackson, FastJson

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:

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

示例:


public static String bean2Json(Object obj){

    return JSON.toJSONString(obj);

}

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:

<dependency>
<groupId>net.sf.json-lib</groupId>
<artifactId>json-lib</artifactId>
<version>2.4</version>
<classifier>jdk15</classifier>
</dependency>

示例:

/**
* 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> T json2Bean(String jsonStr,Class<T> objClass){
    return (T)JSONObject.toBean(JSONObject.fromObject(jsonStr), objClass);
}

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:

<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.2.4</version>
</dependency>

示例:

public static String bean2Json(Object obj){
    Gson gson = new GsonBuilder().create();
    return gson.toJson(obj);
}
public static <T> T json2Bean(String jsonStr,Class<T> 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;
}

Jackson

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

maven依赖:

<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-mapper-asl</artifactId>
<version>1.9.13</version>
</dependency>

示例:

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> T json2Bean(String jsonStr, Class<T> objClass)
throws JsonParseException, JsonMappingException, IOException {
    ObjectMapper mapper = new ObjectMapper();
    return mapper.readValue(jsonStr, objClass);
}

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<Person> 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

public class Person {
    private String name;
    private FullName fullName;
    private int age;
    private Date birthday;
    private List<String> hobbies;
    private Map<String, String> clothes;
    private List<Person> 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 + "]";
    }
}

Json-lib、Gson、Jackson、FastJson类库:

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> T json2Bean(String jsonStr,Class<T> objClass){
        return (T)JSONObject.toBean(JSONObject.fromObject(jsonStr), objClass);
    }
}
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> T json2Bean(String jsonStr,Class<T> 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;
    }
}
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> T json2Bean(String jsonStr, Class<T> objClass)
    throws JsonParseException, JsonMappingException, IOException {
        return mapper.readValue(jsonStr, objClass);
    }
}
public class FastJsonUtil {
    public static String bean2Json(Object obj){
        return JSON.toJSONString(obj);
    }
    public static <T> T json2Bean(String jsonStr,Class<T> objClass){
        return JSON.parseObject(jsonStr, objClass);
    }
}

Java对象序列化为Json字符串测试类:

public class TestBean2Json {
    private Person p;
    private Person createAPerson(String name,List<Person> friends) {
        Person newPerson=new Person();
        newPerson.setName(name);
        newPerson.setFullName(new FullName("xxx_first", "xxx_middle", "xxx_last"));
        newPerson.setAge(24);
        List<String> hobbies=new ArrayList<String>();
        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<Person> friends=new ArrayList<Person>();
        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);
        }
    }
}

Json字符串反序列化为Java对象测试类:

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);
    }
}
}

参考: http://www.json.org/json-zh.html

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

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