介绍4款json的java类库及其性能测试

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

一、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);
    }

二、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;
    }

三、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);
    }

四、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>1.1.35</version>
        </dependency>

示例：

    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);
    }

五、性能测试

1、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

2、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

3、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。

4、测试用例

1）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 + "]";
    }

}

2）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);
    }
}

3）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);
        }
    }

}

4）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);
        }
    }
}