Java的4種Json類庫介紹

阿新 • • 發佈：2019-01-10

JSON(JavaScript Object Notation) 是一種輕量級的資料交換格式。易於人閱讀和編寫。同時也易於機器解析和生成。它基於JavaScript Programming Language, Standard ECMA-262 3rd Edition - December 1999的一個子集。 JSON採用完全獨立於語言的文字格式，這些特性使JSON成為理想的資料交換語言。

下面介紹四款處理json的java類庫：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. 官網：

http://json-lib.sourceforge.net/

maven依賴配置：

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

示例：

    /**
     * 將物件序列化成json字串
     * @param obj
     * @return
     */
    public static String bean2Json(Object obj){
        JSONObject jsonObject=JSONObject.fromObject(obj);
        return jsonObject.toString();
    }
    
    /**
     * 將json字串反序列化為物件
     * @param jsonStr
     * @param objClass 反序列化為該類的物件
     * @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.

maven依賴：

        <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);
    }
    
    /**
     * 把混亂的json字串整理成縮排的json字串
     * @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)。官網：http://jackson.codehaus.org/Home

maven依賴：

<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

maven依賴配置：

        <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、效能測試

1、Java物件序列化為Json字串：

執行100 0000次轉換，各個類庫的耗時如下：（以秒為單位）

Gson	48.891s
Json-lib	311.446s
Jackson	19.439s
FastJson	21.706

2、Json字串反序列化為Java物件

執行100 0000次轉換，各個類庫的耗時如下：（以秒為單位）

Gson	39.280s
Json-lib	使用該類庫的方法進行轉換時（測試程式碼見下面），丟擲異常。其原因是Person類的屬性：List<Person> friends，其List中的物件不是Person型別的物件，而是net.sf.ezmorph.bean.MorphDynaBean型別的物件。說明，Json-lib對巢狀的自定義類支援的很差，或許是我寫的方法有問題。
Jackson	26.427s
FastJson	40.556

3、總結：

Java Bean序列化為Json，效能：Jackson > FastJson > Gson > Json-lib。這4中類庫的序列化結構都正確。

Json字串反序列化為Java Bean時，效能：Jackson > Gson > FastJson >Json-lib。並且Jackson、Gson、FastJson可以很好的支援複雜的巢狀結構定義的類，而Json-lib對於複製的反序列化會出錯。

Jackson、FastJson、Gson類庫各有優點，各有自己的專長，都具有很高的可用性。

4、測試用例

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;
    
　　//構造方法、getter setter 方法，略
 　　
    @Override
    public String toString() {
        return "[firstName=" + firstName + ", middleName="
                + middleName + ", lastName=" + lastName + "]";
    }
    
}

2）Json-lib、Gson、Jackson、FastJson類庫：

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物件序列化為Json字串測試類：

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("籃球");
        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("陳小二",null));
         p=createAPerson("邵同學",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字串反序列化為Java物件測試類：

public class TestJson2Bean {
    private String jsonStr;
    
    @Before
    public void init(){
         jsonStr="{\"name\":\"邵同學\",\"fullName\":{\"firstName\":\"xxx_first\",\"middleName\":\"xxx_middle\",\"lastName\":\"xxx_last\"},\"age\":24,\"birthday\":null,\"hobbies\":[\"籃球\",\"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\":[\"籃球\",\"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\":[\"籃球\",\"游泳\",\"coding\"],\"clothes\":{\"shoes\":\"安踏\",\"trousers\":\"adidas\",\"coat\":\"Nike\"},\"friends\":null},{\"name\":\"陳小二\",\"fullName\":{\"firstName\":\"xxx_first\",\"middleName\":\"xxx_middle\",\"lastName\":\"xxx_last\"},\"age\":24,\"birthday\":null,\"hobbies\":[\"籃球\",\"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);
        }
    }
}

http://www.cnblogs.com/hoojo/archive/2011/04/22/2024628.html

http://www.cnblogs.com/windlaughing/p/3241776.html

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Java的4種Json類庫介紹

一、Json-lib

二、Gson

三、Jackson

四、FastJson

五、效能測試

歡迎關注公眾號：

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Java的4種Json類庫介紹

一、Json-lib

二、Gson

三、Jackson

四、FastJson

五、效能測試

歡迎關注公眾號：

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