com.alibaba的fastjson简介

2022-07-13 22:28:21

fastjson简介

Fastjson是一个Java语言编写的高性能功能完善的JSON库。它采用一种“假定有序快速匹配”的算法，把JSON Parse的性能提升到极致，是目前Java语言中最快的JSON库。Fastjson接口简单易用，已经被广泛使用在缓存序列化、协议交互、Web输出、Android客户端等多种应用场景

1.前言

1.1.FastJson的介绍:

JSON协议使用方便，越来越流行,JSON的处理器有很多,这里我介绍一下FastJson,FastJson是阿里的开源框架,被不少企业使用,是一个极其优秀的Json框架,Github地址: FastJson

1.2.FastJson的特点:

1.FastJson数度快,无论序列化和反序列化,都是当之无愧的fast
2.功能强大(支持普通JDK类包括任意Java Bean Class、Collection、Map、Date或enum)
3.零依赖(没有依赖其它任何类库)

1.3.FastJson的简单说明:

FastJson对于json格式字符串的解析主要用到了下面三个类：
1.JSON：fastJson的解析器，用于JSON格式字符串与JSON对象及javaBean之间的转换
2.JSONObject：fastJson提供的json对象
3.JSONArray：fastJson提供json数组对象

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2.FastJson的用法

首先定义三个json格式的字符串

//json字符串-简单对象型

private static final String  JSON_OBJ_STR = "{\"studentName\":\"lily\",\"studentAge\":12}";

//json字符串-数组类型

private static final String  JSON_ARRAY_STR = "[{\"studentName\":\"lily\",\"studentAge\":12},{\"studentName\":\"lucy\",\"studentAge\":15}]";

//复杂格式json字符串

private static final String  COMPLEX_JSON_STR = "{\"teacherName\":\"crystall\",\"teacherAge\":27,\"course\":{\"courseName\":\"english\",\"code\":1270},\"students\":[{\"studentName\":\"lily\",\"studentAge\":12},{\"studentName\":\"lucy\",\"studentAge\":15}]}";

2.1.JSON格式字符串与JSON对象之间的转换

2.1.1.json字符串-简单对象型与JSONObject之间的转换

/**

 * json字符串-简单对象型到JSONObject的转换

 */

@Test

public void testJSONStrToJSONObject() {

    JSONObject jsonObject = JSONObject.parseObject(JSON_OBJ_STR);

    System.out.println("studentName:  " + jsonObject.getString("studentName") + ":" + "  studentAge:  "

            + jsonObject.getInteger("studentAge"));

}

/**

 * JSONObject到json字符串-简单对象型的转换

 */

@Test

public void testJSONObjectToJSONStr() {

    //已知JSONObject,目标要转换为json字符串

    JSONObject jsonObject = JSONObject.parseObject(JSON_OBJ_STR);

    // 第一种方式

    String jsonString = JSONObject.toJSONString(jsonObject);

    // 第二种方式

    //String jsonString = jsonObject.toJSONString();

    System.out.println(jsonString);

}

2.1.2.json字符串(数组类型)与JSONArray之间的转换

/**

 * json字符串-数组类型到JSONArray的转换

 */

@Test

public void testJSONStrToJSONArray() {

    JSONArray jsonArray = JSONArray.parseArray(JSON_ARRAY_STR);

    //遍历方式1

    int size = jsonArray.size();

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

        JSONObject jsonObject = jsonArray.getJSONObject(i);

        System.out.println("studentName:  " + jsonObject.getString("studentName") + ":" + "  studentAge:  "

                + jsonObject.getInteger("studentAge"));

    }

    //遍历方式2

    for (Object obj : jsonArray) {

        JSONObject jsonObject = (JSONObject) obj;

        System.out.println("studentName:  " + jsonObject.getString("studentName") + ":" + "  studentAge:  "

                + jsonObject.getInteger("studentAge"));

    }

}

/**

 * JSONArray到json字符串-数组类型的转换

 */

@Test

public void testJSONArrayToJSONStr() {

    //已知JSONArray,目标要转换为json字符串

    JSONArray jsonArray = JSONArray.parseArray(JSON_ARRAY_STR);

    //第一种方式

    String jsonString = JSONArray.toJSONString(jsonArray);

    // 第二种方式

    //String jsonString = jsonArray.toJSONString(jsonArray);

    System.out.println(jsonString);

}

2.1.3.复杂json格式字符串与JSONObject之间的转换

/**

 * 复杂json格式字符串到JSONObject的转换

 */

@Test

public void testComplexJSONStrToJSONObject() {

    JSONObject jsonObject = JSONObject.parseObject(COMPLEX_JSON_STR);

    String teacherName = jsonObject.getString("teacherName");

    Integer teacherAge = jsonObject.getInteger("teacherAge");

    System.out.println("teacherName:  " + teacherName + "   teacherAge:  " + teacherAge);

    JSONObject jsonObjectcourse = jsonObject.getJSONObject("course");

     //获取JSONObject中的数据

    String courseName = jsonObjectcourse.getString("courseName");

    Integer code = jsonObjectcourse.getInteger("code");

    System.out.println("courseName:  " + courseName + "   code:  " + code);

    JSONArray jsonArraystudents = jsonObject.getJSONArray("students");

    //遍历JSONArray

    for (Object object : jsonArraystudents) {

        JSONObject jsonObjectone = (JSONObject) object;

        String studentName = jsonObjectone.getString("studentName");

        Integer studentAge = jsonObjectone.getInteger("studentAge");

        System.out.println("studentName:  " + studentName + "   studentAge:  " + studentAge);

    }

}

/**

 * 复杂JSONObject到json格式字符串的转换

 */

@Test

public void testJSONObjectToComplexJSONStr() {

   //复杂JSONObject,目标要转换为json字符串

    JSONObject jsonObject = JSONObject.parseObject(COMPLEX_JSON_STR);

    //第一种方式

    //String jsonString = JSONObject.toJSONString(jsonObject);

    //第二种方式

    String jsonString = jsonObject.toJSONString();

    System.out.println(jsonString);

}

2.2.JSON格式字符串与javaBean之间的转换

2.2.1.json字符串-简单对象型与javaBean之间的转换

/**

 * json字符串-简单对象到JavaBean之间的转换

 */

@Test

public void testJSONStrToJavaBeanObj() {

    //第一种方式

    JSONObject jsonObject = JSONObject.parseObject(JSON_OBJ_STR);

    String studentName = jsonObject.getString("studentName");

    Integer studentAge = jsonObject.getInteger("studentAge");

    //Student student = new Student(studentName, studentAge);

    //第二种方式,使用TypeReference<T>类,由于其构造方法使用protected进行修饰,故创建其子类

    //Student student = JSONObject.parseObject(JSON_OBJ_STR, new TypeReference<Student>() {});

    //第三种方式,使用Gson的思想

    Student student = JSONObject.parseObject(JSON_OBJ_STR, Student.class);

    System.out.println(student);

}

/**

 * JavaBean到json字符串-简单对象的转换

 */

@Test

public void testJavaBeanObjToJSONStr() {

    Student student = new Student("lily", 12);

    String jsonString = JSONObject.toJSONString(student);

    System.out.println(jsonString);

}

2.2.2.json字符串-数组类型与javaBean之间的转换

/**

 * json字符串-数组类型到JavaBean_List的转换

 */

@Test

public void testJSONStrToJavaBeanList() {

    //第一种方式

    JSONArray jsonArray = JSONArray.parseArray(JSON_ARRAY_STR);

    //遍历JSONArray

    List<Student> students = new ArrayList<Student>();

    Student student = null;

    for (Object object : jsonArray) {

        JSONObject jsonObjectone = (JSONObject) object;

        String studentName = jsonObjectone.getString("studentName");

        Integer studentAge = jsonObjectone.getInteger("studentAge");

        student = new Student(studentName,studentAge);

        students.add(student);

    }

    System.out.println("students:  " + students);

    //第二种方式,使用TypeReference<T>类,由于其构造方法使用protected进行修饰,故创建其子类

    List<Student> studentList = JSONArray.parseObject(JSON_ARRAY_STR, new TypeReference<ArrayList<Student>>() {});

    System.out.println("studentList:  " + studentList);

    //第三种方式,使用Gson的思想

    List<Student> studentList1 = JSONArray.parseArray(JSON_ARRAY_STR, Student.class);

    System.out.println("studentList1:  " + studentList1);

}

/**

 * JavaBean_List到json字符串-数组类型的转换

 */

@Test

public void testJavaBeanListToJSONStr() {

    Student student = new Student("lily", 12);

    Student studenttwo = new Student("lucy", 15);

    List<Student> students = new ArrayList<Student>();

    students.add(student);

    students.add(studenttwo);

    String jsonString = JSONArray.toJSONString(students);

    System.out.println(jsonString);

}

2.2.3.复杂json格式字符串与与javaBean之间的转换

/**

 * 复杂json格式字符串到JavaBean_obj的转换

 */

@Test

public void testComplexJSONStrToJavaBean(){

    //第一种方式,使用TypeReference<T>类,由于其构造方法使用protected进行修饰,故创建其子类

    Teacher teacher = JSONObject.parseObject(COMPLEX_JSON_STR, new TypeReference<Teacher>() {});

    System.out.println(teacher);

    //第二种方式,使用Gson思想

    Teacher teacher1 = JSONObject.parseObject(COMPLEX_JSON_STR, Teacher.class);

    System.out.println(teacher1);

}

/**

 * 复杂JavaBean_obj到json格式字符串的转换

 */

@Test

public void testJavaBeanToComplexJSONStr(){

    //已知复杂JavaBean_obj

    Teacher teacher = JSONObject.parseObject(COMPLEX_JSON_STR, new TypeReference<Teacher>() {});

    String jsonString = JSONObject.toJSONString(teacher);

    System.out.println(jsonString);

}

2.3.javaBean与json对象间的之间的转换

2.3.1.简单javaBean与json对象之间的转换

/**

 * 简单JavaBean_obj到json对象的转换

 */

@Test

public void testJavaBeanToJSONObject(){

    //已知简单JavaBean_obj

    Student student = new Student("lily", 12);

    //方式一

    String jsonString = JSONObject.toJSONString(student);

    JSONObject jsonObject = JSONObject.parseObject(jsonString);

    System.out.println(jsonObject);

    //方式二

    JSONObject jsonObject1 = (JSONObject) JSONObject.toJSON(student);

    System.out.println(jsonObject1);

}

/**

 * 简单json对象到JavaBean_obj的转换

 */

@Test

public void testJSONObjectToJavaBean(){

    //已知简单json对象

    JSONObject jsonObject = JSONObject.parseObject(JSON_OBJ_STR);

    //第一种方式,使用TypeReference<T>类,由于其构造方法使用protected进行修饰,故创建其子类

    Student student = JSONObject.parseObject(jsonObject.toJSONString(), new TypeReference<Student>() {});

    System.out.println(student);

    //第二种方式,使用Gson的思想

    Student student1 = JSONObject.parseObject(jsonObject.toJSONString(), Student.class);

    System.out.println(student1);

}

2.3.2.JavaList与JsonArray之间的转换

/**

 * JavaList到JsonArray的转换

 */

@Test

public void testJavaListToJsonArray() {

    //已知JavaList

    Student student = new Student("lily", 12);

    Student studenttwo = new Student("lucy", 15);

    List<Student> students = new ArrayList<Student>();

    students.add(student);

    students.add(studenttwo);

    //方式一

    String jsonString = JSONArray.toJSONString(students);

    JSONArray jsonArray = JSONArray.parseArray(jsonString);

    System.out.println(jsonArray);

    //方式二

    JSONArray jsonArray1 = (JSONArray) JSONArray.toJSON(students);

    System.out.println(jsonArray1);

}

/**

 * JsonArray到JavaList的转换

 */

@Test

public void testJsonArrayToJavaList() {

    //已知JsonArray

    JSONArray jsonArray = JSONArray.parseArray(JSON_ARRAY_STR);

    //第一种方式,使用TypeReference<T>类,由于其构造方法使用protected进行修饰,故创建其子类

    ArrayList<Student> students = JSONArray.parseObject(jsonArray.toJSONString(),

            new TypeReference<ArrayList<Student>>() {});

    System.out.println(students);

    //第二种方式,使用Gson的思想

    List<Student> students1 = JSONArray.parseArray(jsonArray.toJSONString(), Student.class);

    System.out.println(students1);

}

2.3.3.复杂JavaBean_obj与json对象之间的转换

/**

 * 复杂JavaBean_obj到json对象的转换

 */

@Test

public void testComplexJavaBeanToJSONObject() {

    //已知复杂JavaBean_obj

    Student student = new Student("lily", 12);

    Student studenttwo = new Student("lucy", 15);

    List<Student> students = new ArrayList<Student>();

    students.add(student);

    students.add(studenttwo);

    Course course = new Course("english", 1270);

    Teacher teacher = new Teacher("crystall", 27, course, students);

    //方式一

    String jsonString = JSONObject.toJSONString(teacher);

    JSONObject jsonObject = JSONObject.parseObject(jsonString);

    System.out.println(jsonObject);

    //方式二

    JSONObject jsonObject1 = (JSONObject) JSONObject.toJSON(teacher);

    System.out.println(jsonObject1);

}

/**

 * 复杂json对象到JavaBean_obj的转换

 */

@Test

public void testComplexJSONObjectToJavaBean() {

    //已知复杂json对象

    JSONObject jsonObject = JSONObject.parseObject(COMPLEX_JSON_STR);

    //第一种方式,使用TypeReference<T>类,由于其构造方法使用protected进行修饰,故创建其子类

    Teacher teacher = JSONObject.parseObject(jsonObject.toJSONString(), new TypeReference<Teacher>() {});

    System.out.println(teacher);

    //第二种方式,使用Gson的思想

    Teacher teacher1 = JSONObject.parseObject(jsonObject.toJSONString(), Teacher.class);

    System.out.println(teacher1);

}

3.源码

本篇博客的源码都在我的Github上,FastJsonDemo,欢迎大家Fork and Star!

Maven引入

<groupId>com.alibaba</groupId>

<artifactId>fastjson</artifactId>

</dependency>

常用api

1. 将对象序列化成json字符串

String com.alibaba.fastjson.JSON.toJSONString(Object object)

2. 将json字符串反序列化成对象

<T> Project com.alibaba.fastjson.JSON.parseObject(String text, Class<T> clazz)

3. 将json字符串反序列化成JSON对象

JSONObject com.alibaba.fastjson.JSON.parseObject(String text)

4.根据key 得到json中的json数组

JSONArray com.alibaba.fastjson.JSONObject.getJSONArray(String key)

5. 根据下标拿到json数组的json对象

JSONObject com.alibaba.fastjson.JSONArray.getJSONObject(int index)

6.. 根据key拿到json的字符串值

String com.alibaba.fastjson.JSONObject.getString(String key)

7. 根据key拿到json的int值

int com.alibaba.fastjson.JSONObject.getIntValue(String key)

8. 根据key拿到json的boolean值

boolean com.alibaba.fastjson.JSONObject.getBooleanValue(String key)

实例说明

Project类

package com.json;

import java.util.List;

public class Project {

    String pjName;

    boolean waibao;

    public boolean isWaibao() {

        return waibao;

    }

    public void setWaibao(boolean waibao) {

        this.waibao = waibao;

    }

    List<Factory> l_factory;

    //List<Worker> worker;

    public String getPjName() {

        return pjName;

    }

    public void setPjName(String pjName) {

        this.pjName = pjName;

    }

    public List<Factory> getL_factory() {

        return l_factory;

    }

    public void setL_factory(List<Factory> l_factory) {

        this.l_factory = l_factory;

    }

}

Factory类

package com.json;

import java.util.List;

public class Factory {

    String fcName;

    List<Worker> l_worker;

    public String getFcName() {

        return fcName;

    }

    public void setFcName(String fcName) {

        this.fcName = fcName;

    }

    public List<Worker> getL_worker() {

        return l_worker;

    }

    public void setL_worker(List<Worker> l_worker) {

        this.l_worker = l_worker;

    }

}

Worker类

package com.json;

public class Worker {

    String name;

    String sex;

    int age;

    public int getAge() {

        return age;

    }

    public void setAge(int age) {

        this.age = age;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public String getSex() {

        return sex;

    }

    public void setSex(String sex) {

        this.sex = sex;

    }

}

测试类

package com.json;

import java.util.ArrayList;

import java.util.List;

import com.alibaba.fastjson.JSON;

import com.alibaba.fastjson.JSONArray;

import com.alibaba.fastjson.JSONObject;

public class TestFastJson {

    public static void main(String args[]) {

        TestFastJson tfj = new TestFastJson();

        Project prj = tfj.init();

        String json= tfj.getJsonString(prj);

        System.out.println("json="+json);

        //json={"l_factory":[{"fcName":"东软","l_worker":[{"age":30,"name":"乔佳飞","sex":"男"},{"age":25,"name":"李帅飞","sex":"女"}]},{"fcName":"亚信","l_worker":[{"age":26,"name":"王新峰","sex":"男"},{"age":0}]}],"pjName":"接口自动化","waibao":true}

        System.out.println("waibao="+tfj.getJsonValueObj(json, "waibao", Boolean.class));

        //waibao=true

        JSONArray array = (JSONArray) tfj.getJsonValueObj(json, "l_factory", JSONArray.class);

        System.out.println("array="+array.toString());

        //array=[{"fcName":"东软","l_worker":[{"sex":"男","name":"乔佳飞","age":30},{"sex":"女","name":"李帅飞","age":25}]},{"fcName":"亚信","l_worker":[{"sex":"男","name":"王新峰","age":26},{"age":0}]}]

        String jsonArr = tfj.getJsonArrayValue(array, 0, "fcName");

        System.out.println("fcName="+jsonArr);

        //fcName=东软

        JSONArray array2 = tfj.getJsonArrayValueIsArray(array, 0, "l_worker");

        System.out.println("array2="+array2.toString());

        //array2=[{"sex":"男","name":"乔佳飞","age":30},{"sex":"女","name":"李帅飞","age":25}]

        String json2 = tfj.getJsonArrayValue(array2, 0);

        System.out.println("json2="+json2);

        //json2={"sex":"男","name":"乔佳飞","age":30}

        /*以下输出

        name=乔佳飞

        sex=男

        age=30

        jsonArr2=男

         * */

        System.out.println("name="+tfj.getJsonValueObj(json2, "name", String.class));

        System.out.println("sex="+tfj.getJsonValueObj(json2, "sex", String.class));

        System.out.println("age="+tfj.getJsonValueObj(json2, "age", Integer.class));

        String jsonArr2 = tfj.getJsonArrayValue(array2, 0, "sex");

        System.out.println("jsonArr2="+jsonArr2);

        /*以下输出

         接口自动化

        东软

        乔佳飞

         */

        System.out.println(tfj.getJsonValue(json));

        System.out.println(tfj.getJsonValue(json,"l_factory"));

        System.out.println(tfj.getJsonValue(json,"l_factory","l_worker"));

    }

    public static void main1(String args[]) {

        TestFastJson tfj = new TestFastJson();

        Project prj = tfj.init();

        String json= tfj.getJsonString(prj);

        prj.setPjName("序列化后修改pjname");

        System.out.println(prj.getPjName());//序列化后修改pjname

        Project po = JSON.parseObject(json,Project.class);

        System.out.println(po.getPjName());//接口自动化

    }

    public void tt(Class clazz) {

        System.out.println(clazz.getSimpleName());

        if(clazz.getName().equals("String")) {

            System.out.println("stringllala");

        }

    }

    public Project init() {

        Project pj = new Project();

        Factory ft1 = new Factory();

        Factory ft2 = new Factory();

        Worker wk1 = new Worker();

        wk1.setName("乔佳飞");

        wk1.setSex("男");

        wk1.setAge(30);

        Worker wk2 = new Worker();

        wk2.setName("李帅飞");

        wk2.setSex("女");

        wk2.setAge(25);

        Worker wk3 = new Worker();

        wk3.setName("魏晓博");

        wk3.setSex("男");

        wk3.setAge(27);

        Worker wk4 = new Worker();

        wk3.setName("王新峰");

        wk3.setSex("男");

        wk3.setAge(26);

        List<Worker> workers1 = new ArrayList<Worker>();

        workers1.add(wk1);

        workers1.add(wk2);

        List<Worker> workers2 = new ArrayList<Worker>();

        workers2.add(wk3);

        workers2.add(wk4);

        ft1.setFcName("东软");

        ft1.setL_worker(workers1);

        ft2.setFcName("亚信");

        ft2.setL_worker(workers2);

        List<Factory> factorys = new ArrayList<Factory>();

        factorys.add(ft1);

        factorys.add(ft2);

        pj.setPjName("接口自动化");

        pj.setWaibao(true);

        pj.setL_factory(factorys);

        return pj;

    }

    /**

     *

     * 将对象转换成json

     * */

    public String getJsonString(Object obj) {

        String json= JSON.toJSONString(obj);

        return json;

    }

    /**

     * 根据key得到json的value

     * */

    public String getJsonValue(String json) {

        JSONObject jo = JSON.parseObject(json);

        String value = jo.getString("pjName");

        return value;

    }

    /**

     * 根据key得到json的集合

     * */

    public JSONArray getJsonArray(String json, String key) {

        JSONObject jo = JSON.parseObject(json);

        JSONArray array = jo.getJSONArray(key);

        return array;

    }

    /**

     * 根据下标得到json数组的值

     * */

    public String getJsonArrayValue(JSONArray array, int index) {

        JSONObject jo_fc = array.getJSONObject(index);

        String json = jo_fc.toJSONString();

        return json;

    }

    /**

     * 根据下标得到json数组的值，再根据key得到该值的value，该值类型是String

     * */

    public String getJsonArrayValue(JSONArray array, int index, String key) {

        JSONObject jo_fc = array.getJSONObject(index);

        String value = jo_fc.getString(key);

        return value;

    }

    /**

     * 根据下标得到json数组的值，再根据key得到该值的value,该值类型是JSONArray

     * */

    public JSONArray getJsonArrayValueIsArray(JSONArray array, int index, String key) {

        JSONObject jo_fc = array.getJSONObject(index);

        JSONArray arrayNew = jo_fc.getJSONArray(key);

        return arrayNew;

    }

    /**

     * 根据对象的类型，自动识别获取该对象的值

     * */

    public Object getJsonValueObj(String json, String key, Class clazz) {

        JSONObject jo = JSON.parseObject(json);

        if(clazz.getSimpleName().equals("String")) {

            String value = jo.getString(key);

            return value;

        }else if(clazz.getSimpleName().equals("Integer")) {

            Integer value = jo.getInteger(key);

            return value;

        }else if (clazz.getSimpleName().equals("Boolean")) {

            Boolean value = jo.getBoolean(key);

            return value;

        }else if(clazz.getSimpleName().equals("JSONArray")) {

            JSONArray array = jo.getJSONArray(key);

            return array;

        }

        else {

            return "error, 暂不支持的类型:"+clazz.toString();

        }        

    }

    public String getJsonValue(String json, String key) {

        JSONObject jo = JSON.parseObject(json);

        JSONArray array = jo.getJSONArray(key);

        JSONObject jo_fc = array.getJSONObject(0);

        String value = jo_fc.getString("fcName");

        return value;

    }

    public String getJsonValue(String json, String key, String keyW) {

        JSONObject jo = JSON.parseObject(json);

        JSONArray array = jo.getJSONArray(key);

        JSONObject jo_fc = array.getJSONObject(0);

        JSONArray arrayW = jo_fc.getJSONArray(keyW);

        JSONObject jo_wk = arrayW.getJSONObject(0);

        String value = jo_wk.getString("name");

        int age = jo_wk.getIntValue("age");

        //System.out.println(age);

        return value;

    }

}

参考：com.alibaba的fastjson简介

参考：高性能JSON框架之FastJson的简单使用

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