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关于fastjson的常见API详解

作者：尽力漂亮

这篇文章主要介绍了关于fastjson的常见API详解,Fastjson是一个Java库，可用于将Java对象转换为其JSON表示,它还可用于将JSON字符串转换为等效的Java对象,Fastjson可以处理任意Java对象，包括您没有源代码的预先存在的对象,需要的朋友可以参考下

简介

首先，介绍一下fastjson。fastjson是由alibaba开源的一套json处理器。与其他json处理器（如Gson，Jackson等）和其他的Java对象序列化反序列化方式相比，有比较明显的性能优势。

maven 添加配置：

< !-- 阿里fastjson包JSON转换–>
< dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.47</version>
< /dependency>

常见API

1. 将对象序列化成json字符串

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

效果

{
	"l_factory": [{
		"fcName": "淘宝",
		"l_worker": [{
			"age": 26,
			"name": "李飞",
			"sex": "男"
		}, {
			"age": 0
		}, {
			"age": 0
		}, {
			"age": 0
		}]
	}, {
		"fcName": "拼多多",
		"l_worker": []
	}],
	"pjName": "接口自动化",
	"waibao": true
}

2. 将json字符串反序列化成对象 Project

com.alibaba.fastjson.JSON.parseObject(String text, Class clazz)

 System.out.println("parseObject 将json字符串反序列化成对象------" + "waibao="+ testFastJson.getJsonValueObj(json, "waibao", Boolean.class));

效果

 waibao=true

3. 将json字符串反序列化成JSON对象 JSONObject

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

[{
	"l_worker": [{
		"sex": "男",
		"name": "张三",
		"age": 39
	}, {
		"sex": "男",
		"name": "李四",
		"age": 24
	}],
	"fcName": "淘宝"
}, {
	"l_worker": [{
		"sex": "女",
		"name": "王香",
		"age": 26
	}, {
		"sex": "男",
		"name": "李飞",
		"age": 26
	}],
	"fcName": "拼多多"
}]

4. 根据key 得到json中的json数组 JSONArray

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

[{
	"sex": "男",
	"name": "张三",
	"age": 39
}, {
	"sex": "男",
	"name": "李四",
	"age": 24
}]
[{
	"sex": "男",
	"name": "张三",
	"age": 39
}, {
	"sex": "男",
	"name": "李四",
	"age": 24
}]

5. 根据下标拿到json数组的json对象 JSONObject

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

效果

{
	"sex": "男",
	"name": "张三",
	"age": 39
}

6.根据key拿到json的字符串值 String

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

api详细案例

Project

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

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

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;
    }
}

TestFastJson

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 testFastJson = new TestFastJson();
		Project project = testFastJson.init();
		String json = testFastJson.getJsonString(project);
		// System.out.println("json="+json);
		// {"l_factory":[{"fcName":"淘宝","l_worker":[{"age":26,"name":"李飞","sex":"男"},{"age":0},{"age":0},{"age":0}]},{"fcName":"拼多多","l_worker":[]}],"pjName":"接口自动化","waibao":true}
		// System.out.println("parseObject 将json字符串反序列化成对象------" + "waibao="
		// + testFastJson.getJsonValueObj(json, "waibao", Boolean.class));
		// waibao=true
		JSONArray array = (JSONArray) testFastJson.getJsonValueObj(json, "l_factory", JSONArray.class);
		// System.out.println("array=" + array.toString());
		// array=[{"l_worker":[{"sex":"男","name":"张三","age":39},{"sex":"男","name":"李四","age":24}],"fcName":"淘宝"},{"l_worker":[{"sex":"女","name":"王香","age":26},{"sex":"男","name":"李飞","age":26}],"fcName":"拼多多"}]
		// String jsonArr = testFastJson.getJsonArrayValue(array, 0, "fcName");
		// System.out.println("fcname:" + jsonArr);
		// fcname:淘宝
		JSONArray array2 = testFastJson.getJsonArrayValueIsArray(array, 0, "l_worker");
		// System.out.println("array2=" + array2.toString());
		// array2=[{"sex":"男","name":"张三","age":39},{"sex":"男","name":"李四","age":24}]
		String json2 = testFastJson.getJsonArrayValue(array2, 0);
		// System.out.println("json2="+json2);
		// {"sex":"男","name":"张三","age":39}
		// System.out.println("name"+testFastJson.getJsonValueObj(json, key, clazz));
		/*
		 * 以下输出 name=张三 sex=男 age=39 jsonArr2=男
		 * 
		 */
		System.out.println("name=" + testFastJson.getJsonValueObj(json2, "name", String.class));
		System.out.println("sex=" + testFastJson.getJsonValueObj(json2, "sex", String.class));
		System.out.println("age=" + testFastJson.getJsonValueObj(json2, "age", Integer.class));
		String jsonArr2 = testFastJson.getJsonArrayValue(array2, 0, "sex");
		System.out.println("jsonArr2=" + jsonArr2);
		/*
		 * 接口自动化 淘宝 张三
		 * 
		 */
		System.out.println(testFastJson.getJsonValue(json));
		System.out.println(testFastJson.getJsonValue(json, "l_factory"));
		System.out.println(testFastJson.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");
		}
	}
	/**
	 * 将对象转化为json
	 * 
	 * @param project
	 * @return
	 */
	private String getJsonString(Object object) {
		// TODO Auto-generated method stub
		String json = JSON.toJSONString(object);
		return json;
	}
	/**
	 * 初始化
	 * 
	 * @return
	 */
	private Project init() {
		Project project = new Project();
		Factory f1 = new Factory();
		Factory f2 = new Factory();
		Worker wk1 = new Worker();
		wk1.setName("张三");
		wk1.setAge(39);
		wk1.setSex("男");
		Worker wk2 = new Worker();
		wk2.setName("李四");
		wk2.setAge(24);
		wk2.setSex("男");
		Worker wk3 = new Worker();
		wk3.setName("王香");
		wk3.setAge(26);
		wk3.setSex("女");
		Worker wk4 = new Worker();
		wk4.setName("李飞");
		wk4.setAge(26);
		wk4.setSex("男");
		List<Worker> workers1 = new ArrayList<>();
		workers1.add(wk1);
		workers1.add(wk2);
		List<Worker> workers2 = new ArrayList<>();
		workers2.add(wk3);
		workers2.add(wk4);
		f1.setFcName("淘宝");
		f1.setL_worker(workers1);
		f2.setFcName("拼多多");
		f2.setL_worker(workers2);
		List<Factory> factorys = new ArrayList<Factory>();
		factorys.add(f1);
		factorys.add(f2);
		project.setPjName("接口自动化");
		project.setWaibao(true);
		project.setL_factory(factorys);
		return project;
	}
	/**
	 * 根据key得到json的value
	 * 
	 */
	public String getJsonValue(String json) {
		JSONObject jsonObject = JSON.parseObject(json);
		String value = jsonObject.getString("pjName");
		return value;
	}
	/**
	 * 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();
		}
	}
	/**
	 * 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;
	}
	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");
		return value;
	}
	/**
	 * 根据下标得到json数组的值
	 * 
	 * @return
	 */
	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j'son数组的值，再根据key得到该值的value,该值类型是String
	 * 
	 * @param array
	 * @param index
	 * @param key
	 * @return
	 */
	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string
	 * 
	 * @param array
	 * @return
	 */
	public JSONArray getJsonArrayValueIsArray(JSONArray array, int index, String key) {
		JSONObject jo_fc = array.getJSONObject(index);
		JSONArray arrayNew = jo_fc.getJSONArray(key);
		return arrayNew;
	}
}

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