一篇文章搞定fastjson的主要用法

alibaba fastjson
JavaSE
发布日期:   2022-06-08
更新日期:   2022-06-08
文章字数:   1.4k
阅读时长:   7 分
阅读次数:  

一、FastJson简介

fastjson是用于java后台处理json格式数据的一个工具包，包括“序列化”和“反序列化”两部分，它具备如下特征：

  • 速度最快，测试表明，fastjson具有极快的性能，超越任其他的java json parser。
  • 功能强大，完全支持java bean、集合、Map、日期、Enum，支持范型，支持自省。
  • 无依赖，能够直接运行在Java SE 5.0以上版本

fastjson的作用就是把 java 对象转化为字符串，把字符串转化为java对象，然后方便进行后续的逻辑处理。

二、FastJson主要类

fastjson对于json格式字符串的解析主要用到了一下三个类

JSON

用于JSON格式字符串与JSON对象及javaBean之间的转换

package com.alibaba.fastjson;
/**
 * This is the main class for using Fastjson. You usually call these two methods {@link #toJSONString(Object)} and {@link #parseObject(String, Class)}.
 * 
 * <p>Here is an example of how fastjson is used for a simple Class:
 *
 * <pre>
 * Model model = new Model();
 * String json = JSON.toJSONString(model); // serializes model to Json
 * Model model2 = JSON.parseObject(json, Model.class); // deserializes json into model2
 * </pre>
 * 
* <p>If the object that your are serializing/deserializing is a {@code ParameterizedType}
 * (i.e. contains at least one type parameter and may be an array) then you must use the
 * {@link #toJSONString(Object)} or {@link #parseObject(String, Type, Feature[])} method.  Here is an
 * example for serializing and deserialing a {@code ParameterizedType}:
 * 
 * <pre>
 * String json = "[{},...]";
 * Type listType = new TypeReference&lt;List&lt;Model&gt;&gt;() {}.getType();
 * List&lt;Model&gt; modelList = JSON.parseObject(json, listType);
 * </pre>
 * 
 * @see com.alibaba.fastjson.TypeReference
 * 
 * @author wenshao[szujobs@hotmail.com]
 */
public abstract class JSON implements JSONStreamAware, JSONAware{
    //需要重点关注的方法
    parse
    parseObject
    parseArray
    toJSONString
    toJSONBytes
    writeJSONString
    toJavaObject
}

JSONObject

JSONObject	//需要重点关注的方法
	parseObject
    getJSONArray
    getJSONObject
    getObject
    containsKey

JSONArray

三、准备工作

实体类：Resp

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Resp implements Serializable {
    private static final long serialversionuid = -6957361951748382519L;

    private String id;
    private String suborderNo;
    private String organUnitType;
    private String action;
    private String parent;
    private String organUnitFullName;
    private Long ordinal;
}

实体类：MyERROR

@Data
@AllArgsConstructor
@NoArgsConstructor
public class MyERROR implements Serializable {
    private String code;
    private String message;
    private String success;

    private List<Resp> data = new ArrayList<>();
}

json字符串：

{
    "meta": {
        "code": "0",
        "message": "同步成功!"
    },
    "data": {
        "orderno": "U_2018062790915774",
        "suborderno": "SUB_2018062797348039",
        "type": "organunit",
        "result": {
            "organunit": {
                "totalCount": 2,
                "successCount": 0,
                "failCount": 2,
                "errors": [
                    {
                        "code": "UUM70004",
                        "message": "组织单元名称不能为空",
                        "data": {
                            "id": "254",
                            "suborderNo": "SUB_2018062797348039",
                            "organUnitType": "部门",
                            "action": "add",
                            "parent": "10000",
                            "ordinal": 0,
                            "organUnitFullName": "组织单元全称"
                        },
                        "success": false
                    },
                    {
                        "code": "UUM70004",
                        "message": "组织单元名称不能为空",
                        "data": {
                            "id": "255",
                            "suborderNo": "SUB_2018062797348039",
                            "organUnitType": "部门",
                            "action": "add",
                            "parent": "10000",
                            "ordinal": 0,
                            "organUnitFullName": "组织单元全称"
                        },
                        "success": false
                    }
                ]
            },
            "role": {
                "totalCount": 0,
                "successCount": 0,
                "failCount": 0,
                "errors": []
            },
            "user": {
                "totalCount": 0,
                "successCount": 0,
                "failCount": 0,
                "errors": []
            }
        }
    }
}

看一下格式化之后的json数据：

四、示例

4.1 java对象转JSON字符串

//java对象转json字符串
public static void beanTojson() {
    Resp resp = new Resp();
    resp.setAction("add");
    resp.setId("1");
    resp.setOrdinal(8L);
    resp.setOrganUnitFullName("testJSON");
    resp.setParent("0");
    resp.setSuborderNo("58961");

    String s = JSON.toJSONString(resp);
    System.out.println("toJsonString()方法：s=" + s);
    //输出结果{"action":"add","id":"1","ordinal":8,"organUnitFullName":"testJSON","parent":"0","suborderNo":"58961"}
}

4.2 JSON字符串转JSON对象

//json字符串转json对象
public static void jsonToJsonBean() {
    String s ="{\"action\":\"add\",\"id\":\"1\",\"ordinal\":8,\"organUnitFullName\":\"testJSON\",\"parent\":\"0\",\"suborderNo\":\"58961\"}";

    JSONObject jsonObject = JSON.parseObject(s);
    String action = jsonObject.getString("action");
    String id = jsonObject.getString("id");
    System.out.println("action ="+action);//add
    System.out.println("id ="+id);//1
    System.out.println("jsonObject ="+jsonObject);
    //jsonObject ={"parent":"0","organUnitFullName":"testJSON","action":"add","id":"1","suborderNo":"58961","ordinal":8}
}

4.3 复杂JSON格式字符串与JSONObject之间的转换

public static void jsonToBean() {
    String str ="{\"meta\":{\"code\":\"0\",\"message\":\"同步成功!\"},\"data\":{\"orderno\":\"U_2018062790915774\",\"suborderno\":\"SUB_2018062797348039\",\"type\":\"organunit\",\"result\":{\"organunit\":{\"totalCount\":2,\"successCount\":0,\"failCount\":2,\"errors\":[{\"code\":\"UUM70004\",\"message\":\"组织单元名称不能为空\",\"data\":{\"id\":\"254\",\"suborderNo\":\"SUB_2018062797348039\",\"organUnitType\":\"部门\",\"action\":\"add\",\"parent\":\"10000\",\"ordinal\":0,\"organUnitFullName\":\"组织单元全称\"},\"success\":false},{\"code\":\"UUM70004\",\"message\":\"组织单元名称不能为空\",\"data\":{\"id\":\"255\",\"suborderNo\":\"SUB_2018062797348039\",\"organUnitType\":\"部门\",\"action\":\"add\",\"parent\":\"10000\",\"ordinal\":0,\"organUnitFullName\":\"组织单元全称\"},\"success\":false}]},\"role\":{\"totalCount\":0,\"successCount\":0,\"failCount\":0,\"errors\":[]},\"user\":{\"totalCount\":0,\"successCount\":0,\"failCount\":0,\"errors\":[]}}}}";
    
    JSONObject jsonObject = JSON.parseObject(str);
    JSONObject data = jsonObject.getJSONObject("data");
    JSONObject result = data.getJSONObject("result");

    String organunit1 = result.getString("organunit");
    System.out.println(organunit1);
    JSONObject organunit = result.getJSONObject("organunit");

    JSONArray errors2 = organunit.getJSONArray("errors");

    List<MyERROR> errors = JSON.parseObject(errors2.toJSONString(), new TypeReference<List<MyERROR>>() {});
    for (MyERROR error : errors) {
        System.out.println(error);
    }

    System.out.println("==========================>");
    //JSONObject 可以链式调用
    JSONArray jsonArray = JSON.parseObject(str).getJSONObject("data").getJSONObject("result").getJSONObject("organunit").getJSONArray("errors");
    List<MyERROR> myERRORS = JSON.parseObject(jsonArray.toJSONString(), new TypeReference<List<MyERROR>>() {});
    for (MyERROR error : myERRORS) {
        System.out.println(error);
    }
}

打印结果：

image-20220608115351374

4.4 JSON字符串转Java简单对象

public static void jsonStrToJavaBean() {
    String s ="{\"action\":\"add\",\"id\":\"1\",\"ordinal\":8,\"organUnitFullName\":\"testJSON\",\"parent\":\"0\",\"suborderNo\":\"58961\"}";
    Resp data = JSON.parseObject(s, Resp.class);
    System.out.println("data对象"+data.toString());
    System.out.println("action="+data.getAction()+"---id="+data.getId());       //1

    //另一种方式转对象
    Resp dd = JSON.parseObject(s, new TypeReference<Resp>() {});
    System.out.println("另一种方式获取data对象"+dd.toString());
    System.out.println("另一种方式获取="+dd.getAction()+"---id="+dd.getId());      //1
}

4.5 JSON字符串 数组类型与Java对象的转换

public static void jsonStrToJSONArray() {
    String str = "{\"errors\":[{\"code\":\"UUM70004\",\"message\":\"组织单元名称不能为空\",\"data\":{\"id\":\"254\",\"suborderNo\":\"SUB_2018062797348039\",\"organUnitType\":\"部门\",\"action\":\"add\",\"parent\":\"10000\",\"ordinal\":0,\"organUnitFullName\":\"组织单元全称\"},\"success\":false},{\"code\":\"UUM70004\",\"message\":\"组织单元名称不能为空\",\"data\":{\"id\":\"255\",\"suborderNo\":\"SUB_2018062797348039\",\"organUnitType\":\"部门\",\"action\":\"add\",\"parent\":\"10000\",\"ordinal\":0,\"organUnitFullName\":\"组织单元全称\"},\"success\":false}]}";

    JSONArray error = JSON.parseObject(str).getJSONArray("errors");
    List<MyERROR> errors = JSON.parseObject(error.toJSONString(), 
                                            new TypeReference<List<MyERROR>>() {});
    for (MyERROR e: errors) {
        //Error的属性
        System.out.println("MyERROR.message属性="+e.getMessage());
        System.out.println("MyERROR.code属性="+e.getCode());
        System.out.println("MyERROR.success属性="+e.getSuccess());

        List<Resp> datas = e.getData();
        for (Resp d: datas) {
            System.out.println("data对象属性="+d.getId());
            System.out.println("data对象属性="+d.getAction());
            System.out.println("data对象属性="+d.getSuborderNo());
        }
        System.out.println("------------------------------>");
    }
}

4.6 Java对象转JSON对象

public static void beanToJsonObject() {
    Resp data = new Resp();
    data.setAction("add");
    data.setId("1");
    data.setOrdinal(8L);
    data.setOrganUnitFullName("testJSON");
    data.setParent("0");
    data.setSuborderNo("58961");

    JSONObject jsonObject = JSONObject.parseObject(JSON.toJSONString(data));
    JSONObject jsonObj = (JSONObject) JSON.toJSON(data);
    JSON json = (JSON) JSON.toJSON(data);
    System.out.println(jsonObj);
    System.out.println(json);
    System.out.println(jsonObject);
}
文章作者: CoderXiong
文章链接: http://bfd2018.github.io/2022/06/08/javase/yi-pian-wen-zhang-gao-ding-fastjson-de-zhu-yao-yong-fa/
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