java— 读取JSON文件的多种方式

大部分内容参考自： https://blog.csdn.net/csdn_halon/article/details/120287992

在开发过程中有时会遇到需要读取本地.json文件的需求，通常会自己写Reader代码去读，但是这么做写出来的代码有些繁琐（需要关流、创建StringBuilder对象等操作）。最近发现几个小工具可以让需求代码变得更加简洁。

准备：

json文件：D:\test.json

{
    "ID": 10001,
    "detail": "detail",
    "json_format_version": 1.0,
    "other_info": {
        "array_one": [
            [855, 410],
            [854, 411],
            [847, 411],
            [846, 410],
            [845, 410],
            [844, 409]
        ],
        "array_two": [
            [832, 303],
            [829, 303],
            [828, 302],
            [825, 302],
            [824, 301]
        ],
        "array_three": [
            [1013, 224],
            [1012, 225],
            [1010, 225],
            [1009, 226],
            [1023, 224]
        ],
        "point": [853, 310],
        "boolean": true
    }
}

1.使用FileReader读取json文件

1.1、添加依赖

    <dependencies>
        <dependency>
           <groupId>com.alibaba</groupId>
           <artifactId>fastjson</artifactId>
           <version>2.0.12</version>
        </dependency>
    </dependencies>

1.2源代码

import com.alibaba.fastjson.JSON;
 
import java.io.*;
 
public class ReadLocalJsonFileDemo {
    publicstatic void main(String[] args) throws IOException {
        Filefile = new File("D:\\test.json");
       readerMethod(file);
 
    }
 
    privatestatic void readerMethod(File file) throws IOException {
       FileReader fileReader = new FileReader(file);
        Readerreader = new InputStreamReader(new FileInputStream(file), "Utf-8");
        int ch= 0;
       StringBuffer sb = new StringBuffer();
        while((ch = reader.read()) != -1) {
           sb.append((char) ch);
        }
       fileReader.close();
       reader.close();
        StringjsonStr = sb.toString();
       System.out.println(JSON.parseObject(jsonStr));
    }
}

1.3.控制台输出

{"other_info":{"array_two":[[832,303],[829,303],[828,302],[825,302],[824,301]],"array_three":[[1013,224],[1012,225],[1010,225],[1009,226],[1023,224]],"boolean":true,"array_one":[[855,410],[854,411],[847,411],[846,410],[845,410],[844,409]],"point":[853,310]},"ID":10001,"detail":"detail","json_format_version":1.0}

2.使用jacksonAPI读取json文件

2.1、添加依赖

    <dependencies>
        <dependency>
           <groupId>com.fasterxml.jackson.core</groupId>
           <artifactId>jackson-databind</artifactId>
           <version>2.13.3</version>
        </dependency>
    </dependencies>

2.2源代码

import com.fasterxml.jackson.databind.ObjectMapper;
 
import java.io.File;
import java.io.IOException;
import java.util.Map;
 
public class ReadLocalJsonFileDemo {
    publicstatic void main(String[] args) throws IOException {
        Filefile = new File("D:\\test.json");
       jacksonMethod(file);
    }
 
    privatestatic void jacksonMethod(File file) throws IOException {
       ObjectMapper objectMapper = new ObjectMapper();
       System.out.println(objectMapper.readValue(file, Map.class));
    }
}

2.3.控制台输出

{ID=10001,detail=detail, json_format_version=1.0, other_info={array_one=[[855, 410],[854, 411], [847, 411], [846, 410], [845, 410], [844, 409]], array_two=[[832,303], [829, 303], [828, 302], [825, 302], [824, 301]], array_three=[[1013,224], [1012, 225], [1010, 225], [1009, 226], [1023, 224]], point=[853, 310],boolean=true}}

3.使用nio读取json文件

3.1、添加依赖

    <dependencies>
        <dependency>
           <groupId>com.alibaba</groupId>
           <artifactId>fastjson</artifactId>
           <version>2.0.12</version>
        </dependency>
    </dependencies>

3.2源代码

import com.alibaba.fastjson.JSONObject;
 
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
 
public class ReadLocalJsonFileDemo {
    publicstatic void main(String[] args) throws IOException {
        Filefile = new File("D:\\test.json");
       nioMethod(file);
    }
 
    privatestatic void nioMethod(File file) throws IOException {
        StringjsonString = new String(Files.readAllBytes(Paths.get(file.getPath())));
       System.out.println(JSONObject.parseObject(jsonString));
    }
}