Java中json文件与json对象之间的转换

• 一、json文件解析json对象
• • per.json文件内容
  • 方式一：相对路径读取
  • 方式二：绝对路径读取
  • 运行结果
• 二、json对象解析json文件
• • 运行结果

一、json文件解析json对象

per.json文件内容

{
  "name" : "zhangsan",
  "age" : 23,
  "address" :
  {
    "homeAddress" : "杭州",
    "schoolAddress" : "上海"
  }
}

方式一：相对路径读取

@Test
public void demo1() throws IOException {
    //文件-->String(方式一)
    InputStream in = super.getClass().getClassLoader().getResourceAsStream("com/dmj/json/lab2/per.json");//相对路径
    byte[] bs = new byte[10];//定义缓冲区，大小为1
    int len = -1;
    StringBuffer sb = new StringBuffer();//字符串拼接为sb（读取一个拼接一个）
    while ((len = in.read(bs)) != -1){//不断向缓冲区读取内容，如果不等于-1，说明有内容
    	String str = new String(bs,0,len);//读取的字节数组转换字符串
    	sb.append(str);//进行拼接
    }
    //StringBuffer-->String
    String s = sb.toString();
    //String-->JSON
    JSONObject json = new JSONObject(s);
    System.out.println(json);
}

方式二：绝对路径读取

@Test
public void demo2() throws IOException {
    //文件-->String(方式二，需要commons-io.jar包)
    String s = FileUtils.readFileToString(
            new File("D:\\javaSpace\\java_questions\\src\\com\\dmj\\json\\lab2\\per.json"),
                     "utf8");//绝对路径
    //String-->JSON
    JSONObject json = new JSONObject(s);
    System.out.println(json);
}

运行结果

二、json对象解析json文件

• 创建Person对象，此处省略了有参/无参构造方法、get()方法、set()方法；

public class Person {
    private String name;
    private int age;
    private Address address;
}

public class Address {
    private String homeAddress;
    private String schoolAddress;
}

• map–>json

@Test
public void demo3() throws IOException {
    //准备json数据(map-->json)
    Map<String, Person> map = new HashMap<>();
    Person p1 = new Person("zs",20,new Address("杭州","宁波"));
    Person p2 = new Person("ls",21,new Address("台州","上海"));
    Person p3 = new Person("ww",22,new Address("衢州","南京"));
    map.put("zs",p1);
    map.put("ls",p2);
    map.put("ww",p3);
    //map-->json
    JSONObject json = new JSONObject(map);
    //生成json文件
    Writer w = new FileWriter("D:\\javaSpace\\java_questions\\src\\com\\dmj\\json\\lab2\\per1.json");
    json.write(w);
    w.close();
    System.out.println("生成json文件成功！");
}

运行结果

• 生成per1.json文件内容

{
  "ww":{"address":{"schoolAddress":"南京","homeAddress":"衢州"},"name":"ww","age":22},
  "zs":{"address":{"schoolAddress":"宁波","homeAddress":"杭州"},"name":"zs","age":20},
  "ls":{"address":{"schoolAddress":"上海","homeAddress":"台州"},"name":"ls","age":21}
}