"json学习6——>Java读写json格式的文件方法详解"： json学习六——>java 读写json格式的文件方法详解
一、要解决这个问题首先要知道json格式是什么？

json格式：
比如学生有学号，姓名，性别等。
用json表示则为：
{"studno":"11111","studname":"wwww","studsex":"男"}(各个字段都是字符型）

这代表一个学生的信息。

如果多个呢？

[{"studno":"122222","studname":"wwww","studsex":"男"},
{"studno":"11111","studname":"xxxx","studsex":"男"},
{"studno":"33333","studname":"ssss","studsex":"男"}]

这就是json格式。

二、那如何操作json格式的文件呢？

这个更简单了，说白了就是直接读写文件，再把读出来的文件内容格式化成json就可以了。

三、具体操作。

1.我有一个实体类，如下：

public class electset {
public string xueqi;
public string xuenian;
public string starttime;
public string endtime;
public int menshu;
public string isreaddb;
//{"xueqi":,"xuenian":,"starttime":,"endtime":,"renshu":,"isreaddb":}
public string getxueqi() {
    return xueqi;
}
public void setxueqi(string xueqi) {
    this.xueqi = xueqi;
}
public string getxuenian() {
    return xuenian;
}
public void setxuenian(string xuenian) {
    this.xuenian = xuenian;
}
public string getstarttime() {
    return starttime;
}
public void setstarttime(string starttime) {
    this.starttime = starttime;
}
public string getendtime() {
    return endtime;
}
public void setendtime(string endtime) {
    this.endtime = endtime;
}
public int getmenshu() {
    return menshu;
}
public void setmenshu(int menshu) {
    this.menshu = menshu;
}
public string getisreaddb() {
    return isreaddb;
}
public void setisreaddb(string isreaddb) {
    this.isreaddb = isreaddb;
}

}

2.有一个json格式的文件，存的就是他的信息，如下

sets.json:
{"xuenian":"2007-2008","xueqi":"1","starttime":"2009-07-19 08:30","endtime":"2009-07-22 18:00","menshu":"10","isreaddb":"y"}

3.具体操作.
/*
* 取出文件内容，填充对象
*/
public electset findelectset(string path){
    electset electset=new electset();
    string sets=readfile(path);//获得json文件的内容
    jsonobject jo=jsonobject.fromobject(sets);//格式化成json对象
    //system.out.println("------------" jo);
    //string name = jo.getstring("xuenian");
    //system.out.println(name);
    electset.setxueqi(jo.getstring("xueqi"));
    electset.setxuenian(jo.getstring("xuenian"));
    electset.setstarttime(jo.getstring("starttime"));
    electset.setendtime(jo.getstring("endtime"));
    electset.setmenshu(jo.getint("menshu"));
    electset.setisreaddb(jo.getstring("isreaddb"));
    return electset;
}
//设置属性，并保存
public boolean setelect(string path,string sets){
    try {
     writefile(path,sets);
     return true;
    } catch (ioexception e) {
     // todo auto-generated catch block
     e.printstacktrace();
     return false;
    }
}
//读文件，返回字符串
public string readfile(string path){
     file file = new file(path);
     bufferedreader reader = null;
     string laststr = "";
     try {
      //system.out.println("以行为单位读取文件内容，一次读一整行：");
      reader = new bufferedreader(new filereader(file));
      string tempstring = null;
      int line = 1;
      //一次读入一行，直到读入null为文件结束
      while ((tempstring = reader.readline()) != null) {
       //显示行号
       system.out.println("line " line ": " tempstring);
       laststr = laststr tempstring;
       line ;
      }
      reader.close();
     } catch (ioexception e) {
      e.printstacktrace();
     } finally {
      if (reader != null) {
       try {
        reader.close();
       } catch (ioexception e1) {
       }
      }
     }
     return laststr;
}
          //把json格式的字符串写到文件
public void writefile(string filepath, string sets) throws ioexception {
     filewriter fw = new filewriter(filepath);
     printwriter out = new printwriter(fw);
     out.write(sets);
     out.println();
     fw.close();
     out.close();
    }

4.调用，使用（在网站的controller里调用的）

//取出json对象
public void getelectsettings(httpservletrequest request,
     httpservletresponse response) throws exception {
    electset electset=new electset();
    string abspath = request.getrealpath("\\");
    string filepath = abspath "public\\sets\\electsets.json";
    electset=businessservice.findelectsets(filepath);//这里是调用，大家自己改改，我调用的业务层 的。
    jsonarray jsonitems = new jsonarray();
    jsonitems.add(electset);
    jsonobject jo=new jsonobject();
    jo.put("data", jsonitems);
    system.out.println(jo);
    request.setcharacterencoding("utf-8");
    response.setcontenttype("application/json;charset=utf-8");
    printwriter out = response.getwriter();
    out.print(jo);
}

//修改json文件
public void changeelectset(httpservletrequest request,
     httpservletresponse response) throws exception {
    request.setcharacterencoding("utf-8");
    response.setcontenttype("text/json;charset=utf-8");
    log.info("reach changeelectset");
    string json = (string) request.getparameter("json").trim();
    log.info("change electset");
    log.info(json);
    electset sets = new electset();
    jsonobject jsonobject = jsonobject.fromobject(json);
    sets = (electset) jsonobject.tobean(jsonobject, electset.class);
    if(sets.getisreaddb()=="false"){
     sets.setisreaddb("否");
    }
    else{
     sets.setisreaddb("是");
    }
    string changes="{\"xuenian\":\"";//因为json的属性要用引号，所以要用\"转义一下
    changes =sets.getxuenian() "\",\"xueqi\":\"" sets.getxueqi() "\",\"starttime\":\"" sets.getstarttime() "\",\"endtime\":\"" sets.getendtime() "\",\"menshu\":\"" sets.getmenshu() "\",\"isreaddb\":\"" sets.getisreaddb() "\"}";
    system.out.println(changes);
    string abspath = request.getrealpath("\\");
    string filepath = abspath "public\\sets\\electsets.json";
    if(businessservice.changeelectsets(filepath, changes)){
     log.info("选课设置修改成功");
     request.setcharacterencoding("utf-8");
     response.setcontenttype("text/json;charset=utf-8");
     response.getwriter().write("{success: true}");
    } else {
     response.getwriter().write("{errors:'选课设置修改失败，请重新尝试!'}");
    }
}

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