最近刚好做一个app，然后就不太会json数据交互，就上网查了一些，发现并没有快餐类的代码。所以这里就直接给大家安卓端和服务器端的快餐代码，对初学者还是很有帮助的，大家可以依葫芦画瓢，不喜勿喷

首先是安卓端，我主要上传一个User对象，下面是安卓端的代码通过okhttp3，gson编译成json格式上传

需要引用

compile 'com.google.code.gson:gson:2.8.1'

下面是客户端的一个功能的代码，主要将对象User上传给服务器，其中通过bundle将返回的对象传入到别的activity。本来想删除的，但是对于初学者应该还是很实用，gson.toJson（）这个方法就是将user对象编译成json格式的字符串，方便上传给服务器

    /**
     * 发送post请求
     */
    public User user = new User();
    public void postRequest(){
        OkHttpClient client = new OkHttpClient();

        user.setUsername(username.getText().toString());
        user.setPassword(content.getText().toString());
        Gson gson = new Gson();
        //使用Gson将对象转换为json字符串
        String json = gson.toJson(user);
        RequestBody requestBody = FormBody.create(MediaType.parse("application/json; charset=utf-8")
                , json);
        Request request = new Request.Builder()
                .url(httpURL+"/HttpWeb/LoginServlet")//请求的url
                .post(requestBody)
                .build();

        Call call = client.newCall(request);
        call.enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {

            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                final  String res = response.body().string();
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        resultTV.setText(res);
                        Log.v("Main.ID=",res);
                        if (!res.equals(null)){
                            Toast.makeText(Main.this,"登陆成功",Toast.LENGTH_SHORT).show();
                            user.setId(res);
                            Intent intent = new Intent();
                            intent.setClass(Main.this,MainActivity.class);//跳转到加载界面
                            Bundle bundle = new Bundle();
                            bundle.putParcelable("user", user);
                            intent.putExtras(bundle);
                            startActivity(intent);
                        }else{
                            Toast.makeText(Main.this,"登陆失败",Toast.LENGTH_SHORT).show();
                        }
                    }
                });
            }
        });
    }

User表，其中实现接口Parcelable是为了让bundle可以传递这个对象，使用bundle.putParcelable()这个办法

import android.os.Parcel;
import android.os.Parcelable;

import java.io.Serializable;

/**
 * Created by acer1 on 2018/4/5.
 */

public class User implements Parcelable,Serializable{
    private String id;
    private String username;
    private String password;
    private String Nickname;
    private String Individuality_signature;

    public User(Parcel in) {
        id = in.readString();
        username = in.readString();
        password = in.readString();
    }

    public static final Creator<User> CREATOR = new Creator<User>() {
        @Override
        public User createFromParcel(Parcel in) {
            return new User(in);
        }

        @Override
        public User[] newArray(int size) {
            return new User[size];
        }
    };

    public User() {

    }

    public String getNickname() {
        return Nickname;
    }

    public void setNickname(String nickname) {
        Nickname = nickname;
    }

    public String getIndividuality_signature() {
        return Individuality_signature;
    }

    public void setIndividuality_signature(String individuality_signature) {
        Individuality_signature = individuality_signature;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }


    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(id);
        dest.writeString(username);
        dest.writeString(password);
    }
}

现在客户端基本就完事了，下面是服务器的代码，我开始学的时候就主要想学怎么接收json格式的数据，我相信大家也是想学怎么接收json数据格式的数据，通过gson将接收的数据解析成对象，看代码。我们还要在服务器里面写一个javabean，让json数据映射成这个javabean,方便提取数据

首先我们导入一些包，让我们可以接收到json数据

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	
	response.setContentType("application/json");
        response.setCharacterEncoding("UTF-8");
        request.setCharacterEncoding("UTF-8");

        /**
         * 接收json
         */
        BufferedReader reader = request.getReader();
        String json = reader.readLine();
        System.out.println(json);
        Gson gson =new Gson();
        User user = gson.fromJson(json, User.class);
        System.out.println(user.getUsername());
        System.out.println(user.getPassword());
        PrintWriter out = response.getWriter();
        Integer msg;
		try {
			msg = UserDao.selectUser(user);
			out.print(msg);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
        reader.close();
	}

其中提取json数据和解析的代码就是下面这段代码

        response.setContentType("application/json");
        response.setCharacterEncoding("UTF-8");
        request.setCharacterEncoding("UTF-8");

        /**
         * 接收json
         */
        BufferedReader reader = request.getReader();
        String json = reader.readLine();
        System.out.println(json);
        Gson gson =new Gson();
        User user = gson.fromJson(json, User.class);
        System.out.println(user.getUsername());
        System.out.println(user.getPassword());

然后就是服务器端的javabean

public class User {
	
	private String id;
	private String username;
	private String password;
	private String Nickname;
	private String Individuality_signature;
	
	
	
	public String getNickname() {
		return Nickname;
	}
	public void setNickname(String nickname) {
		Nickname = nickname;
	}
	public String getIndividuality_signature() {
		return Individuality_signature;
	}
	public void setIndividuality_signature(String individuality_signature) {
		Individuality_signature = individuality_signature;
	}
	public String getId() {
		return id;
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	

}

到这里基本的过程就结束了，从安卓端上传json数据到服务器端解析json数据，将json数据解析成javabean对象。不知道对初学者有没有帮助，又不懂的可以直接@我，哈哈哈哈