一、实现效果：

mysql数据库表里的情况：
安卓可以‘user_table’中的数据，注册新增用户，用户登陆。【写的很简单】

二、提前需要：

springboot+mysql，连接好。
spingboot中分别写get（带参数、不带参数）和post（带参数）三个接口
查询到本机的IP地址

三、代码

1. 安卓部分

1. build.gradle

 implementation 'com.squareup.okhttp3:okhttp:4.4.1'
 implementation 'com.google.code.gson:gson:2.8.5'

在这里插入图片描述

2. login.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".LogiActivity">


    <Button
        android:id="@+id/button"
        android:onClick="getRequest"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="查询所有用户" />

    <Button
        android:id="@+id/button3"
        android:onClick="getRequestParam"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="注册" />

    <Button
        android:id="@+id/button4"
        android:onClick="postRequestParam"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="登陆" />

</LinearLayout>

3. loginActivity。【重要！！这部分包含了get、post】

package com.example.mainapp_bleda2;

import android.os.Bundle;
import android.util.Log;
import android.view.View;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import com.example.mainapp_bleda2.bean.PostRequest;
import com.google.gson.Gson;

import java.io.IOException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.TimeUnit;

import okhttp3.Callback;
import okhttp3.MediaType;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;

public class LogiActivity extends AppCompatActivity {
    private static final String TAG = "Login";

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login2);
    }

    //get请求不带参数
    public void getRequest(View view) {
        //先来okhttp客户端
        OkHttpClient okHttpClient = new OkHttpClient.Builder()
                .connectTimeout(8000, TimeUnit.MICROSECONDS).build();
        // 请求
        Request request = new Request.Builder()
                .get()
                .url("http://172.20.10.2:8080/user/selectAll")
                .build();
        // 返回数据的处理
        okHttpClient.newCall(request).enqueue(new Callback() {
            @Override
            public void onResponse(@NonNull okhttp3.Call call, @NonNull Response response) throws IOException {
                Log.e(TAG, "onResponse: " + response.code());
                Log.e(TAG, "onResponse: " + response.body().string());
            }

            @Override
            public void onFailure(@NonNull okhttp3.Call call, @NonNull IOException e) {
                Log.e(TAG, "onFailure" + e.toString());
            }
        });
    }

    //get请求带参数
    public void getRequestParam(View view) {
        //先来okhttp客户端
        OkHttpClient okHttpClient = new OkHttpClient.Builder()
                .connectTimeout(8000, TimeUnit.MICROSECONDS).build();

        Map<String, String> map = new HashMap<>();
        map.put("user_account", "444");
        map.put("user_pwd", "111");
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("?");
        //迭代器
        Iterator<Map.Entry<String, String>> iterator = map.entrySet().iterator();
        while (iterator.hasNext()){
            Map.Entry<String, String> next = iterator.next();
            stringBuilder.append(next.getKey());
            stringBuilder.append("=");
            stringBuilder.append(next.getValue());
            if (iterator.hasNext()){
                stringBuilder.append("&");
            }
        }
        String str = stringBuilder.toString();
        // 请求
        Request request = new Request.Builder()
                .get()
                .url("http://172.20.10.2:8080/user/register"+str)
                .build();
        // 返回数据的处理
        okHttpClient.newCall(request).enqueue(new Callback() {
            @Override
            public void onResponse(@NonNull okhttp3.Call call, @NonNull Response response) throws IOException {
                Log.e(TAG, "onResponse: " + response.code());
                Log.e(TAG, "onResponse: " + response.body().string());
            }

            @Override
            public void onFailure(@NonNull okhttp3.Call call, @NonNull IOException e) {
                Log.e(TAG, "onFailure" + e.toString());
            }
        });
    }

    //post请求带参数
    public void postRequestParam(View view) {
        //先来okhttp客户端
        OkHttpClient okHttpClient = new OkHttpClient.Builder()
                .connectTimeout(8000, TimeUnit.MICROSECONDS).build();

        PostRequest request = new PostRequest();
        request.setUser_account("111");
        request.setUser_pwd("1111");
        Gson gson = new Gson();
        String jsonStr = gson.toJson(request);
        MediaType mediaType = MediaType.parse("application/json");

        RequestBody requestBody = RequestBody.create(jsonStr, mediaType);

        // 请求
        Request request1 = new Request.Builder()
                .post(requestBody)
                .url("http://172.20.10.2:8080/user/login")
                .build();
        // 返回数据的处理
        okHttpClient.newCall(request1).enqueue(new Callback() {
            @Override
            public void onResponse(@NonNull okhttp3.Call call, @NonNull Response response) throws IOException {
                System.out.println("111");
                Log.e(TAG, "onResponse: " + response.code());
                Log.e(TAG, "onResponse: " + response.body().string());
            }

            @Override
            public void onFailure(@NonNull okhttp3.Call call, @NonNull IOException e) {
                System.out.println("222");
                Log.e(TAG, "onFailure" + e.toString());
            }
        });
    }
}

4. postRequest.java. [这部分是post带参数需要的Bean 实体类]

package com.example.mainapp_bleda2.bean;

public class PostRequest {

    private String user_account;
    private String user_pwd;

    public String getUser_account() {
        return user_account;
    }

    public void setUser_account(String user_account) {
        this.user_account = user_account;
    }

    public String getUser_pwd() {
        return user_pwd;
    }

    public void setUser_pwd(String user_pwd) {
        this.user_pwd = user_pwd;
    }
}