后端springboot+前端Android交互+mysq

1.概述

使用spring boot作为后端框架与Android端配合MySQL进行基本的交互,包含了最基本的增删查改功能.

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2.开发环境

win10
IDEA
tomcat9.0.27
mysql8.0.17
spring boot

3.后端

(1)新建一个spring boot项目

可以看这里

(2)Entity

新建User类作为实体类:

package com.test;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;
    private String name;

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

这里其实使用的是(1)中的代码,里面有详细的解释.

(3)Repository

新建UserRepository去实现增删查改:

package com.test;

import org.springframework.data.jpa.repository.Modifying;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.CrudRepository;
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Repository;
import org.springframework.web.bind.annotation.RequestParam;

import java.util.List;

@Repository
public interface UserRepository extends CrudRepository
{
    @Query(value = "select * from user where name = ?1",nativeQuery = true)
    public List findByName(String name);

    @Modifying
    @Query(value = "delete from user where name = ?1",nativeQuery = true)
    public int deleteByName(String name);
}

由于CrudRepository中已经包含了"增"与"改",所以按需要实现自己的"查"与"删"即可.
CrudRepository的api很简单,官方文档在这里.

"增"使用save即可,参数为实体类
"删"使用deleteById,通过主键删除,若不想通过主键删除可以自己编写sql,像上面一样
"查"使用findAll或findById,自定义查找的话需要自己编写sql.
"改"也可使用save,注意需要设置主键.

@Query用于设置sql,nativeQuery表示使用原生sql.

(4)Service

新建一个MainService.java

package com.test;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import javax.transaction.Transactional;
import java.util.List;

@Transactional
@Service
public class MainService {
    @Autowired
    private UserRepository userRepository;

    public Iterable getAllUsers()
    {
        return userRepository.findAll();
    }

    public List findByName(String name)
    {
        return userRepository.findByName(name);
    }

    public boolean add(String name)
    {
        User user = new User();
        user.setName(name);
        userRepository.save(user);
        return true;
    }

    public boolean modify(Integer id,String name)
    {
        User user = new User();
        user.setName(name);
        user.setId(id);
        userRepository.save(user);
        return true;
    }

    public boolean deleteByName(String name)
    {
        return userRepository.deleteByName(name) != 0;
    }
}

getAllUsers()返回所有行,Iterable类型
findByName()根据name返回所有name相同的行.
add直接使用了save,由于save返回的是实体类,原本的代码是这样写的:
```
return userRepository.save(user) != null;
```
但是文档说了不会为null,所以只能强制返回true了.
modify使用了id与name作为参数,新建一个user,将其作为setter的参数,然后交给save.
deleteByName使用了自定义的删除函数,返回的是int,在UserRepository中这个int代表sql影响的行数,删除成功则行数不为0,删除失败,或者没有这行数据则行数为0.因此将返回值与0进行比较.

(5)Controller

package com.test;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@Controller
@RequestMapping(path = "/demo")
public class MainController {
    @Autowired
    private MainService mainService;

    @GetMapping(path = "/getAll")
    public @ResponseBody Iterable getAllUsers()
    {
        return mainService.getAllUsers();
    }

    @PostMapping(path = "/get")
    public @ResponseBody List findByName(String name)
    {
        return mainService.findByName(name);
    }

    @PostMapping(path = "/add")
    public @ResponseBody boolean add(@RequestParam String name)
    {
        return mainService.add(name);
    }

    @PostMapping(path = "/modify")
    public @ResponseBody boolean modify(@RequestParam Integer id,@RequestParam String name)
    {
        return mainService.modify(id,name);
    }

    @PostMapping(path = "/delete")
    public @ResponseBody boolean deleteByName(@RequestParam String name)
    {
        return mainService.deleteByName(name);
    }
}

Controller主要就是几个注解,除了getAllUsers使用Get外,其他的都是用Post.另外就是路径设置,直接在path中设置即可.
后端的话到这里就基本完成了,剩下的打包部署操作就.....

4.前端

什么新建工程之类的就不说了.
直接上MainActivity:

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.os.Looper;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.alibaba.fastjson.JSONArray;
import com.example.myapplication.model.dao.*;
import com.example.myapplication.model.entity.*;

import java.io.IOException;
import java.util.List;

import okhttp3.FormBody;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class MainActivity extends AppCompatActivity {

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

        Button register = findViewById(R.id.register);
        register.setOnClickListener(
                v ->
                {
                    new Thread(()-> {
                        OkHttpClient okHttpClient = new OkHttpClient();
                        String name = ((EditText) findViewById(R.id.name)).getText().toString();
                        FormBody formBody = new FormBody.Builder().add("name", name).build();
                        Request request = new Request.Builder()
                                .url(Constant.ADD)
                                .post(formBody)
                                .build();
                        try (Response response = okHttpClient.newCall(request).execute()) {
                            Looper.prepare();
                            if (Boolean.parseBoolean(response.body().string()))
                            {
                                Toast.makeText(this, "注册成功", Toast.LENGTH_SHORT).show();
                            }
                            else
                            {
                                Toast.makeText(this, "注册失败", Toast.LENGTH_SHORT).show();
                            }
                            Looper.loop();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }).start();
                }
        );
        Button login = findViewById(R.id.login);
        login.setOnClickListener(
                v ->
                {
                    new Thread(()-> {
                        OkHttpClient okHttpClient = new OkHttpClient();
                        String name = ((EditText) findViewById(R.id.name)).getText().toString();
                        FormBody formBody = new FormBody.Builder().add("name", name).build();
                        Request request = new Request.Builder()
                                .url(Constant.GET)
                                .post(formBody)
                                .build();
                        try (Response response = okHttpClient.newCall(request).execute()) {
                            List users = JSONArray.parseArray(response.body().string(),User.class);
                            Looper.prepare();
                            if(users.size() == 0)
                            {
                                Toast.makeText(this,"登录失败",Toast.LENGTH_SHORT).show();
                            }
                            else
                            {
                                Toast.makeText(this,"登录成功",Toast.LENGTH_SHORT).show();
                            }
                            Looper.loop();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }).start();
                }
        );

        Button delete = findViewById(R.id.delete);
        delete.setOnClickListener(
                v ->
                {
                    new Thread(()-> {
                        OkHttpClient okHttpClient = new OkHttpClient();
                        String name = ((EditText) findViewById(R.id.name)).getText().toString();
                        FormBody formBody = new FormBody.Builder().add("name", name).build();
                        Request request = new Request.Builder()
                                .url(Constant.DELETE)
                                .post(formBody)
                                .build();
                        try (Response response = okHttpClient.newCall(request).execute()) {
                            Looper.prepare();
                            if (Boolean.parseBoolean(response.body().string()))
                            {
                                Toast.makeText(this, "删除成功", Toast.LENGTH_SHORT).show();
                            }
                            else
                            {
                                Toast.makeText(this, "删除失败", Toast.LENGTH_SHORT).show();
                            }
                            Looper.loop();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }).start();
                }
        );

        Button modify = findViewById(R.id.modify);
        modify.setOnClickListener(
                v ->
                {
                    new Thread(()-> {
                        OkHttpClient okHttpClient = new OkHttpClient();
                        String name = ((EditText) findViewById(R.id.name)).getText().toString();
                        String id = ((EditText)findViewById(R.id.id)).getText().toString();
                        FormBody formBody = new FormBody.Builder()
                                .add("name", name)
                                .add("id",id)
                                .build();
                        Request request = new Request.Builder()
                                .url(Constant.MODIFY)
                                .post(formBody)
                                .build();
                        try (Response response = okHttpClient.newCall(request).execute()) {
                            Looper.prepare();
                            if (Boolean.parseBoolean(response.body().string()))
                            {
                                Toast.makeText(this, "修改成功", Toast.LENGTH_SHORT).show();
                            }
                            else
                            {
                                Toast.makeText(this, "修改失败", Toast.LENGTH_SHORT).show();
                            }
                            Looper.loop();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }).start();
                }
        );
    }
}

(1)增

OkHttpClient okHttpClient = new OkHttpClient();
String name = ((EditText) findViewById(R.id.name)).getText().toString();
FormBody formBody = new FormBody.Builder().add("name", name).build();
Request request = new Request.Builder()
        .url(Constant.ADD)
        .post(formBody)
        .build();
try (Response response = okHttpClient.newCall(request).execute()) {
    Looper.prepare();
    if (Boolean.parseBoolean(response.body().string()))
    {
        Toast.makeText(this, "注册成功", Toast.LENGTH_SHORT).show();
    }
    else
    {
        Toast.makeText(this, "注册失败", Toast.LENGTH_SHORT).show();
    }
    Looper.loop();
} catch (IOException e) {
    e.printStackTrace();
}

使用okhttp,通过FormBody设置参数,然后创建Request通过OkHttpClient发送.
由于后端"增"的方法返回的是一个true,因此这里将response.body().string()转换成boolean判断是否操作成功.
稍微提一下,

Looper.prepare();
Looper.loop();

这两行可以在非UI线程中使用Toast.

(2)删

OkHttpClient okHttpClient = new OkHttpClient();
String name = ((EditText) findViewById(R.id.name)).getText().toString();
FormBody formBody = new FormBody.Builder().add("name", name).build();
Request request = new Request.Builder()
        .url(Constant.DELETE)
        .post(formBody)
        .build();
try (Response response = okHttpClient.newCall(request).execute()) {
    Looper.prepare();
    if (Boolean.parseBoolean(response.body().string()))
    {
        Toast.makeText(this, "删除成功", Toast.LENGTH_SHORT).show();
    }
    else
    {
        Toast.makeText(this, "删除失败", Toast.LENGTH_SHORT).show();
    }
    Looper.loop();
} catch (IOException e) {
    e.printStackTrace();
}

删这部分也是差不多的,就是改一下url,然后....然后没有了....~~好像很简单的样子?~~

(3)查

OkHttpClient okHttpClient = new OkHttpClient();
String name = ((EditText) findViewById(R.id.name)).getText().toString();
FormBody formBody = new FormBody.Builder().add("name", name).build();
Request request = new Request.Builder()
        .url(Constant.GET)
        .post(formBody)
        .build();
try (Response response = okHttpClient.newCall(request).execute()) {
    List users = JSONArray.parseArray(response.body().string(),User.class);
    Looper.prepare();
    if(users.size() == 0)
    {
        Toast.makeText(this,"登录失败",Toast.LENGTH_SHORT).show();
    }
    else
    {
        Toast.makeText(this,"登录成功",Toast.LENGTH_SHORT).show();
    }
    Looper.loop();
} catch (IOException e) {
    e.printStackTrace();
}

查这里注意一下后端返回的是List,这里借助阿里的fastjson转换成List.

List users = JSONArray.parseArray(response.body().string(),User.class);

然后判断有没有的话就判断长度是否为0即可.

(4)改

OkHttpClient okHttpClient = new OkHttpClient();
String name = ((EditText) findViewById(R.id.name)).getText().toString();
String id = ((EditText)findViewById(R.id.id)).getText().toString();
FormBody formBody = new FormBody.Builder()
        .add("name", name)
        .add("id",id)
        .build();
Request request = new Request.Builder()
        .url(Constant.MODIFY)
        .post(formBody)
        .build();
try (Response response = okHttpClient.newCall(request).execute()) {
    Looper.prepare();
    if (Boolean.parseBoolean(response.body().string()))
    {
        Toast.makeText(this, "修改成功", Toast.LENGTH_SHORT).show();
    }
    else
    {
        Toast.makeText(this, "修改失败", Toast.LENGTH_SHORT).show();
    }
    Looper.loop();
} catch (IOException e) {
    e.printStackTrace();
}

改的话只需一个额外的ID参数,在FormBody中add一个即可,不难.