后端Spring Boot+前端Android交互+MySQL增刪查改

2021.1.27 更新

已更新新版本博客，更新內容很多，因此新開了一篇博客，戳這里。

1 概述

使用spring boot作為后端框架與Android端配合mysql進行基本的交互,包含了最基本的增刪查改功能.

2 開發環境

• Win
• IDEA 2019.2
• Tomcat 9.0.27
• MySQL 8.0.17
• Spring Boot 2.2.1
• JDK 8

3 后端

3.1 新建一個Spring Boot項目

參考這里.

3.2 實體類

新建User類作為實體類:

@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;
    }
}

用的其實是3.1鏈接中的代碼,里面有詳細的解釋.

3.3 持久層

新建UserRepository實現增刪查改:

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

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

由於CrudRepository中已經包含了"增"與"改",所以按需要實現自己的"查"與"刪"即可.
CrudRepository的api很簡單,官方文檔在這里.

• "增"使用save即可,參數為實體類
• "刪"使用deleteById,通過主鍵刪除,若不想通過主鍵刪除可以自己編寫sql,像上面一樣
• "查"使用findAll或findById,自定義查找的話需要自己編寫SQL
• "改"也可使用save,注意需要設置主鍵

@Query用於設置SQL語句,nativeQuery表示使用原生SQL.

3.4 業務層

新建一個MainService.java:

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

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

    public List<User> 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<E>類型
• findByName():根據name返回所有name相同的行
• add直接使用了save,由於save返回的是實體類,原本的代碼是這樣寫的:

return userRepository.save(user) != null;

但是文檔說了不會為null,所以只能強制返回true了.

• modify使用了id與name作為參數,新建一個user,將其作為setter的參數,然后交給save
• deleteByName使用了自定義的刪除函數,返回的是int,在UserRepository中這個int代表SQL影響的行數,刪除成功則行數不為0,刪除失敗,或者沒有這行數據則行數為0.因此將返回值與0進行比較

3.5 控制層

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

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

    @PostMapping(path = "/get")
    public @ResponseBody List<User> 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主要就是幾個注解,除了getAllUsers使用Get外,其他的都是用Post.另外就是路徑設置,直接在path中設置即可.
后端的話到這里就基本完成了,剩下的打包部署操作就不說了,需要的可以參考這里.

4 Android端

什么新建工程之類的就不說了.
貼上部分MainActivity,完整代碼見文末:

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        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, "注冊成功", Toast.LENGTH_SHORT).show();
                }
                else
                {
                    Toast.makeText(this, "注冊失敗", Toast.LENGTH_SHORT).show();
                }
                Looper.loop();
            }
            //...
		}).start();});
		
        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<User> users = JSONArray.parseArray(response.body().string(),User.class);
                Looper.prepare();
                if(users.size() == 0)
                {
                    Toast.makeText(this,"登錄失敗",Toast.LENGTH_SHORT).show();
                }
                else
                {
                    Toast.makeText(this,"登錄成功",Toast.LENGTH_SHORT).show();
                }
                Looper.loop();
            }
            //...
		}).start();});

        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, "刪除成功", Toast.LENGTH_SHORT).show();
                }
                else
                {
                    Toast.makeText(this, "刪除失敗", Toast.LENGTH_SHORT).show();
                }
                Looper.loop();
            }
            //...
		}).start();});
		
        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, "修改失敗", Toast.LENGTH_SHORT).show();
                }
                Looper.loop();
            }
            //...
		}).start();});
    }
}

下面分別進行CRUD操作.

4.1 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, "注冊成功", Toast.LENGTH_SHORT).show();
    }
    else
    {
        Toast.makeText(this, "注冊失敗", Toast.LENGTH_SHORT).show();
    }
    Looper.loop();
} catch (IOException e) {
    e.printStackTrace();
}

使用OkHttp,通過FormBody設置參數,然后創建Request通過OkHttpClient發送.
由於后端"增"的方法返回的是一個true,因此這里將response.body().string()轉換成boolean判斷是否操作成功.
稍微提一下,

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

這兩行可以在非UI線程中使用Toast.

4.2 刪

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, "刪除成功", Toast.LENGTH_SHORT).show();
    }
    else
    {
        Toast.makeText(this, "刪除失敗", Toast.LENGTH_SHORT).show();
    }
    Looper.loop();
} catch (IOException e) {
    e.printStackTrace();
}

刪這部分也是差不多的,就是改一下url,然后....然后沒有了....好像很簡單的樣子?2333333

4.3 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<User> users = JSONArray.parseArray(response.body().string(),User.class);
    Looper.prepare();
    if(users.size() == 0)
    {
        Toast.makeText(this,"登錄失敗",Toast.LENGTH_SHORT).show();
    }
    else
    {
        Toast.makeText(this,"登錄成功",Toast.LENGTH_SHORT).show();
    }
    Looper.loop();
} catch (IOException e) {
    e.printStackTrace();
}

查這里注意一下后端返回的是List,這里借助阿里的fastjson轉換成List.

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

然后判斷有沒有的話就判斷長度是否為0即可.

4.4 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, "修改失敗", Toast.LENGTH_SHORT).show();
    }
    Looper.loop();
} catch (IOException e) {
    e.printStackTrace();
}

改的話只需一個額外的ID參數,在FormBody中add一個即可,不難.

4.5 UI

UI不詳細說了,就幾個簡單的Button,具體可以看代碼中的xml文件.

4.6 依賴與其他

注意一下依賴,還有設置java8.

compileOptions{
	sourceCompatibility=1.8
	targetCompatibility=1.8
}

dependencies{
	implementation 'com.squareup.okhttp3:okhttp:x.x.x'
	implementation 'com.alibaba:fastjson:x.x.x'
}

• OkHttp最新版本戳這里查看
• fastjson最新版本戳這里查看

4.7 網絡權限

這個筆者之前的文章有說,主要就是AndroidManifest.xml中的權限設置,請看這里.

5 測試

原始數據庫:

注冊一個:

看看數據庫:

測試登錄:

試試登錄一個不存在的:

修改:



最后是刪除:


刪除一個不存在的會刪除失敗.

6 源碼

• Github
• 碼雲
• CODE.CHINA

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