后端Spring Boot+前端Android交互+MySQL增删查改

2021.1.27 更新

已更新新版本博客，更新内容很多，因此新开了一篇博客，戳这里。

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.

2 开发环境

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

3 后端

3.1 新建一个Spring Boot项目

参考这里.

3.2 实体类

新建User类作为实体类:

@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;
    }
}

用的其实是3.1链接中的代码,里面有详细的解释.

3.3 持久层

新建UserRepository实现增删查改:

@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语句,nativeQuery表示使用原生SQL.

3.4 业务层

新建一个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>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

3.5 控制层

@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不说了,需要的可以参考这里.

4 Android端

什么新建工程之类的就不说了.

贴上部分MainActivity,完整代码见文末:

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, "注册成功", Toast.LENGTH_SHORT).show();
                }
                else
                {
                    Toast.makeText(this, "注册失败", 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,"登录失败",Toast.LENGTH_SHORT).show();
                }
                else
                {
                    Toast.makeText(this,"登录成功",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, "删除成功", Toast.LENGTH_SHORT).show();
                }
                else
                {
                    Toast.makeText(this, "删除失败", 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, "修改失败", Toast.LENGTH_SHORT).show();
                }
                Looper.loop();
            }
            //...
		}).start();});
    }
}

下面分别进行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.

4.2 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?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<User> 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.

4.4 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.

4.5 UI

UI不详细说了,就几个简单的Button,具体可以看代码中的xml文件.

4.6 依赖与其他

注意一下依赖,还有设置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最新版本戳这里查看
• fastjson最新版本戳这里查看

4.7 网络权限

这个笔者之前的文章有说,主要就是AndroidManifest.xml中的权限设置,请看这里.

5 测试

原始数据库:



注册一个:



看看数据库:



测试登录:



试试登录一个不存在的:



修改:







最后是删除:





删除一个不存在的会删除失败.

6 源码

• Github
• 码云
• CODE.CHINA

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