后端Spring Boot+前端Android交互+MySQL增删查改

大鹏一日同风起，扶摇直上九万里。这篇文章主要讲述后端Spring Boot+前端Android交互+MySQL增删查改相关的知识，希望能为你提供帮助。
2020.06.23 更新 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 = "https://www.songbingjia.com/android/select * from user where name = ?1",nativeQuery = true) public List< User> findByName(String name); @Modifying @Query(value = "https://www.songbingjia.com/android/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& lt; E& gt;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;

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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 UIUI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

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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‘ }