SSM-Springboot笔记（2）- SpringBoot常用开发技能

1 SpringBoot常用开发技能

1.1 项目架构

• 创建项⽬
• 配置启动类
• 建⽴对应的包，先建⽴这些包，其他⽤到再补充

controller
service
mapper
domain
utils

1.2 开发HTTP接⼝GET请求

GET请求
场景：⼀般的查询接⼝就是get请求
注解：@GetMapping = @RequestMapping(method = RequestMethod.GET)
⼀个顶两的注解

@GetMapping = @RequestMapping(method = RequestMethod.GET)
@PostMapping = @RequestMapping(method = RequestMethod.POST)
@PutMapping = @RequestMapping(method = RequestMethod.PUT)
@DeleteMapping = @RequestMapping(method = RequestMethod.DELETE)

示例：视频列表查询

• 实体类：Video

public class Vedio implements Serializable {private Integer id;private String title;private String summary;private Integer price;private String coverImg;private Date createTime;public Vedio() {}public Vedio(Integer id, String title) {this.id = id;this.title = title;this.createTime = new Date();}
// 省get、set、tostring方法

• mapper类：VideoMapper

@Repository
public class VideoMapper {private static Map<Integer, Vedio> videoMap = new HashMap<>();/*** 模拟数据*/static {videoMap.put(1, new Vedio(1 , "东邪西毒"));videoMap.put(2, new Vedio(2 , "精武英雄"));videoMap.put(3, new Vedio(3 , "霸王别姬"));videoMap.put(4, new Vedio(4 , "南极大冒险"));videoMap.put(5, new Vedio(5 , "变形金刚"));videoMap.put(6, new Vedio(6 , "流浪地球"));}// 获取视频列表public List<Vedio> listVideo() {List<Vedio> list = new LinkedList<>();list.addAll(videoMap.values());return list;}
}

• service类，包括接口和实现类
  接口类: VideoService

public interface VideoService {List<Vedio> listVideo();
}

实现类：VideoServiceImpl

@Service
public class VideoServiceImpl implements VideoService {@Autowired  // 自动注入VideoMapperprivate VideoMapper videoMapper;@Overridepublic List<Vedio> listVideo() {return videoMapper.listVideo();}
}

• Controller类：VideoController

@RestController
@RequestMapping("/app/v1/video")
public class VideoController {@Autowired  // 自动注入VideoService实现类private VideoService videoService;@RequestMapping("list")public Object getList() {return videoService.listVideo();}
}

测试：

• 启动程序

  .   ____          _            __ _ _/\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \\\/  ___)| |_)| | | | | || (_| |  ) ) ) )'  |____| .__|_| |_|_| |_\__, | / / / /=========|_|==============|___/=/_/_/_/:: Spring Boot ::                (v2.6.2)2022-01-12 14:11:05.388  INFO 20464 --- [           main] c.j.s.Springbootdemo2Application         : No active profile set, falling back to default profiles: default
2022-01-12 14:11:06.005  INFO 20464 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2022-01-12 14:11:06.011  INFO 20464 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2022-01-12 14:11:06.011  INFO 20464 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.56]
2022-01-12 14:11:06.068  INFO 20464 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2022-01-12 14:11:06.068  INFO 20464 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 646 ms
2022-01-12 14:11:06.315  INFO 20464 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2022-01-12 14:11:06.321  INFO 20464 --- [           main] c.j.s.Springbootdemo2Application         : Started Springbootdemo2Application in 1.198 seconds (JVM running for 1.959)

• 访问接口

1.3 制定统⼀接⼝返回协议

实际开发中通过⾃定义返回对象，统⼀协议，能够有效的避免开发中协议不统一导致的许多问题，而且还能提供工作的效率。

• 自定义返回信息对象（务必生成get、set方法）

/*** 业务返回信息类*/
public class RetData {/*** 业务返回码，默认：0：成功，-1：失败*/private int code;   // 业务返回码/*** 业务数据*/private Object data;    // 业务数据/*** 返回信息*/private String message; // 状态信息public RetData(){}public RetData(int code, Object data, String message) {this.code = code;this.data = data;this.message = message;}/*** 无参返回成功，默认返回码*/public static RetData RetSuccess() {return new RetData(0, null, "success");}/*** 有参返回成功，默认返回码* @param data* @return*/public static RetData RetSuccess(Object data) {return new RetData(0, data, "success");}/*** 无参返回错误，默认返回码* @return*/public static RetData RetError() {return new RetData(-1, null, "unknow error");}/*** 默认返回码带错误信息* @param msg* @return*/public static RetData RetError(String msg) {return new RetData(-1, null, msg);}/*** 自定义返回码带错误信息* @param code* @param msg* @return*/public static RetData RetError(int code, String msg) {return new RetData(code, null, msg);}public int getCode() {return code;}public void setCode(int code) {this.code = code;}public Object getData() {return data;}public void setData(Object data) {this.data = data;}public String getMessage() {return message;}public void setMessage(String message) {this.message = message;}
}

• 在VideoController类中使用RetData返回

    @RequestMapping("list")public Object getList() {return RetData.RetSuccess(videoService.listVideo()); // 使用RetData返回}

• 重启程序并访问接口，返回结果如下：
  code：业务返回码
  data：业务数据
  message：返回信息

{"code": 0,"data": [{"id": 1,"title": "东邪西毒","summary": null,"price": null,"coverImg": null,"createTime": "2022-01-12T06:43:36.907+00:00"},{"id": 2,"title": "精武英雄","summary": null,"price": null,"coverImg": null,"createTime": "2022-01-12T06:43:36.907+00:00"},{"id": 3,"title": "霸王别姬","summary": null,"price": null,"coverImg": null,"createTime": "2022-01-12T06:43:36.907+00:00"},{"id": 4,"title": "南极大冒险","summary": null,"price": null,"coverImg": null,"createTime": "2022-01-12T06:43:36.907+00:00"},{"id": 5,"title": "变形金刚","summary": null,"price": null,"coverImg": null,"createTime": "2022-01-12T06:43:36.907+00:00"},{"id": 6,"title": "流浪地球","summary": null,"price": null,"coverImg": null,"createTime": "2022-01-12T06:43:36.907+00:00"}],"message": "success"
}

1.4 开发HTTP接⼝POST请求

POST请求-form表单
场景：表单提交，如果不⽤细分PUT/DELETE⽅法，则都可以⽤POST
注解：@PostMapping = @RequestMapping(method = RequestMethod.POST)
测试：

• 编写UserController类

@RestController
@RequestMapping("/app/v1/user")
public class UserController {@PostMapping("login")public RetData login(String username, String pwd) {System.out.println("username:" + username + ",pwd:" + pwd);return RetData.RetSuccess("");}
}

• 启动程序
• 采用参数形式

能够正常接收post提交的参数

• 采用form表单形式

也能够正常接收post提交的参数

实际开发中，参数数量比较多，通常我们会用对象接收参数，修改UserController如下：

@RestController
@RequestMapping("/app/v1/user")
public class UserController {@PostMapping("login")public RetData login(User user) {System.out.println("user:" + user.toString());return RetData.RetSuccess("");}
}

再次使用form表达形式提交

程序依然能够正常接收post提交的参数

user:User{id=null, username='tom', password='8888'}

但实际开发中，接口一般都是以json形式提交参数，提交方式如下：

此时程序无法正常接收数据

user:User{id=null, username='null', password='null'}

为了正常接收json形式的参数，需要在对象参数前面加注解：@RequestBody
注意：参数名字与对象属性名称保持一致

    @PostMapping("login")public RetData login(@RequestBody User user) {System.out.println("user:" + user.toString());return RetData.RetSuccess("");}

这样才能正常的接收

user:User{id=null, username='fanny', password='123456'}

开发示例：账号密码提交登录接⼝，form表单形式

• Mapper类：UserMapper

@Repository
public class UserMapper {private static Map<String, User> userMap = new HashMap<>();static {userMap.put("jackyan", new User(1, "jackyan", "123456"));userMap.put("lucy", new User(2, "lucy", "888888"));userMap.put("tom", new User(3, "tom", "666666"));userMap.put("fancy", new User(4, "fancy", "555555"));}public User login(String username, String password) {User user = userMap.get(username);if (user == null) {return null;} else if (user.getPassword().equals(password)) {return user;}return null;}
}

• Service类
  接口类：UserService

public interface UserService {public String login(String username, String password);
}

实现类：

@Service
public class UserServiceImpl implements UserService {// 模拟保存用户sessionprivate static Map<String, User> sessionMap = new HashMap<>();@Autowiredprivate UserMapper userMapper;@Overridepublic String login(String username, String password) {User user = userMapper.login(username, password);if (user == null) {return null;}String token = UUID.randomUUID().toString();// 保存用户sessionsessionMap.put(token, user);return token;}
}

• Controller类：UserController

@RestController
@RequestMapping("/app/v1/user")
public class UserController {@Autowiredprivate UserService userService;@PostMapping("login")public RetData login(@RequestBody User user) {String token = userService.login(user.getUsername(), user.getPassword());if (token == null) {return RetData.RetError("用户名或密码错误！");}return RetData.RetSuccess(token);}
}

• 测试

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登录失败

1.5 RequestBody对象数组提交接⼝

POST请求-RequestBody⽅式
开发示例：新增视频json对象，章数组提交

• Video类增加章列表信息

    private List<Chapter> chapterList;

• 新增Chapter类

/*** 视频章信息*/
public class Chapter {private Integer id;private Integer videoId;private String title;public Chapter() {}public Chapter(Integer id, Integer videoId, String title) {this.id = id;this.videoId = videoId;this.title = title;}
// 省略set、get、tostring方法

• 编写Controller类测试

    @PostMapping("save_video")public RetData saveVideo(@RequestBody Video video) {return RetData.RetSuccess(video);}

• 测试，发送数据

{"id":1001,"title":"精武英雄","chapterList":[{"id":10001,"title": "日本求学"},{"id":10002,"title": "回国探师"},{"id":10003,"title": "比武切磋"}]
}

• 测试结果

{"code": 0,"data": {"id": 1001,"title": "精武英雄","summary": null,"price": null,"coverImg": null,"createTime": null,"chapterList": [{"id": 10001,"videoId": null,"title": "日本求学"},{"id": 10002,"videoId": null,"title": "回国探师"},{"id": 10003,"videoId": null,"title": "比武切磋"}]},"message": "success"
}

1.6 定制JSON字段

springboot中自带jackson相关包，可以用来定制化处理实体类字段相关信息：
指定字段不返回：@JsonIgnore
指定⽇期格式：@JsonFormat(pattern="yyyy-MM-dd hh:mm:ss",locale="zh",timezone="GMT+8")
空字段不返回：@JsonInclude(Include.NON_NULL)
指定别名：@JsonProperty

    @JsonProperty("cover_img") // 给字段取别名private String coverImg;@JsonFormat(pattern="yyyy-MM-dd hh:mm:ss",locale="zh",timezone="GMT+8")@JsonProperty("create_time")private Date createTime;@JsonProperty("chapter_list")

    @JsonIgnore // 该字段不返回private String password;