7. Spring Boot Controller

7.1. 理解 Controller

@Controller vs @RestController

@RestController = @Controller + @ResponseBody

7.2. 实现REST服务

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@RestController
public class HelloWorldController {
    @Autowired
    private IHelloWorldService helloWorldService;

    @GetMapping("/hello")
    public String hello(String name) {
        return helloWorldService.getHelloMessage(name);
    }
}

@Service
public class HelloWorldServiceImpl implements IHelloWorldService {

    public String getHelloMessage(String name) {
        return "Hello " + Optional.ofNullable(name).orElse("World!");
    }

}

7.3. ResponseEntity

https://www.baeldung.com/spring-response-entity

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@GetMapping("/hello")
ResponseEntity<String> hello() {
    return ResponseEntity.ok("Hello World!");
}

7.4. RequestMapping

RequestMapping route 有多种方式。

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package com.example.demo.controller;

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    @GetMapping("/hello")
    ResponseEntity<String> hello() {
        return ResponseEntity.ok("Hello World!");
    }

    @GetMapping({ "/hello2", "hello3" })
    ResponseEntity<String> hello2() {
        return ResponseEntity.ok("Hello World!");
    }

    @GetMapping(value = "/hello3", headers = "key=val")
    ResponseEntity<String> hello3() {
        return ResponseEntity.ok("Hello World!");
    }

    @GetMapping(value = "/hello4", headers = { "key1=val1", "key2=val2" })
    ResponseEntity<String> hello4() {
        return ResponseEntity.ok("Hello World!");
    }

    @GetMapping(value = "/hello5", headers = "Accept=application/json")
    ResponseEntity<String> hello5() {
        return ResponseEntity.ok("Hello World!");
    }

    @GetMapping(value = "/hello6", produces = "application/json")
    String hello6() {
        return "Hello World!";
    }

}

测试

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curl -i http://localhost:8080/hello
curl -i -H "key:val" http://localhost:8080/hello3
curl -i -H "key1:val1" -H "key2:val2" http://localhost:8080/hello4
curl -H "Accept:application/json,text/html" http://localhost:8080/hello5

7.5. Controller中获取参数

7.5.1. Controller方法的形参

直接把表单的参数写在Controller相应的方法的形参中，适用于get方式提交，不适用于post方式提交。

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/**
* 1.直接把表单的参数写在Controller相应的方法的形参中
* @param username
* @param password
* @return
*/
@RequestMapping("/addUser1")
public String addUser1(String username,String password) {
    System.out.println("username is:"+username);
    System.out.println("password is:"+password);
    return "demo/index";
}

url形式：http://localhost/demo/addUser1?username=training&password=111111 提交的参数需要和Controller方法中的入参名称一致。

7.5.2. HttpServletRequest

通过HttpServletRequest接收，post方式和get方式都可以。

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/**
* 2、通过HttpServletRequest接收
* @param request
* @return
*/
@RequestMapping("/addUser2")
public String addUser2(HttpServletRequest request) {
    String username=request.getParameter("username");
    String password=request.getParameter("password");
    System.out.println("username is:"+username);
    System.out.println("password is:"+password);
    return "demo/index";
}

7.5.3. 通过Bean接收

通过一个bean来接收,post方式和get方式都可以。

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/**
* 3、通过一个bean来接收
* @param user
* @return
*/
@RequestMapping("/addUser3")
public String addUser3(UserModel user) {
    System.out.println("username is:"+user.getUsername());
    System.out.println("password is:"+user.getPassword());
    return "demo/index";
}

7.5.4. @PathVariable

通过@PathVariable获取路径中的参数

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@RestController
@RequestMapping(value="/users")
public class MyRestController {

    @RequestMapping(value="/{user}", method=RequestMethod.GET)
    public User getUser(@PathVariable Long user) {
        // ...
    }

    @RequestMapping(value="/{user}/customers", method=RequestMethod.GET)
    List<Customer> getUserCustomers(@PathVariable Long user) {
        // ...
    }

    @RequestMapping(value="/{user}", method=RequestMethod.DELETE)
    public User deleteUser(@PathVariable Long user) {
        // ...
    }

}

7.5.5. @ModelAttribute

使用@ModelAttribute注解获取POST请求的FORM表单数据

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<!--jsp页面-->
<form action ="<%=request.getContextPath()%>/demo/addUser5" method="post">
    用户名:<input type="text" name="username"/><br/>
    密码:<input type="password" name="password"/><br/>
    <input type="submit" value="提交"/> <input type="reset" value="重置"/>
</form>

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/**
* 5、使用@ModelAttribute注解获取POST请求的FORM表单数据
* @param user
* @return
*/
@RequestMapping(value="/addUser5",method=RequestMethod.POST)
public String addUser5(@ModelAttribute("user") UserModel user) {
    System.out.println("username is:"+user.getUsername());
    System.out.println("password is:"+user.getPassword());
    return "demo/index";
}

7.5.6. @RequestParam

用注解@RequestParam绑定请求参数到方法入参

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@GetMapping("/demo/{id}")
public void demo(@PathVariable(name = "id") String id, @RequestParam(name = "name") String name) {
    System.out.println("id="+id);
    System.out.println("name="+name);
}

当请求参数username不存在时会有异常发生,可以通过设置属性required=false解决,例如: @RequestParam(value=”username”, required=false)

7.5.7. @RequestBody

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@PostMapping(path = "/demo1")
public void demo1(@RequestBody Person person) {
    System.out.println(person.toString());
}

前端JSON传值，@RequestBody 也可以省略

7.5.8. @RequestHeader @CookieValue

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@GetMapping("/demo3")
public void demo3(@RequestHeader(name = "myHeader") String myHeader,
        @CookieValue(name = "myCookie") String myCookie) {
    System.out.println("myHeader=" + myHeader);
    System.out.println("myCookie=" + myCookie);
}

/**
* 8、上面的代码等同下面的代码
*/
@GetMapping("/demo3")
public void demo3(HttpServletRequest request) {
    System.out.println(request.getHeader("myHeader"));
    for (Cookie cookie : request.getCookies()) {
        if ("myCookie".equals(cookie.getName())) {
            System.out.println(cookie.getValue());
        }
    }
}