Spring Boot之 Controller 接收参数和返回数据总结(包括上传、下载文件)

一、接收参数（postman发送）

1.form表单

@RequestParam("name") String name

会把传递过来的Form表单中的name对应到formData方法的name参数上

该注解不能接收json传参

该注解表示name字段是必须入参的，否则会报错

@RequestParam(value = "name", required = false) String name

required = false表示必须入参

@RequestParam(value = "name", defaultValue = "admin") String name

defaultValue = "admin"表示当name入参为空的时候给它一个默认值admin

    /**

     * 测试接收form表单、URL的数据。不能接收Json数据

     * */

    @RequestMapping(value = "/test1", method = RequestMethod.POST)

    public String formData(@RequestParam("name") String name , @RequestParam("age") int age){

        String result = "receive name = "+name+" age = "+age;

        System.out.println(result);

        return result;

    }

2.URL

代码跟1.form表单中的代码一样

3.动态接收URL中的数据

@PathVariable将URL中的占位符参数绑定到控制器处理方法的入参

此种情况下，url求情中一定要带占位符pageNo,pageSize的值，不然访问失败

即访问时一定要用 http://localhost:8088/sid/test2/2/20

如果用 http://localhost:8088/sid/test2 则访问失败

    /**

     * 测试动态接收URL中的数据

     * */

    @RequestMapping(value = "/test2/{pageNo}/{pageSize}", method = RequestMethod.POST)

    public String urlData(@PathVariable int pageNo , @PathVariable int pageSize){

        String result = "receive pageNo = "+pageNo+" pageSize = "+pageSize;

        System.out.println(result);

        return result;

    }

4.json

@RequestBody 接收Json格式的数据需要加这个注解。该注解不能接收URL、Form表单传参

    /**

     * 测试接收json数据

     * */

    @RequestMapping(value = "/jsonData", method = RequestMethod.POST)

    public String jsonData(@RequestBody TestModel tm){

        String result = "receive name = "+tm.getName()+" age = "+tm.getAge();

        System.out.println(result);

        return result;

    }

5.@RequestMapping注解详细介绍

1.处理多个URL

@RestController  

@RequestMapping("/home")  

public class IndexController {  

    @RequestMapping(value = {  

        "",  

        "/page",  

        "page*",  

        "view/*,**/msg"  

    })  

    String indexMultipleMapping() {  

        return "Hello from index multiple mapping.";  

    }  

} 

这些 URL 都会由 indexMultipleMapping() 来处理： 

localhost:8080/home

localhost:8080/home/

localhost:8080/home/page

localhost:8080/home/pageabc

localhost:8080/home/view/

localhost:8080/home/view/view

2.HTTP的各种方法

如POST方法

@RequestMapping(value = "/test1", method = RequestMethod.POST)

3.produces、consumes 

produces 指定返回的内容类型，仅当request请求头header中的(Accept)类型中包含该指定类型才返回。结合@ResponseBody使用
---------------------

@Controller
@RequestMapping(value = "/t")
public class TestController {

    //方法仅处理request请求中Accept头中包含了"text/html"的请求
    @ResponseBody
    @RequestMapping(value = "/produces",produces = {"text/html"})
    public String testProduces(String name)
    {
        return "test requestMapping produces attribute! "+name;
    }
}

方法仅处理request请求中Accept头中包含了"text/html"的请求

比如用postman构建一个Accept=“application/json”的请求，请求会失败

comsumes  指定处理请求的提交内容类型（Content-Type），例如application/json, text/html。结合@RequestBody使用

@Controller
@RequestMapping(value = "/t")
public class TestController {

    //方法仅处理request Content-Type为"application/json"类型的请求
    @ResponseBody
    @RequestMapping(value = "/consumes",consumes = {"application/json"})
    public String testConsumes(@RequestBody String name)
    {
        return "test requestMapping consumes attribute! "+name;
    }
}

方法仅处理request Content-Type为"application/json"类型的请求。

如果用postman构建一个Content-Type=“application/x-www-form-urlencoded”的请求，该方法不处理

4.headers 

根据请求中的消息头内容缩小请求映射的范围

例如：

只处理header中testHeader = sid的请求

    //方法仅处理header中testHeader = sid的请求
    @ResponseBody
    @RequestMapping(value = "/header",headers = {"testHeader = sid"})
    public String testHeader(String name)
    {
        return "test requestMapping headers attribute! "+name;
    }

构建一个header钟不带testHeader=sid的请求，会失败

必须要header中带testHeader=sid的请求的请求才处理

5.结合params属性处理请求参数

例如：

请求参数name=sid的时候由getParams方法处理

请求参数name=lee的时候由getParamsDifferent方法处理

@Controller
@RequestMapping(value = "/t")
public class TestController {

    @RequestMapping(value = "/params", params = {
            "name=sid"
    })
    @ResponseBody
    public String getParams(@RequestParam("name") String name) {
        return "getParams method do " + name;
    }
    @RequestMapping(value = "/params", params = {
            "name=lee"
    })
    @ResponseBody
    public String getParamsDifferent(@RequestParam("name") String name) {
        return "getParamsDifferent method do  " + name;
    }
}

二、返回值
@RestController注解，相当于@Controller+@ResponseBody两个注解的结合，返回json数据不需要在方法前面加@ResponseBody注解了，但使用@RestController这个注解，就不能返回jsp,html页面，视图解析器无法解析jsp,html页面

1.返回静态html页面
application.yml
---------------------

server:
  port: 8088
  servlet:
    context-path: /sid

spring:
  mvc:
   view:
    prefix: /
    suffix: .html

    /**
     * 返回界面 index.html
     * @Controller修饰的类 直接定义方法返回值为String
     * */
    @RequestMapping(value = "/index")
    public String index(){

        return "index";
    }

    /**返回界面 index.html
     * @RestController修饰的类  
     * 需要配合视图解析器    
     * */
    @RequestMapping("/indexmv")
    public ModelAndView indexmv() {
        ModelAndView mv = new ModelAndView("index");
        return mv;
    }

2.通过object返回查询结果

@ResponseBody会把返回值变成json

    /**
     * 直接查询得到的model类，@ResponseBody会把返回值变成json
     * */
    @RequestMapping(value = "/object", method = RequestMethod.POST)
    @ResponseBody
    public Object object(@RequestParam("name") String name , @RequestParam("age") String age){

        TestModel t =getModel( name , age);
        List<TestModel> list =new ArrayList();
        list.add(t);
        return list;
    }

3.返回时直接抛出自定义异常

    /**
     * 返回时直接抛出自定义异常
     * */
    @RequestMapping(value = "/list", method = RequestMethod.POST)
    @ResponseBody
    public List<TestModel> list(@RequestParam("name") String name , @RequestParam("age") String age){
        TestModel t =getModel( name , age);

        if(t != null){
            throw new MyException("测试抛出自定义异常");
        }
        List<TestModel> list =new ArrayList();
        list.add(t);
        list.add(t);
        return list;
    }

4.返回ResponseEntity

两种不同的创建ResponseEntity的方式

 /**
     * 返回ResponseEntity
     *
     * ResponseEntity的优先级高于@ResponseBody。
     * 在不是ResponseEntity的情况下才去检查有没有@ResponseBody注解。
     * 如果响应类型是ResponseEntity可以不写@ResponseBody注解
     * */
    @RequestMapping(value = "/responseEntity", method = RequestMethod.POST)
    public ResponseEntity<?> responseEntity(@RequestParam("name") String name , @RequestParam("age") String age){

        try{
            TestModel t =getModel( name , age);
            if(!t.getAge().equals("27")){
                throw new MyException("年龄错误！");
            }
            List<TestModel> list =new ArrayList();
            list.add(t);
            list.add(t);
            HttpHeaders headers = new HttpHeaders();
            //headers.set("Content-type", "application/json;charset=UTF-8");
            headers.add("code", "1");
            headers.add("msg", "success");
            headers.add("error", "");
            return new ResponseEntity<List>(list,headers,HttpStatus.OK);
        }catch (MyException e){
            return ResponseEntity.badRequest()
                    //.header("Content-type", "application/json;charset=UTF-8")
                    .header("code", "0")
                    .header("msg", "")
                    .header("error", e.getMessage())//中文乱码
                    .build();//build无返回值 body有返回值
        }
    }

--------------------------------------

5.返回自定义类，其中有code msg error data 而查询结果在data中

MyResponse.java

package com.sid.springtboot.test.springboottest;

public class MyResponse<T> {
    private String code;
    private String msg;
    private String error;
    private T data;

    public MyResponse(String code, String msg, String error, T data) {
        this.code = code;
        this.msg = msg;
        this.error = error;
        this.data = data;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public String getError() {
        return error;
    }

    public void setError(String error) {
        this.error = error;
    }

    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }
}

MyException.java

package com.sid.springtboot.test.springboottest;

public class MyException extends RuntimeException{

    private String errorCode;
    private String msg;

    public MyException(String message) {
        super(message);
    }

    public MyException(String errorCode, String msg) {
        this.errorCode = errorCode;
        this.msg = msg;
    }

    public String getErrorCode() {
        return errorCode;
    }

    public void setErrorCode(String errorCode) {
        this.errorCode = errorCode;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }
}

controller

 /**
     * 返回自定义类，其中有code msg error data 而查询结果在data中
     * */
    @RequestMapping(value = "/myResponse", method = RequestMethod.POST)
    @ResponseBody
    public MyResponse<?> myResponse(@RequestParam("name") String name , @RequestParam("age") String age){
        try{
            TestModel t1 =getModel( name , age);
            if(!t1.getAge().equals("27")){
                throw new MyException("年龄错误！");
            }
            List<TestModel> list =new ArrayList();
            list.add(t1);
            list.add(t1);
            list.add(t1);
            return new MyResponse<List>("1","success",null,list);
        }catch (MyException e){
            return new MyResponse<>("0",null,e.getMessage(),null);
        }
    }

三、上传、下载文件

上传文件

    @PostMapping("/upload")
    @ResponseBody
    public Map<String, String> upload1(@RequestParam("file") MultipartFile file) throws IOException {
        System.out.println("[文件类型] - [{}]"+ file.getContentType());
        System.out.println("[文件名称] - [{}]"+ file.getOriginalFilename());
        System.out.println("[文件大小] - [{}]"+ file.getSize());
        //保存
        file.transferTo(new File("D:\\gitrep\\springboot\\testFile\\" + file.getOriginalFilename()));
        Map<String, String> result = new HashMap<>(16);
        result.put("contentType", file.getContentType());
        result.put("fileName", file.getOriginalFilename());
        result.put("fileSize", file.getSize() + "");
        return result;
    }

下载文件

1.通过ResponseEntity<InputStreamResource>实现

封装ResponseEntity，将文件流写入body中。这里注意一点，就是文件的格式需要根据具体文件的类型来设置，一般默认为application/octet-stream。文件头中设置缓存，以及文件的名字。文件的名字写入了，都可以避免出现文件随机产生名字，而不能识别的问题。
---------------------

@GetMapping("/download")
    public ResponseEntity<InputStreamResource> downloadFile() throws IOException {
        String filePath = "D:\\gitrep\\springboot\\testFile\\" + "api-ms-win-core-console-l1-1-0.dll";
        FileSystemResource file = new FileSystemResource(filePath);
        HttpHeaders headers = new HttpHeaders();
        headers.add("Cache-Control", "no-cache, no-store, must-revalidate");
        headers.add("Content-Disposition", String.format("attachment; filename=\"%s\"", file.getFilename()));
        headers.add("Pragma", "no-cache");
        headers.add("Expires", "0");

        return ResponseEntity.ok().headers(headers)
                .contentLength(file.contentLength())
                .contentType(MediaType.parseMediaType("application/octet-stream"))
                .body(new InputStreamResource(file.getInputStream()));
    }

2.用HttpServletResponse

@GetMapping("/download2")
    public String downloadFile2( HttpServletResponse response) throws IOException {
        // 获取指定目录下的文件
        String fileName = "D:\\gitrep\\springboot\\testFile\\" + "api-ms-win-core-console-l1-1-0.dll";
        File file = new File(fileName);
        // 如果文件名存在，则进行下载
        if (file.exists()) {
            // 配置文件下载
            response.setHeader("content-type", "application/octet-stream");
            response.setContentType("application/octet-stream");
            // 下载文件能正常显示中文
            response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));

            // 实现文件下载
            byte[] buffer = new byte[1024];
            FileInputStream fis = null;
            BufferedInputStream bis = null;
            try {
                fis = new FileInputStream(file);
                bis = new BufferedInputStream(fis);
                OutputStream os = response.getOutputStream();
                int i = bis.read(buffer);
                while (i != -1) {
                    os.write(buffer, 0, i);
                    i = bis.read(buffer);
                }
                System.out.println("Download the song successfully!");
            }
            catch (Exception e) {
                System.out.println("Download the song failed!");
            } finally {
                if (bis != null) {
                    try {
                        bis.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                if (fis != null) {
                    try {
                        fis.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return null;
    }