restful認為,每個資源都有自己唯一的資源定位符(URI),
  每個URI都代表了一種資源,以一張圖片為例:圖片有自己的路徑,
  所以圖片也是一種資源. 所以URI中不用動詞,只用名詞.
  一般數(shù)據(jù)庫的表都是記錄同種的集合,所以為名詞為復數(shù) 
  這就是為什么請求路徑中的操作資源要加 s ,
  可以不遵循這個規(guī)范(看自己喜歡或者公司規(guī)范)

新增 :從無到有
更新:從某個狀態(tài)變成另一個狀態(tài)
刪除 :從有到無    

員工列表查詢與員工單個查詢,使用相同映射路徑" /employees 和相同請求方法:RequestMethod.GET,
導致請求路徑(路徑+請求方法)一樣,報錯

restful提供解決方案:使用參數(shù)路徑方法
    參數(shù)路徑:將參數(shù)作為請求路徑的一部分  /employee/{id}       
    還要加上注解@PathVariable,將id拿到
        
瀏覽器/postman發(fā)起請求時使用:
   http://localhost:8080/employee/1 其中1是id參數(shù)值,同時也是請求路徑的一部分
  另外,請求映射方法必須使用@PathVariable 進行參數(shù)讀取
      
 注意: 如果路徑參數(shù)標記與請求參數(shù)名不一致時 ,怎么辦?
        可以使用@PathVariable("eid") value屬性指定

@Controller
public class EmployeeController {

    @RequestMapping(value = "employees",method = RequestMethod.GET)
    @ResponseBody
    public List<Employee> list(){
        List<Employee> employees = Arrays.asList(new Employee(1L, "小羅", 22), new Employee(2L, "小軒", 18));
        return  employees;
    }

    @RequestMapping(value = "employees/{id}",method = RequestMethod.GET)
    @ResponseBody
    public Employee get(@PathVariable Long id){
        List<Employee> employees = Arrays.asList(new Employee(1L, "xxx", 22), new Employee(2L, "qqq", 22));
        return employees.get((int) (id-1));
    }

    @RequestMapping(value = "employees",method = RequestMethod.POST)
    @ResponseBody
    public Employee save(Employee employee){
        employee.setId(1L);
        return employee ;
    }
    
    @RequestMapping(value = "employees",method = RequestMethod.DELETE)
    @ResponseBody
    public JsonResult delete(Long id){
        return new JsonResult(true,"刪除成功");

    }
    @RequestMapping(value = "employees",method = RequestMethod.PUT)
    @ResponseBody
    public JsonResult update(Long id){
        return new JsonResult(true,"更新成功");

    }
}

參數(shù)路徑方式:
   優(yōu)點:可以隱藏參數(shù),避免暴露參數(shù),相對安全
   缺點:如果參數(shù)較多,url過長 不建議使用            
   參數(shù)較少選用參數(shù)路徑方法   

Accept：application/json :代表客戶端希望接受得數(shù)據(jù)類型是json類型,后臺返回json數(shù)據(jù)
Content-Type：application/json:代表發(fā)送端發(fā)送數(shù)據(jù)格式是json,后臺要以這種格式類接收前端的數(shù)據(jù)    

刪除,更新操作
    $.ajax({
        url:  路徑   ,
        type:  類型  ,
        data: 參數(shù){id:111},
        success:(回調(diào)函數(shù))function(data){
            
        }
    })

<script>
        $(function () {
    		//查全部
            $("#btn1").click(function () {
                $.get("/employees" ,function (data) {
                    console.log(data);
                })
            });
			//查單個
            $("#btn2").click(function () {
                $.get("/employees/1" ,function (data) {
                    console.log(data);
                })
            });

			//新增
            $("#btn4").click(function () {
                $.post("/employees" ,{name:"xiao",age:18},function (data) {
                    console.log(data);
                })
            });
			//刪除
            $("#btn3").click(function () {
                $.ajax({
                    url:"/employees",
                    type: "DELETE",
                    data:{id:1},
                    success:function (data) {
                        console.log(data);
                    }
                })
            });

			//更新
            $("#btn5").click(function () {
                $.ajax({
                    url:"/employees",
                    type: "PUT",
                    data:{id:1},
                    success:function (data) {
                        console.log(data);
                    }
                })
            })
        })
    </script>

<filter>
	<filter-name>httpPutFormContentFilter</filter-name>
	<filter-class>org.springframework.web.filter.HttpPutFormContentFilter</filter-class>
</filter>

<filter-mapping>
	<filter-name>httpPutFormContentFilter</filter-name>
	<servlet-name>springMVC</servlet-name>
</filter-mapping>

等價于 method =RequestMethod.GET|POST|DELETE|PUT

等價于 @Controller +@ResponseBody	

params :要求請求中必須攜帶指定名稱的參數(shù)    
          params="name" :必須攜帶name參數(shù)
          params="name=xuan" :必須攜帶name參數(shù),并且name=xuan 
    
 headers :請求頭，限定要處理請求的請求頭信息，只有匹配才會被方法處理
    
consume :等價于Content-Type  
value/path：映射路徑
method：限定請求的方式   

@RestController
@RequestMapping("employees")
public class EmployeeController {

    @GetMapping
    public List<Employee> list(){
        List<Employee> employees = Arrays.asList(new Employee(1L, "小羅", 22), new Employee(2L, "小軒", 18));
        return  employees;
    }

    @GetMapping(value = "/{id}")
    public Employee get(@PathVariable Long id){
        List<Employee> employees = Arrays.asList(new Employee(1L, "xxx", 22), new Employee(2L, "qqq", 22));
        return employees.get((int) (id-1));
    }

    @PostMapping
    public Employee save(Employee employee){
        employee.setId(1L);
        return employee ;
    }

    @DeleteMapping
    public JsonResult delete(Long id){
        return new JsonResult(true,"刪除成功");
    }

    @PutMapping
    public JsonResult update(Long id){
        return new JsonResult(true,"更新成功");
    }
}