当前位置：网站首页>2.0springmvc uses restful

2.0springmvc uses restful

2022-06-25 04:35:00 【gh-xiaohe】

List of articles

RESTful
RESTful Case study

author : gh-xiaohe
gh-xiaohe The blog of
If you think the blogger's article is good , I hope you'll make it three times in a row （ Focus on , give the thumbs-up , Comment on ）, Give me more support ！！！

RESTful

1、RESTful brief introduction

REST：Representational State Transfer, Presentation layer resource state transition .

a> resources

resources It is a kind of look Wait for the server The way , namely , Think of the server as composed of many discrete resources . Each resource is a nameable abstraction on the server . Because resource is an abstract concept , So it can not only represent a file in the server file system 、 A table in the database and so on , We can design resources as abstract as possible , As long as imagination allows and client application developers can understand . Similar to object-oriented design , Resources are organized around terms , The first concern is the noun . A resource can be made up of one or more URI To mark .URI Is the name of the resource , It's also resources Web Address on . Client applications interested in a resource , The URI Interact with it .

b> Expression of resources

The expression of resources is a paragraph about resources In a certain Specific moment Of state Of describe . Can be on the client side - Transfer between servers （ In exchange for ）. Resources can be expressed in a variety of formats , for example HTML/XML/JSON/ Pure text / picture / video / Audio and so on. . The presentation format of resources can be determined by negotiation mechanism . request - The response direction is usually expressed in different formats .

c> State shift

State transition is about ： stay client and Server side Between Transfer （transfer） Representation of resource status . By transferring and manipulating the expression of resources , To achieve the purpose of operating resources indirectly .

2、RESTful The implementation of the

specifically , Namely HTTP In the agreement , Four represent the operation mode It's a simple verb ：GET、POST、PUT、DELETE.

They correspond to four basic operations ：GET Used to obtain resources ,POST Used to create a new resource ,PUT Used to update resources ,DELETE Used to delete resources .

REST Style advocates URL Address using Unified style design , Use the words from front to back Slashes separate , Do not use question mark key values Carry on the way Request parameters , Instead, the data to be sent to the server is used as URL Part of the address , To ensure the consistency of the overall style .

operation	The traditional way	REST style
Query operation	getUserById?id=1	user/1–>get Request mode
Save operation	saveUser	user–>post Request mode
Delete operation	deleteUser?id=1	user/1–>delete Request mode
update operation	updateUser	user–>put Request mode

3、HiddenHttpMethodFilter filter

Because the browser only supports sending get and post Method request , So how to send put and delete What about the request ？

SpringMVC Provides HiddenHttpMethodFilter Help us take POST Request conversion to DELETE or PUT request

HiddenHttpMethodFilter Handle put and delete The condition of the request ：

Request mode of current request It has to be for post
The current request must be transmitted Request parameters _method

Meet the above conditions ,HiddenHttpMethodFilter The filter will convert the request mode of the current request into request parameters _method Value , So request parameters ==_method== The value of is the final request method

stay web.xml Register in HiddenHttpMethodFilter

<!-- Configure how requests are processed put and delete Of HiddenHttpMethodFilter-->
<filter>
    <filter-name>HiddenHttpMethodFilter</filter-name>
    <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
</filter>
<filter-mapping>
    <filter-name>HiddenHttpMethodFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

[ Failed to transfer the external chain picture , The origin station may have anti-theft chain mechanism , It is suggested to save the pictures and upload them directly (img-yCdaHbkm-1655820991011)(RESTful.assets/image-20220620214025581.png)]

Source code

/*  filter   There must be three ways  ① initialization （ important ） ② filtering  ③ Three methods of destruction   Mode one :  How to perform filtering doFilter Who has executed it   The subclass is not looking for the parent class   Mode two :  The search parameter is  filterChain  It must be the method of performing filtering  filterChain  For release  */ 
public class HiddenHttpMethodFilter extends OncePerRequestFilter {
    
    private static final List<String> ALLOWED_METHODS;
    public static final String DEFAULT_METHOD_PARAM = "_method";
    private String methodParam = "_method";

    public HiddenHttpMethodFilter() {
    
    }

    public void setMethodParam(String methodParam) {
    
        Assert.hasText(methodParam, "'methodParam' must not be empty");
        this.methodParam = methodParam;
    }

    // The search parameter is  filterChain  It must be the method of performing filtering  filterChain  For release  ( How to perform filtering )
    //HttpServletRequest request, HttpServletResponse response  Filtering is the interception of requests   and   Respond to 
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
    

        HttpServletRequest requestToUse = request; //  The assignment is  HttpServletRequest  object 

        //  Get request parameters   Is it equal to  POST  Constant for the  true
        if ("POST".equals(request.getMethod()) && request.getAttribute("javax.servlet.error.exception") == null) {
    
            //  Get request parameters  this.methodParam private String methodParam = "_method"; ( The value of a constant )
            String paramValue = request.getParameter(this.methodParam);
            if (StringUtils.hasLength(paramValue)) {
     //  Is there a length   Is it empty 
                String method = paramValue.toUpperCase(Locale.ENGLISH); //  take _method  Converts the value of to uppercase 
                if (ALLOWED_METHODS.contains(method)) {
     // Can only write  PUT DELETE PATCH  Here's the explanation 
                    // requestToUse  Assign him a value   Turned into  PUT DELETE PATCH
                    requestToUse = new HiddenHttpMethodFilter.HttpMethodRequestWrapper(request, method);
                }
            }
        }
        //  At the time of release   The newly created request object   As a   Filter intercepted objects   Released 
        filterChain.doFilter((ServletRequest)requestToUse, response);//  The results obtained in the future are  PUT DELETE PATCH
    }

    static {
    
        //List  combination  //  Put the last three values in list In combination  HttpMethod enumeration 
        ALLOWED_METHODS = Collections.unmodifiableList(Arrays.asList(HttpMethod.PUT.name(), HttpMethod.DELETE.name(), HttpMethod.PATCH.name()));
    }

    private static class HttpMethodRequestWrapper extends HttpServletRequestWrapper {
    
        private final String method;  // ② PUT DELETE PATCH

        public HttpMethodRequestWrapper(HttpServletRequest request, String method) {
    
            super(request);
            this.method = method; // ① PUT DELETE PATCH
        }

        public String getMethod() {
    
            return this.method; // ③ PUT DELETE PATCH
        }
    }
}

notes ：
When there are multiple filters , The order of filter execution is determined , The more advanced the configuration , Just execute

So far, ,SpringMVC Two filters are provided in ：CharacterEncodingFilter and HiddenHttpMethodFilter
stay web.xml Registration in China , Must first register CharacterEncodingFilter, To register again HiddenHttpMethodFilter
reason ：
stay CharacterEncodingFilter Pass through request.setCharacterEncoding(encoding) Method to set the value of the character set
request.setCharacterEncoding(encoding) Method requires that there must be no previous operation to get the request parameters
and HiddenHttpMethodFilter There is just one operation to get the request mode ：
String paramValue = request.getParameter(this.methodParam);

RESTful Case study

1、 preparation

And traditional CRUD equally , Realize the addition, deletion, modification and query of employee information .

Set up the environment

Prepare entity classes

public class Employee {
      

   private Integer id;
   private String lastName;

   private String email;
   //1 male, 0 female
   private Integer gender;
   
   public Integer getId() {
      
      return id;
   }

   public void setId(Integer id) {
      
      this.id = id;
   }

   public String getLastName() {
      
      return lastName;
   }

   public void setLastName(String lastName) {
      
      this.lastName = lastName;
   }

   public String getEmail() {
      
      return email;
   }

   public void setEmail(String email) {
      
      this.email = email;
   }

   public Integer getGender() {
      
      return gender;
   }

   public void setGender(Integer gender) {
      
      this.gender = gender;
   }

   public Employee(Integer id, String lastName, String email, Integer gender) {
      
      super();
      this.id = id;
      this.lastName = lastName;
      this.email = email;
      this.gender = gender;
   }

   public Employee() {
      
   }
}

Get ready dao Analog data

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

import com.atguigu.mvc.bean.Employee;
import org.springframework.stereotype.Repository;


@Repository // Persistent layer by layer component database 
public class EmployeeDao {
      

    private static Map<Integer, Employee> employees = null;

    static{
      
        employees = new HashMap<Integer, Employee>();

        employees.put(1001, new Employee(1001, "E-AA", "[email protected]", 1));
        employees.put(1002, new Employee(1002, "E-BB", "[email protected]", 1));
        employees.put(1003, new Employee(1003, "E-CC", "[email protected]", 0));
        employees.put(1004, new Employee(1004, "E-DD", "[email protected]", 0));
        employees.put(1005, new Employee(1005, "E-EE", "[email protected]", 1));
    }

    private static Integer initId = 1006;

    //  add to   and   modify   function 
    public void save(Employee employee){
      
        if(employee.getId() == null){
      
            employee.setId(initId++); //  Assign first   Increasing 
        }
        employees.put(employee.getId(), employee);
    }

    public Collection<Employee> getAll(){
      
        return employees.values();
    }

    public Employee get(Integer id){
      
        return employees.get(id);
    }

    public void delete(Integer id){
      
        employees.remove(id);
    }
}

2、 Feature list

function	URL Address	Request mode
Visit the home page √	/	GET
Query all data √	/employee	GET
Delete √	/employee/2	DELETE
Jump to the add data page √	/toAdd	GET
Perform save √	/employee	POST
Jump to the update data page √	/employee/2	GET
Perform the update √	/employee	PUT

3、 Specific function ： Visit the home page

a> To configure view-controller

<mvc:view-controller path="/" view-name="index"/>

b> Create a page

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8" >
    <title>Title</title>
</head>
<body>
<h1> home page </h1>
<a th:href="@{/employee}"> Access employee information </a>
</body>
</html>

4、 Specific function ： Query all employee data

a> Controller method

@RequestMapping(value = "/employee", method = RequestMethod.GET)
public String getEmployeeList(Model model){
    
    Collection<Employee> employeeList = employeeDao.getAll();
    model.addAttribute("employeeList", employeeList);
    return "employee_list";
}

b> establish employee_list.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Employee Info</title>
    <script type="text/javascript" th:src="@{/static/js/vue.js}"></script>
</head>
<body>
	<!-- Margin  = 1 ,  Cancel margins ,  Cancel spacing   In the middle -->
    <table border="1" cellpadding="0" cellspacing="0" style="text-align: center;" id="dataTable">
        <tr>
            <th colspan="5">Employee Info</th>
        </tr>
        <tr>
            <th>id</th>
            <th>lastName</th>
            <th>email</th>
            <th>gender</th>
            <th>options(<a th:href="@{/toAdd}">add</a>)</th>
        </tr>
        <tr th:each="employee : ${employeeList}">
            <td th:text="${employee.id}"></td>
            <td th:text="${employee.lastName}"></td>
            <td th:text="${employee.email}"></td>
            <td th:text="${employee.gender}"></td>
            <td>
                <!-- Wrong way of writing : {  It will be resolved to  %7B }  It will be resolved to  %7D-->
                <!--<a th:href="@{/employee/${employee.id}}">delete</a>-->
                <!-- Mode one :-->
                    <a @click="deleteEmployee" th:href="@{
     '/employee/'+${employee.id}}">delete</a>
                <!-- Mode two :-->
                    <a th:href="@{
     '/employee/'+${employee.id}}">update</a>
            </td>
        </tr>
    </table>
</body>
</html>

5、 Specific function ： Delete a key

a> Create processing delete Request Form

<!--  effect ： Control the submission of forms through hyperlinks , take post Request conversion to delete request  -->
<form id="delete_form" method="post">
    <!-- HiddenHttpMethodFilter requirement ： Must transmit _method Request parameters , And the value is the final request method  -->
    <input type="hidden" name="_method" value="delete"/>
</form>

b> Delete hyperlink binding click event

introduce vue.js

<script type="text/javascript" th:src="@{/static/js/vue.js}"></script>

Create hyperlinks

                <!-- Wrong way of writing : {  It will be resolved to  %7B }  It will be resolved to  %7D-->
                <!--<a th:href="@{/employee/${employee.id}}">delete</a>-->
                <!-- Mode one :-->
                    <a @click="deleteEmployee" th:href="@{
     '/employee/'+${employee.id}}">delete</a>
                <!-- Mode two :-->
                    <a th:href="@{
     '/employee/'+${employee.id}}">update</a>

adopt vue Handle click events

    <script type="text/javascript"> var vue = new Vue({
       el:"#dataTable", methods:{
       deleteEmployee:function (event) {
       // according to id Get form elements  var deleteForm = document.getElementById("deleteForm"); // The of the hyperlink that will trigger the click event href Property is assigned to the of the form action deleteForm.action = event.target.href; // Submit Form  deleteForm.submit(); // Cancel the default behavior of hyperlinks  event.preventDefault(); } } }); </script>

c> Controller method

@RequestMapping(value = "/employee/{id}", method = RequestMethod.DELETE)
public String deleteEmployee(@PathVariable("id") Integer id){
    
    employeeDao.delete(id);
    return "redirect:/employee";
}

6、 Specific function ： Jump to the add data page

a> To configure view-controller

<mvc:view-controller path="/toAdd" view-name="employee_add"></mvc:view-controller>

b> establish employee_add.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Add Employee</title>
</head>
<body>

<form th:action="@{/employee}" method="post">
    lastName:<input type="text" name="lastName"><br>
    email:<input type="text" name="email"><br>
    gender:<input type="radio" name="gender" value="1">male
    <input type="radio" name="gender" value="0">female<br>
    <input type="submit" value="add"><br>
</form>

</body>
</html>

* 7、 Specific function ： Perform save

a> Controller method

@RequestMapping(value = "/employee", method = RequestMethod.POST)
public String addEmployee(Employee employee){
    
    employeeDao.save(employee);
    return "redirect:/employee";
}

8、 Specific function ： Jump to the update data page

a> Modify hyperlinks

<a th:href="@{
     '/employee/'+${employee.id}}">update</a>

b> Controller method

@RequestMapping(value = "/employee/{id}", method = RequestMethod.GET)
public String getEmployeeById(@PathVariable("id") Integer id, Model model){
    
    Employee employee = employeeDao.get(id);
    model.addAttribute("employee", employee);
    return "employee_update";
}

c> establish employee_update.html

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <meta charset="UTF-8">
    <title>Update Employee</title>
</head>
<body>

<form th:action="@{/employee}" method="post">
    <input type="hidden" name="_method" value="put">
    <input type="hidden" name="id" th:value="${employee.id}"> <!-- The echo data ${}-->
    lastName:<input type="text" name="lastName" th:value="${employee.lastName}"><br>
    email:<input type="text" name="email" th:value="${employee.email}"><br>
    <!-- th:field="${employee.gender}" Can be used to echo radio boxes or check boxes   If the radio box value and employee.gender The value is consistent. , Then add checked="checked" attribute  -->
    gender:<input type="radio" name="gender" value="1" th:field="${employee.gender}">male
    <input type="radio" name="gender" value="0" th:field="${employee.gender}">female<br>
    <input type="submit" value="update"><br>
</form>

</body>
</html>

9、 Specific function ： Perform the update

a> Controller method

@RequestMapping(value = "/employee", method = RequestMethod.PUT)
public String updateEmployee(Employee employee){
    
    employeeDao.save(employee);
    return "redirect:/employee";
}