Learning objectives
1,Interceptor 2,File upload and download 3,RESTFul
1. Interceptor
1.1 interceptor concept
Similar to the Filter filter in Java Web, it is used to Filter requests and intercept requests that do not meet the requirements
Difference between interceptor and filter:
1) Filters are more widely used than interceptors, which can be used by Java Web projects. Interceptors can only be used in spring MVC
2) Interceptor efficiency higher than filter
1.2 use of interceptors
1) Implement the HandlerInterceptor interface
2) Implementation method
-
preHandle preprocessing
-
postHandle post processing
-
afterCompletion post processing
/**
* Login interceptor
*/
public class LoginInterceptor implements HandlerInterceptor {
/**
* Preprocessing
*/
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
//Query whether the session saves the user
User user = (User) request.getSession().getAttribute("user");
if(user == null){
//No login, redirect to login page
response.sendRedirect("/pages/login");
//Return false to intercept
return false;
}
//Return true and release
return true;
}
}
3) Configure interceptor
<!--Configuring Interceptors -->
<mvc:interceptors>
<mvc:interceptor>
<!--Configure intercepted URL Request path /**Represents all requests -- >
<mvc:mapping path="/**"/>
<!--Configure request paths that are not intercepted -- >
<mvc:exclude-mapping path="/**/login"/>
<mvc:exclude-mapping path="/**/*.css"/>
<mvc:exclude-mapping path="/**/*.js"/>
<mvc:exclude-mapping path="/**/*.png"/>
<mvc:exclude-mapping path="/**/*.jpg"/>
<!--to configure class-->
<bean class="com.blb.bookms.interceptor.LoginInterceptor"/>
</mvc:interceptor>
</mvc:interceptors>
2. File upload and download
2.1 file upload
There are two ways to upload files:
-
Traditional Servlet file upload
-
Spring MVC file upload
2.1.1 traditional Servlet file upload
1) Import dependency
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.4</version>
</dependency>
2) Write form
Three elements of form file upload:
- Add enctype = "multipart / form data" to the form tag
- The submission method is post
- The input type is file
<form action="/upload" method="post" enctype="multipart/form-data">
...
<input type="file" name="file" >
...
</form>
2) Upload method
@Controller
public class UploadController {
@RequestMapping("/upload")
public String fileupload(HttpServletRequest request) throws Exception {
//Get the upload directory path of the project
String path= request.getSession().getServletContext().getRealPath("/upload/");
File file=new File(path);
//Determine whether the folder exists
if (!file.exists()){
//create folder
file.mkdirs();
}
//Create upload object
ServletFileUpload upload=new ServletFileUpload(new DiskFileItemFactory());
//Get file list
List<FileItem> fileItems= upload.parseRequest(request);
for (FileItem item:fileItems){
//Determine whether the file is an ordinary form item
if (item.isFormField()){
//If it is a normal form item, print the form item name and value
System.out.println(item.getFieldName());
System.out.println(item.getString());
}else{
//If it is a file, intercept the suffix
String filename= item.getName();
String suffix = filename.substring(filename.lastIndexOf("."));
//Create a unique file name
String uuid= UUID.randomUUID().toString().replace("-","");
filename = uuid + suffix;
//Complete file upload
item.write(new File(path,filename));
System.out.println("Upload complete");
}
}
//Jump to success page
return "success";
}
2.1.2 spring MVC file upload
The dependency form is the same as above
The MultipartFile parameter is used in the upload method to obtain the uploaded file
@RequestMapping("/upload")
public String fileupload(HttpServletRequest request, MultipartFile upload) throws Exception {
//Get the upload directory path under the project directory
String path = request.getSession().getServletContext().getRealPath("/upload/");
System.out.println(path);
File file = new File(path);
if (!file.exists()) {
file.mkdirs();
}
//Get the name of the uploaded file
String filename = upload.getOriginalFilename();
String suffix = filename.substring(filename.lastIndexOf("."));
//Create a unique file name
String uuid= UUID.randomUUID().toString().replace("-","");
filename = uuid + suffix;
//Complete file upload
upload.transferTo(new File(path,filename));
return "success";
}
You need to add an upload processor to the spring MVC configuration
<!--Upload processor-->
<bean class="org.springframework.web.multipart.commons.CommonsMultipartResolver" id="multipartResolver">
<!--Maximum bytes of uploaded file-->
<property name="maxUploadSize" value="10485760"/>
</bean>
2.1.3 spring MVC multi file upload
Add multiple file items to the form
<form action="/upload" method="post" enctype="multipart/form-data">
<input type="file" name="uploads">
<input type="file" name="uploads">
<input type="file" name="uploads">
<input type="submit" value="MVC Multi file upload">
</form>
Add MultipartFile array as parameter, and the parameter name is consistent with the form name
@RequestMapping("/upload3")
public String fileupload3(HttpServletRequest request, MultipartFile[] uploads) throws Exception {
//Get the upload directory path under the tomcat project directory
String path = request.getSession().getServletContext().getRealPath("/upload/");
System.out.println(path);
File file = new File(path);
if (!file.exists()) {
file.mkdirs();
}
for(MultipartFile upload : uploads) {
//Get the name of the uploaded file
String filename = upload.getOriginalFilename();
String suffix = filename.substring(filename.lastIndexOf("."));
//Create a unique file name
String uuid = UUID.randomUUID().toString().replace("-", "");
filename = uuid + "-" + suffix;
//Complete file upload
upload.transferTo(new File(path, filename));
}
return "success";
}
2.1.4 other upload classes of spring MVC
Spring MVC also provides other API s to support uploading:
- CommonsMultipartResolver multipart resolver is used to determine whether there is an uploaded file in the request
- MultipartHttpServletRequest is a multipart request used to obtain file related information
Specific usage:
@RequestMapping("upload4")
public String fileupload4(HttpServletRequest request) throws IllegalStateException, IOException
{
String path = request.getSession().getServletContext().getRealPath("/upload/");
//Create multipart parser
CommonsMultipartResolver multipartResolver=new CommonsMultipartResolver(
request.getSession().getServletContext());
//Check whether the form supports file upload
if(multipartResolver.isMultipart(request)){
//Convert the request into multi part request and support uploading
MultipartHttpServletRequest multiRequest=(MultipartHttpServletRequest)request;
//Gets all the file names in the request
Iterator iter=multiRequest.getFileNames();
while(iter.hasNext()) {
//Traverse all files
MultipartFile file=multiRequest.getFile(iter.next().toString());
if(file!=null) {
//Get the name of the uploaded file
String filename = file.getOriginalFilename();
String suffix = filename.substring(filename.lastIndexOf("."));
//Create a unique file name
String uuid = UUID.randomUUID().toString().replace("-", "");
filename = uuid + suffix;
//upload
file.transferTo(new File(path,filename));
}
}
}
return "success";
}
2.2 file download
/**
* Download controller
*/
@Controller
public class DownloadController {
@RequestMapping("download")
public void download(String file, HttpServletResponse response) throws IOException {
//Path to download file
String path = "D:\\install\\";
File downFile = new File(path+file);
if(downFile.exists()){
//Set browser download content type, response header
response.setContentType("application/x-msdownload");
response.setHeader("Content-Disposition","attachment;filename="+file);
//Send files by streaming
Files.copy(downFile.toPath(),response.getOutputStream());
}
}
}
3,RestFul
3.1 front and rear end separation
3.1.1 what is the front and rear end separation
Front end projects (html5, applet, mobile terminal) and back-end projects (java, database, tomcat) are developed and deployed separately
3.1.2 front and rear end separation advantages
1) The development division of labor is clear, and the front-end team and back-end team work together at the same time
2) The project deploys different servers separately. For example, Tomcat is suitable for deploying dynamic resources and Nginx is suitable for deploying static resources
3) Easy to test and maintain
3.1.3 interaction mode of front and rear end developers
1) Designers design interfaces according to requirements and provide interface documents
1) The back-end develops the background interface according to the interface document
2) The front end requests data through the interface and renders the page
3.2 RESTFul
3.2.1 what is restful
RESTFul is a design style and development method of network applications. It is based on HTTP and can be defined in XML format or JSON format. It is applicable to the scenario where the mobile Internet manufacturer acts as a service enabling interface to realize the function of a third party calling mobile network resources. The action types are adding, changing and deleting the called resources.
RESTful architecture is the most popular Internet software architecture. It has clear structure, conforms to standards, is easy to understand and easy to expand, so it is being adopted by more and more websites.
3.2.2 characteristics of restful architecture
-
Each URI corresponds to a resource (database data, method, etc.) on the server
-
Add, delete, modify and query operations are distinguished through different Http request methods
-
Get -- > query
-
Post -- > Add
-
Put -- > Update
-
Delete -- > delete
- The format of communication is JSON
3.2.3 RESTFul style API
In traditional API design, verbs are often used to define APIs, such as find, get, save, update, delete, etc
Query all books: http://Domain name / book/findAll Query a Book: http://Domain name / book/findById?id=1 Add books: http://Domain name / book/saveBook Update books: http://Domain name / book/updateBook Delete book: http://Domain name / book/deleteBook?id=1
RESTFul style API design uses only nouns and different request methods to distinguish addition, deletion, modification and query
Query all books: GET http://Domain name / books Query a Book: GET http://Domain name / book/1 Add books: POST http://Domain name / book Update books: PUT http://Domain name / book Delete book: DELETE http://Domain name / book/1
Implementation of Restful style controller
@RestController defines a RestFul style controller, in which all methods directly return data, which is equivalent to adding @ ResponseBody
@RestController
public class BookController {
@Autowired
private BookService bookService;
@GetMapping("/books")
public JsonResult findAll(){
try {
List<Book> list = bookService.list();
return new JsonResult(1,list);
}catch (Exception ex){
ex.printStackTrace();
return new JsonResult(0,null);
}
}
@GetMapping("/book/{id}")
public JsonResult findById(@PathVariable("id")Integer id){
try {
Book book = bookService.getById(id);
return new JsonResult(1,book);
}catch (Exception ex){
ex.printStackTrace();
return new JsonResult(0,null);
}
}
@PostMapping("/book")
public JsonResult saveBook(@RequestBody Book book){
try {
bookService.save(book);
return new JsonResult(1,null);
}catch (Exception ex){
ex.printStackTrace();
return new JsonResult(0,null);
}
}
@PutMapping("/book")
public JsonResult updateBook(@RequestBody Book book){
try {
bookService.updateById(book);
return new JsonResult(1,null);
}catch (Exception ex){
ex.printStackTrace();
return new JsonResult(0,null);
}
}
@DeleteMapping("/book/{id}")
public JsonResult delBook(@PathVariable("id")Integer id){
try {
bookService.removeById(id);
return new JsonResult(1,null);
}catch (Exception ex){
ex.printStackTrace();
return new JsonResult(0,null);
}
}
}
3.2.4 the browser supports DELETE and PUT
By default, the browser only supports GET and POST requests. If you want the form to submit DELETE or PUT requests, you need to implement it through the spring MVC filter
web.xml add:
<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>
HiddenHttpMethodFilter is used to filter the form named_ The hidden field of method. If the value is DELETE, the request method will be converted to DELETE, and if it is PUT, the request method will be converted to PUT.
form
<form action="/testDelete" method="post">
<input name="name" placeholder="Enter name"><br>
<input type="hidden" name="_method" value="DELETE"/>
<input type="submit" value="Submit">
</form>