Article catalog
- 1, Response data and results view
- 2, Spring MVC file upload
- 3, Spring MVC exception handling
- 4, Spring MVC interceptor
1, Response data and results view
Dark horse programmer spring MVC Day2 part
1.1 return value classification
1.1.1 return string
import cn.gorit.entity.User;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
@Controller
@RequestMapping("/user")
public class UserController {
// Return string
@RequestMapping("/testString")
public String testString(Model model) {
System.out.println("testString Yes");
User user = new User(); // Entity class User
user.setUsername("to one's heart's content");
user.setPassword("123321");
user.setAge(18);
model.addAttribute("user",user);
return "success";
}
}
// After the previous processing by the view parser, you will jump to the success.jsp interface
<h5>1, Return string</h5>
full name: ${user.username}</br>
password: ${user.password}</br>
Age: ${user.age}1.1.2 return void
/**
* Returns null. If there is no return value,
* testVoid.jsp will be requested by default, and the result is 404
* Request forwarding is a request
* Redirection is two requests
*/
@RequestMapping("/testVoid")
public void testVoid(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("testVoid Yes");
// 1. Prepare the procedure for request forwarding
// request.getRequestDispatcher("/WEB-INF/pages/success.jsp").forward(request,response);
// 2. Redirection
// response.sendRedirect("../index.jsp");
// 3. Direct corresponding
PrintWriter out = response.getWriter();
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("gbk"); // Solve Chinese garbled code
response.setContentType("text/html;charset=gbk");
out.print("Hello");
out.flush();
out.close();
return;
}1.1.3 the return value is ModelAndView object
// Is consistent with the returned string
@RequestMapping("/testModelAndView")
public ModelAndView testModelAndView() {
System.out.println("testModelAndView Yes");
//Spring provides
ModelAndView mv = new ModelAndView();
User user = new User();
user.setUsername("breeze");
user.setPassword("456");
user.setAge(18);
// Storing the user object in the mv object will also store the user object in the request object
mv.addObject("user",user);
// Which page to jump to
mv.setViewName("success");
return mv;
}1.2 forwarding and redirection
/**
* Forward or redirect using keywords
* */
@RequestMapping("/testForwardOrRedirect")
public String testForwardOrRedirect() {
System.out.println("testForwardOrRedirect Yes");
// Forwarding of requests
// return "forward:/WEB-INF/pages/success.jsp";
// Redirect (return to root)
return "redirect:/index.jsp";
}1.3 ajax response json string
- Add json parsing dependency in pom.xml
<dependency>
<groupId>com.fasterxml.jackson.coregroupId>
<artifactId>jackson-databindartifactId>
<version>2.10.0version>
dependency>
<dependency>
<groupId>com.fasterxml.jackson.coregroupId>
<artifactId>jackson-coreartifactId>
<version>2.10.0version>
dependency>
<dependency>
<groupId>com.fasterxml.jackson.coregroupId>
<artifactId>jackson-annotationsartifactId>
<version>2.10.0version>
dependency>- Writing front-end ajax requests
<button id="btn">send out ajax</button>
<script type="text/javascript">
// Page loading, binding click events
$(function () {
$("#btn").click(function () {
// alert("Hello");
$.ajax({
url:"user/testAjax",
type:"post",
contentType:"application/json;charset=UTF-8",
data:'{"username":"hehe","password":"122","age":30}', // Transfer json data
dataType:"json",
success:function (data) {
// Data is the json data responded by the server, which is parsed
alert(data);
alert(data.username);
alert(data.password);
alert(data.age);
}
})
})
})
</script>- ajax response (back-end processing)
// Simulate asynchronous request response
@RequestMapping("/testAjax")
public @ResponseBody User testAjax(@RequestBody User user) {
System.out.println("testAjax Yes");
// The ajax request sent by the client is received, and the json string is passed. The back-end encapsulates the json string into the user object
System.out.println(user);
// Get the json string and process {"username":"hehe","password":"122","age:30} accordingly
// Respond and simulate query database
user.setUsername("hehe");
user.setAge(40);
// Respond
return user;
}2, Spring MVC file upload
2.1 file upload
- Prerequisites for file upload
2.2 uploading files in traditional way
Upload dependent jar packages
<dependency>
<groupId>commons-fileuploadgroupId>
<artifactId>commons-fileuploadartifactId>
<version>1.3.3version>
dependency>
<dependency>
<groupId>commons-iogroupId>
<artifactId>commons-ioartifactId>
<version>2.5version>
dependency>fileFile upload front end code
<h3>File upload h3>
<form action="user/fileupload1" method="post" enctype="multipart/form-data">
<input type="file" name="upload"/><br>
<input type="submit" value="upload">
form>Backend controller
@Controller
@RequestMapping("/user")
public class UserController {
@RequestMapping("/fileupload1")
public String fileUpload(HttpServletRequest request) throws Exception {
System.out.println("File upload...");
// Use fileupload to complete file upload
String path = request.getSession().getServletContext().getRealPath("/uploads/");
// Determine whether the path exists
File file = new File(path);
if (!file.exists()) {
// Create this folder
file.mkdirs();
}
// Parse the request object to obtain the uploaded file item
DiskFileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory);
// Parse request
List<FileItem> items = upload.parseRequest(request);
// ergodic
for (FileItem item: items) {
// Judge whether the current item object is an uploaded file item
if (item.isFormField()) {
// Normal form items
} else {
// Upload file item
// Gets the name of the uploaded file
String fileName = item.getName();
// Set each file name to a unique value, uuid
String uuid = UUID.randomUUID().toString().replace("-","");
fileName = uuid +"_"+ fileName;
// Complete file upload
item.write(new File(path,fileName));
// Delete temporary file
item.delete();
}
}
return "success";
}
}2.3 file upload provided by spring MVC
Upload principle
Front page
<h3>File upload SpringMVCh3>
<form action="user/fileupload2" method="post" enctype="multipart/form-data">
<input type="file" name="upload"/><br>
<input type="submit" value="upload">
form>Springmvc.xml
Add a file parser
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<property name="maxUploadSize" value="10240" />
bean>Written by controller
// Spring MVC file upload
@RequestMapping("/fileupload2")
public String fileupload2(HttpServletRequest request, MultipartFile upload) throws Exception {
System.out.println("File upload...");
// Use fileupload to complete file upload
String path = request.getSession().getServletContext().getRealPath("/uploads/");
// Determine whether the path exists
File file = new File(path);
if (!file.exists()) {
// Create this folder
file.mkdirs();
}
// Upload file item
// Gets the name of the uploaded file
String fileName = upload.getOriginalFilename();
// Set each file name to a unique value, uuid
String uuid = UUID.randomUUID().toString().replace("-","");
fileName = uuid +"_"+ fileName;
// Complete file upload
upload.transferTo(new File(path,fileName));
return "success";
}2.4 cross server file upload
Add a jar package, open two Tomcat servers, and upload files across servers using different ports
3, Spring MVC exception handling
3.1 exception handling ideas
3.2 handling exceptions
I don't know why I always report 500 errors here
- Write a custom exception class (for prompt information)
- Write exception handler
- Configure exception handler (jump to display page)
Front jump page
<h3>exception handling h3>
<a href="user/testException">exception handling a>Exception handling controller writing
@Controller
@RequestMapping("/user")
public class UserController {
// exception handling
@RequestMapping("/testException")
public String testException() throws SysException {
System.out.println("testException. . . ");
try {
// Simulation anomaly
int a = 10/0;
} catch (Exception e) {
// Print exception information
e.printStackTrace();
// Throw custom exception information
throw new SysException("An error occurred for all users queried");
}
return "success";
}
}Custom exception handler
package cn.gorit.exception;
import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Exception handler
* */
public class SysExceptionResolver implements HandlerExceptionResolver {
/**
* Business logic for handling exceptions
* */
@Override
public ModelAndView resolveException(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
// Get exception object
SysException e = null;
if (ex instanceof SysException) {
e = (SysException)ex;
} else {
e = new SysException("The system is being maintained");
}
// Create ModelAndView object
ModelAndView mv = new ModelAndView();
mv.addObject("errorMsg", e.getMessage());
mv.setViewName("error"); // To jump to the page, remember to write an error.jsp under WEB-INF/pages
return mv;
}
}package cn.gorit.exception;
/**
* Custom exception class
* */
public class SysException extends Exception{
// Storage prompt new
private String message;
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
public SysException(String message) {
this.message = message;
}
}springmvc.xml configuration
<bean id="sysExceptionResolver" class="cn.gorit.exception.SysExceptionResolver">bean>
4, Spring MVC interceptor
4.1 interceptor function
4.2 writing interceptors
4.3 interceptor preparation
- Front end interface jump
<h3>Interceptor h3>
<a href="test/testIntercepter">Interceptor a>- Written by back-end controller
package cn.gorit.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
@RequestMapping("/test")
public class TestController {
/**
* Interceptor
* */
@RequestMapping("/testIntercepter")
public String testIntercepter() {
System.out.println("testIntercepter. . . ");
return "success";
}
}- Interceptor class writing
package cn.gorit.interceptor;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* custom interceptor
* */
public class MyInterceptor implements HandlerInterceptor {
/**
* Pretreatment
* return true Indicates release, and executes the next interceptor. If not, executes the controller method
* */
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
System.out.println("The interceptor executed");
return true;
}
/**
* Post processing method, after the controller method is executed and before the success.jsp is executed
* */
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
System.out.println("The interceptor executed,succes.jsp Before loading");
}
/**
* success.jsp If executed, the method will execute
* */
@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
System.out.println("The interceptor executed success.jsp after");
}
}- Interceptor springmvc.xml configuration
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:component-scan base-package="cn.gorit">context:component-scan>
<bean id="internalResourceViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/pages/">property>
<property name="suffix" value=".jsp">property>
bean>
<mvc:resources mapping="/js/**" location="/js/">mvc:resources>
<mvc:resources mapping="/css/**" location="/csss/">mvc:resources>
<mvc:resources mapping="/images/**" location="/images/">mvc:resources>
<mvc:interceptors>
<mvc:interceptor>
<mvc:mapping path="/**"/>
<bean class="cn.gorit.interceptor.MyInterceptor">bean>
mvc:interceptor>
mvc:interceptors>
<mvc:annotation-driven/>
beans>Operation effect
