Table of contents
1. Use Servlet native objects to obtain parameters
2. Custom parameter type converter
2.1 Write a type converter class
2.2 Register type converter object
Related readings of previous columns & articles
4. Spring MVC series of columns
1. Use Servlet native objects to obtain parameters
SpringMVC also supports the use of Servlet native objects, and parameters of types such as HttpServletRequest, HttpServletResponse, and HttpSession can be directly used in the method by defining parameters such as HttpServletRequest and HttpServletResponse in the method parameters.
1.1 Controller methods
// 使用Servlet原生对象
@RequestMapping("c1/param8")
public void servletParam(HttpSession session,HttpServletRequest request, HttpServletResponse response){
// 原生对象获取参数
System.out.println(request.getParameter("name"));
System.out.println(response.getCharacterEncoding());
System.out.println(session.getId());
}This is a very classic use of the request built-in object to obtain parameters. After the request, the parameters and encoding methods are printed on the console, as well as the corresponding sessionId.
Access path: http://localhost:8080/c1/param8?name=LYL
1.2 Test results
OK, it can be seen that the parameter value, encoding method and sessionId have been successfully queried
In general, there are alternatives to the methods of Servlet native objects in SpringMVC, and it is recommended to use SpringMVC instead of Servlet native objects.
2. Custom parameter type converter
The parameters from the front end are all of string type, and SpringMVC uses its own converter to convert the string parameters to the required type. like:
// Get simple type parameters @RequestMapping("/c1/param1") public void simpleParam(String username,int age){ System.out.println(username+" "+age); }But in some cases, the string cannot be converted to the required type, such as:
// Custom conversion date format string
@RequestMapping("c1/param9")
public void dataParam(Date birthday){ System.out.println(birthday); } Now let's test to see what the result is:
Console output:
Reason for error:
[WARNING]Resolved[org.springframework.web.method.annotation.MethodArgumentTypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'java.util.Date'; nested exception is org.springframework.core. convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [java.util.Date] for value '2025-01-01'; nested exception is java.lang.IllegalArgumentException] The
specific meaning is: [org .springframework.web.method.annotation.MethodArgumentTypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'java.util.Date'; nested exception is org.springfframework.core.covert. ConversionFailedException: Unable to convert value '2025-01-01' from type [java.lang.SString] to type [java.util.Date]; nested exception is java.lang.IllegalArgumentException]
2.1 Write a type converter class
Since there are many formats of date data, SpringMVC cannot convert strings in all formats into date types. For example, when the parameter format is birthday=2025-01-01, SpringMVC cannot parse the parameter. In this case a custom parameter type converter is required. First, you must define a type converter class and implement the Converter interface. It is written as follows:
package com.example.converter;
import org.springframework.core.convert.converter.Converter;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class DataConverter implements Converter<String, Date> {
/**
* 转换方法
* @param s 转换前的数据
* @return 转换后的数据
*/
@Override
public Date convert(String s) {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-mm-dd");
Date date = null;
try{
date = sdf.parse(s);
} catch (ParseException e) {
System.out.println("转换成日期格式出错了！");
e.printStackTrace();
}
return date;
}
}
2.2 Register type converter object
<!-- 配置转换器工厂 -->
<bean id="dateConverter" class="org.springframework.context.support.ConversionServiceFactoryBean">
<!-- 转换器集合 -->
<property name="converters">
<set>
<!-- 自定义转换器 -->
<bean class="com.example.converter.DataConverter"></bean>
</set>
</property>
</bean>
<!-- 使用转换器工厂 -->
<mvc:annotation-driven conversion-service="dateConverter"></mvc:annotation-driven>
OK, after adding the above, let's run the test again to see if the control can be successfully received
2.3 Test results
You can see that the 404 error was reported, and this page was not found, instead of 400
OK, the console is also successfully printed out.
3. Encoding filter
When passing parameters, tomcat8 and above can handle the Chinese garbled characters of the get request, but cannot handle the Chinese garbled characters of the post request
3.1 JSP form
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>专属页面</title>
</head>
<body>
<form action="/c1/param3" method="post">
<table>
<tr>
<th>id:</th>
<td><input name="id"/></td>
</tr>
<tr>
<th>姓名：</th>
<td><input name="name"/></td>
</tr>
<tr>
<th>性别：</th>
<td><input name="sex"/></td>
</tr>
<tr>
<th>住址：</th>
<td><input name="address.info"/></td>
</tr>
<tr>
<th>邮编：</th>
<td><input name="address.postcode"/></td>
</tr>
<tr align="center">
<td><input type="submit"/></td>
</tr>
</table>
</form>
</body>
</html>
Here is a form submission page
3.2 Controller methods
I will continue to use the previous controller method, as follows:
@RequestMapping("c1/param3")
public void objParam2(Student student){
System.out.println(student);
}3.3 Configure filters
SpringMVC provides a filter for dealing with Chinese garbled characters. Configuring the filter in web.xml can solve the problem of Chinese garbled characters: add the following configuration:
<!-- SpringMVC中提供的字符编码过滤器，放在所有过滤器的最上方 -->
<filter>
<filter-name>encFilter</filter-name>
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>utf-8</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>encFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>3.4 Test results
Submit the above information to see if there are any garbled characters printed on the console. If there are no garbled characters, it means that the character encoding filter is configured successfully.
OK, it shows that it is indeed possible, and if the name attribute submitted in the form corresponds to the Student attribute, it can also be directly assigned to the corresponding parameter.
Related readings of previous columns & articles
If you don’t know anything about the content of this issue, you can also go to see the content of previous issues. The following is a series of column articles such as Maven and Mybatis carefully crafted by bloggers in the past. Don’t miss it when you pass by! If it is helpful to you, please like it and bookmark it. Among them, some of the Spring columns are being updated, so they cannot be viewed, but they can be viewed after the bloggers have completed all the updates.
1. Maven series of columns
| Maven Series Column | Maven project development |
| Maven aggregation development [example detailed explanation --- 5555 words] |