数据转换器是指将客户端 HTTP 请求中的参数转换为业务方法中定义的形参,自定义表示开发者可以自主设计转换的方式,HandlerApdter 已经提供了通用的转换,String 转 int,String 转 double,表单数据的封装等,但是在特殊的业务场景下,HandlerAdapter 无法进行转换,就需要开发者自定义转换器。
String 转 Date
客户端输入 String 类型的数据 “2019-03-03”,自定义转换器将该数据转为 Date 类型的对象。
- 创建 DateConverter 转换器,实现 Conveter 接口。
import org.springframework.core.convert.converter.Converter;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class DateConverter implements Converter<String, Date> {
private String pattern; //yyyy-mm-ss
public DateConverter(String pattern){
this.pattern = pattern;
}
@Override
public Date convert(String s) {
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(this.pattern);
Date date = null;
try {
date = simpleDateFormat.parse(s);
} catch (ParseException e) {
e.printStackTrace();
}
return date;
}
}
- springmvc.xml 配置转换器。
<!-- 配置自定义转换器 -->
<bean id="myComversion" class="org.springframework.context.support.ConversionServiceFactoryBean">
<property name="converters">
<list>
<bean class="com.southwind.converter.DateConverter">
<constructor-arg type="java.lang.String" value="yyyy-MM-dd"></constructor-arg>
</bean>
</list>
</property>
</bean>
<mvc:annotation-driven conversion-service="myComversion">
<!-- 消息转换器 -->
<mvc:message-converters register-defaults="true">
<bean class="org.springframework.http.converter.StringHttpMessageConverter">
<property name="supportedMediaTypes" value="text/html;charset=UTF-8"></property>
</bean>
<!-- 配置fastjson -->
<bean class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter4"></bean>
</mvc:message-converters>
</mvc:annotation-driven>
- JSP
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<form action="/converter/date" method="post">
请输入日期:<input type="text" name="date"/>(yyyy-MM-dd)<br/>
<input type="submit" value="提交"/>
</form>
</body>
</html>
- Handler
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.Date;
@RestController
@RequestMapping("/converter")
public class ConverterHandler {
@RequestMapping("/date")
public String date(Date date){
return date.toString();
}
}
String 转 Student
Student long id; String name; int age
StudentConverter.java
import com.southwind.entity.Student;
import org.springframework.core.convert.converter.Converter;
public class StudentConverter implements Converter<String, Student> {
@Override
public Student convert(String s) {
String[] args = s.split("-");
Student student = new Student();
student.setId(Long.parseLong(args[0]));
student.setName(args[1]);
student.setAge(Integer.parseInt(args[2]));
return student;
}
}
springmvc.xml
<!-- 配置自定义转换器 -->
<bean id="myConversion2" class="org.springframework.context.support.ConversionServiceFactoryBean">
<property name="converters">
<list>
<bean class="com.southwind.converter.DateConverter">
<constructor-arg type="java.lang.String" value="yyyy-MM-dd"></constructor-arg>
</bean>
<bean class="com.southwind.converter.StudentConverter"></bean>
</list>
</property>
</bean>
<mvc:annotation-driven conversion-service="myConversion2">
<!-- 消息转换器 -->
<mvc:message-converters register-defaults="true">
<bean class="org.springframework.http.converter.StringHttpMessageConverter">
<property name="supportedMediaTypes" value="text/html;charset=UTF-8"></property>
</bean>
<!-- 配置fastjson -->
<bean class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter4"></bean>
</mvc:message-converters>
</mvc:annotation-driven>
JSP
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<form action="/converter/student" method="post">
请输入学生信息:<input type="text" name="student"/>(id-name-age)<br/>
<input type="submit" value="提交"/>
</form>
</body>
</html>
Handler
@RequestMapping("/student")
public String student(Student student){
return student.toString();
}