spring-消息转换器

//domain

package com.crazy.goods.tools;
/**
 * 0755-351512
 * @author Administrator
 *
 */
public class Phone {
    private String qno;
    private String number;
    public String getQno() {
        return qno;
    }
    public void setQno(String qno) {
        this.qno = qno;
    }
    public String getNumber() {
        return number;
    }
    public void setNumber(String number) {
        this.number = number;
    }

}

//消息转换器  要实现一个抽象类AbstractHttpMessageConverter

package com.crazy.goods.tools;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.converter.AbstractHttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;

public class MyMessageConvertor extends AbstractHttpMessageConverter<Phone> {

    /**
     * 将请求头数据转换成Phone
     */

    @Override
    protected Phone readInternal(Class<? extends Phone> arg0,
            HttpInputMessage msg) throws IOException,
            HttpMessageNotReadableException {
        //参数必须使用post提交必须在body中
        InputStream is=msg.getBody();
        BufferedReader br=new BufferedReader(new InputStreamReader(is));
        String param=br.readLine();
        String phone=param.split("=")[1];
        Phone phoneObj=new Phone();
        phoneObj.setQno(phone.split("-")[0]);
        phoneObj.setNumber(phone.split("-")[1]);
        return phoneObj;
    }
    /**
     * 当前的转换器支持转换的类
     */
    @Override
    protected boolean supports(Class<?> arg0) {
        if(arg0==Phone.class){
            return true;
        }
        return false;
    }
    /**
     * 用于将返回的对象转换成字符串显示在网页
     */
    @Override
    protected void writeInternal(Phone phone, HttpOutputMessage arg1)
            throws IOException, HttpMessageNotWritableException {
        String p=phone.getQno()+"-"+phone.getNumber();
        arg1.getBody().write(p.getBytes("UTF-8"));
    }

}

//springmvc.xml 要配置bean：消息转换器，只有post提交方式才会被转换器拦截

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
            http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
        ">
    <!--springmvc只能扫描控制层  -->
    <context:component-scan base-package="com.crazy.goods">
        <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Service"/>
        <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Repository"/>
    </context:component-scan>

    <!--消息转换器 必须使用post提交   -->
    <mvc:annotation-driven>
        <mvc:message-converters>
            <bean class="com.crazy.goods.tools.MyMessageConvertor">
                <property name="supportedMediaTypes">
                    <list>
                        <value>text/html;charset=UTF-8</value>
                          <value>application/x-www-form-urlencoded</value>
                    </list>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>
</beans>

servlet测试

package com.crazy.goods.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

import com.crazy.goods.tools.Phone;

/**
* @author Administrator
* 创建时间：2017年7月1日下午3:11:27
*/
@Controller
public class ReservePageServelt {

// /**
// * forward:转发
// * redirect:重定向
// * @param req
// * @param resp
// * @return
// * @throws ServletException
// * @throws IOException
// */
// @RequestMapping(value="/add",method={RequestMethod.GET})
// public String doGet(HttpServletRequest req, HttpServletResponse resp/*,@PathVariable("testid") String testid*/) throws ServletException, IOException {
// req.getRequestDispatcher("/reversegood.jsp").forward(req, resp);
// return "/reversegood.jsp";
// resp.getWriter().print(testid);
// }

//消息转换器思路，

//原理就是将请求体或者请求头的数据转换为action方法的参数，同时将方法的返回值的内容转换为响应头
//当url路径访问过来时，看到使用了@RequestBody注解，这个注解标识这个类要被消息转换器处理，就会springmvcxml文件中读到消息转换器，然后进入supports方法
//判断这个类是否被指定的转换器支持，如果支持，就调用readInternal方法，进行切割，然后将值传递到对象中,处理完成为对象之后，就会调用writeInternal转换为响应头
@RequestMapping(value="/add")
@ResponseBody
public Phone messageConvertor( @RequestBody Phone phone,HttpServletResponse response) {
System.out.println(phone.getQno()+phone.getNumber());
return phone;

}

}

总结：消息转换器的原理就是，自定义将请求体的数据转换为形参（对象），然后将方法的返回值内容转换为响应头

步骤：

当url路径访问过来时，看到使用了@RequestBody注解，这个注解标识这个类要被消息转换器处理，就会springmvcxml文件中读到消息转换器，然后进入supports方法
判断这个类是否被指定的转换器支持，如果支持，就调用readInternal方法，进行切割，然后将值传递到对象中.

处理完成为对象之后，就会调用writeInternal转换为响应头