SpringMVC03-HttpMessageConverter(自定义消息转换器)

Bertha 。 2021-09-23 13:14 378阅读 0赞

### 一、介绍 ###

> HttpMessageConverter是用来处理request（请求）和response（响应）里的数据。

### 二、需求 ###

> 自定义一个消息转换器，并注册这个HttpMessageConverter到SpringMVC中。

### 三、实现 ###

#### 1.新建DemoObj实体类 ####

package com.eleven.domain;
    
    public class DemoObj { 
    	private Long id;
    	private String name;
    	
    	public DemoObj() { 
    		super();
    	}
    	public DemoObj(Long id, String name) { 
    		super();
    		this.id = id;
    		this.name = name;
    	}
    	public Long getId() { 
    		return id;
    	}
    	public void setId(Long id) { 
    		this.id = id;
    	}
    	public String getName() { 
    		return name;
    	}
    	public void setName(String name) { 
    		this.name = name;
    	}
    
    }

#### 2.自定义HttpMessageConverter ####

package com.eleven.messageconverter;
    
    import java.io.IOException;
    import java.nio.charset.Charset;
    
    import org.springframework.http.HttpInputMessage;
    import org.springframework.http.HttpOutputMessage;
    import org.springframework.http.MediaType;
    import org.springframework.http.converter.AbstractHttpMessageConverter;
    import org.springframework.http.converter.HttpMessageNotReadableException;
    import org.springframework.http.converter.HttpMessageNotWritableException;
    import org.springframework.util.StreamUtils;
    
    import com.eleven.domain.DemoObj;
    
    public class MyMessageConverter extends AbstractHttpMessageConverter<DemoObj> {  // 继承AbstractHttpMessageConverter接口实现自定义的HttpMessageConverterF
    	public MyMessageConverter() { 
    		super(new MediaType("application", "x-eleven", Charset.forName("UTF-8")));// 自定义新建一个媒体类型application/x-eleven
    	}
    
    	/** * 重写readInternal里面的方法，处理请求的数据。 * 用"-"隔开表示的数据，转换成DemoObj的对象。 */
    	@Override
    	protected DemoObj readInternal(Class<? extends DemoObj> clazz, HttpInputMessage inputMessage)
    			throws IOException, HttpMessageNotReadableException { 
    		String temp = StreamUtils.copyToString(inputMessage.getBody(),
    
    				Charset.forName("UTF-8"));
    		String[] tempArr = temp.split("-");
    		return new DemoObj(new Long(tempArr[0]), tempArr[1]);
    	}
    
    	/** * 声明这个HttpMessageConverter只处理DemoObj这个类 */
    	@Override
    	protected boolean supports(Class<?> clazz) { 
    		return DemoObj.class.isAssignableFrom(clazz);
    	}
    
    	/** * 重写writeInternal方法，处理如何输出数据到response中。 * 并在前面原样输出hello */
    	@Override
    	protected void writeInternal(DemoObj obj, HttpOutputMessage outputMessage)
    			throws IOException, HttpMessageNotWritableException { 
    		String out = "hello:" + obj.getId() + "-" + obj.getName();
    		outputMessage.getBody().write(out.getBytes());
    	}
    
    }

#### 3.添加addviewController添加映射访问地址 ####

package com.eleven;
    
    import java.util.List;
    
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.ComponentScan;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.http.converter.HttpMessageConverter;
    import org.springframework.web.servlet.config.annotation.EnableWebMvc;
    import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
    import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
    import org.springframework.web.servlet.view.InternalResourceViewResolver;
    import org.springframework.web.servlet.view.JstlView;
    
    import com.eleven.messageconverter.MyMessageConverter;
    
    @Configuration // 声明当前类是一个配置类
    @EnableWebMvc // 开启SpringMVC的注解
    @ComponentScan("com.eleven") // 自动扫描包下面的注解和配置
    public class MyMvcConfig extends WebMvcConfigurerAdapter { 
    
    	/** * 01-此处配置了JSP的，用来映射路径和实际页面的位置 * * @return */
    	@Bean
    	public InternalResourceViewResolver viewResolver() { 
    		InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
    		viewResolver.setPrefix("/WEB-INF/classes/views/");
    		viewResolver.setSuffix(".jsp");
    		viewResolver.setViewClass(JstlView.class);
    		return viewResolver;
    	}
    
    	@Override
    	public void addViewControllers(ViewControllerRegistry registry) { 
    		registry.addViewController("/index").setViewName("/index");	// 访问index页面
    		registry.addViewController("/toUpload").setViewName("/upload");	// 文件上传
    		registry.addViewController("/converter").setViewName("converter");	// 自定义消息转换器
    
    	}
    	
    	/** * 仅添加一个自定义的HttpMessageConverter，不会覆盖默认注册的HttpMessageConverter */
    	@Override
    	public void extendMessageConverters(List<HttpMessageConverter<?>> converters) { 
            converters.add(converter());
        }
    	
    	@Bean 
    	public MyMessageConverter converter(){ 
    		return new MyMessageConverter();
    	}
    }

#### 3.编写ConverterController控制器 ####

package com.eleven.controller;
    
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.ResponseBody;
    
    import com.eleven.domain.DemoObj;
    
    @Controller // 返回的是字符串，一般都是与html页面渲染
    public class ConverterController { 
    	// 指定返回的媒体类型使我们自定义的媒体类型application/x-eleven 
    	@RequestMapping(value = "/convert", produces = {  "application/x-eleven" }) // 1
    	public @ResponseBody DemoObj convert(@RequestBody DemoObj demoObj) { 
    
    		return demoObj;
    	}
    
    }

#### 4.新建converter.jsp页面 ####

<%@ page language="java" contentType="text/html; charset=UTF-8"
    	pageEncoding="UTF-8"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>HttpMessageConverter Demo</title>
    </head>
    <body>
    	<div id="resp"></div>
    	<input type="button" onclick="req();" value="请求" />
    	<script src="https://code.jquery.com/jquery-3.4.1.min.js"></script>
    	<script> function req() { $.ajax({ url : "convert", data : "1-eleven", // 后台处理时，会用"-"隔开 type : "POST", contentType : "application/x-eleven", // 自定义成application/x-eleven success : function(data) { $("#resp").html(data); } }); } </script>
    </body>
    </html>

#### 5.运行访问 ####

> 输入地址：http://localhost:8080/springmvc02/converter

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxMjkzODk2_size_16_color_FFFFFF_t_70]

#### 6.小插曲 ####

问题：  
Content type ‘application/x-www-form-urlencoded;charset=UTF-8’ not supported  
解决：  
参数contentType写成了contenType（此处诊真是4只眼都不够用了，奔走中。。。。）

问题：  
jquery路径找不到，直接引用官方路径  
解决：

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