SpringMVC学习中遇到编码问题（过滤器）

一、准备

1、创建一个简单的spring项目，具体不多说，这里主要使用Java配置来搭建。

2、这里我们就只简单的添加两个主要的包（若是想要其他的自己添加）

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webmvc</artifactId>
    <version>5.3.29</version>
</dependency>

<!-- 这里重点使用3.1+的版本，低版本的有几个方法没有（或是不一样，减少多余的麻烦） -->
<!-- v 3.1+ -->
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>4.0.1</version>
    <scope>provided</scope>
</dependency>

二、！！！重点来了

3、编写xml配置实现实现

创建一个文件：WebDispatcherInitializer.java(名称自编，最好规范，我的这个也只是满足我自己)
然后继承AbstractAnnotationConfigDispatcherServletInitializer，重写他的三个方法：

@Override
protected Class<?>[] getRootConfigClasses() {
    return new Class[]{RootConfig.class};
}

@Override
protected Class<?>[] getServletConfigClasses() {
    return new Class[]{WebServletConfig.class};
}

@Override
protected String[] getServletMappings() {
    return new String[]{"/"};
}

其中：RootConfig.java先照来,重点关注WebServletConfig.java：

@Configuration
@ComponentScan(value = "com.xxx",
        excludeFilters = {
                @ComponentScan.Filter(type = FilterType.ANNOTATION, value = EnableWebMvc.class)
        }
)
public class RootConfig {

}

在当前文件下再重写一个方法，主要是设置监听器，过滤器，servlet等

@Override
public void onStartup(ServletContext servletContext) throws ServletException {
    // 注册servlet
    // ServletRegistration.Dynamic myServlet = servletContext.addServlet("myServlet", MyServlet.class);
    // myServlet.addMapping("/custom/**");
    // myServlet.setLoadOnStartup(1);

    AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
    context.scan("com.xxx");
    servletContext.addListener(new ContextLoaderListener(context));
    ServletRegistration.Dynamic servlet = servletContext.addServlet("mvc", new DispatcherServlet(new GenericWebApplicationContext()));
    servlet.setLoadOnStartup(1);
    servlet.addMapping("/");
}

接下来就是WebServletConfig，他也需要继承一个类：WebMvcConfigurerAdapter，但是发现它被弃用了，当然你也可以继续，但是我这里就换成实现一个接口，其实这个类也是实现该接口

@Configuration
// 开启mvc
@EnableWebMvc
@ComponentScan(basePackages = {"com.xxx"})
public class WebServletConfig implements WebMvcConfigurer {
}

这里先配置一下视图解析

@Bean
public ViewResolver viewResolver() {
     InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
     viewResolver.setPrefix("/WEB-INF/views/");
     viewResolver.setSuffix(".jsp");
     // 存在这个会报错
     // viewResolver.setViewClass(JstlView.class);
     return viewResolver;
 }

此时自己先随便编写个视图：

@Controller
@RequestMapping("/custom")
public class MyController {

    @RequestMapping(value = "/demo", method = RequestMethod.GET)
    public String hello(Model model) {
        model.addAttribute("message", "Hello World, 你好，世界");
        return "home";
    }

    @ResponseBody
    // 当然出现乱码也可以在@RequestMapping加上, produces = "application/json;charset=UTF-8"，但是这样每个口都要写繁琐
    @RequestMapping(value = "/hello", method = RequestMethod.GET)
    public String hello() {
        return "我就只是一个简单的Hello，我再测试一下是否真的正常了";
    }
}

home.jsp

<%@ page contentType="text/html;charset=UTF-8" %>
<html>
<head>
    <title>Home</title>
</head>
<body>
<h1>${message}</h1>
</body>
</html>

项目目录如下：
在这里插入图片描述

在这里插入图片描述
启动项目，这里两个接口：
第一个：/demo
看着正常显示

接口信息也是UTF-8编码

第二个：/hello
明显看到中文编码全部变成了???

编码也不是标准编码

解决

1、先说第一个简单的在@RequestMapping上加上produces = “application/json;charset=UTF-8”
显示正常了，并且编码也是指定的那一个
在这里插入图片描述

但是这个得给每一个都加上，不方便，也不可能每一个都是该类型

2、第二种全局配置，继续回到WebServletConfig中，它有一个方法：configureMessageConverters重写它

@Override
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    StringHttpMessageConverter converter = new StringHttpMessageConverter();
    // 设置信息编码为UTF-8
    converter.setDefaultCharset(StandardCharsets.UTF_8);
    // 类型就设置为全类型，他自己根据情况来MediaType源码如下文，具体自己看源码
    converter.setSupportedMediaTypes(Collections.singletonList(MediaType.ALL));
    converters.add(converter);
}

再看结果：
看到也是正常的
在这里插入图片描述
而且Content-Type:也不是和之前指定一样，他这里是text/html

- - - END - - -

附：

public static final MediaType ALL;

	/**
	 * A String equivalent of {@link MediaType#ALL}.
	 */
	public static final String ALL_VALUE = "*/*";

	/**
	 *  Public constant media type for {@code application/atom+xml}.
	 */
	public static final MediaType APPLICATION_ATOM_XML;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_ATOM_XML}.
	 */
	public static final String APPLICATION_ATOM_XML_VALUE = "application/atom+xml";

	/**
	 * Public constant media type for {@code application/cbor}.
	 * @since 5.2
	 */
	public static final MediaType APPLICATION_CBOR;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_CBOR}.
	 * @since 5.2
	 */
	public static final String APPLICATION_CBOR_VALUE = "application/cbor";

	/**
	 * Public constant media type for {@code application/x-www-form-urlencoded}.
	 */
	public static final MediaType APPLICATION_FORM_URLENCODED;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_FORM_URLENCODED}.
	 */
	public static final String APPLICATION_FORM_URLENCODED_VALUE = "application/x-www-form-urlencoded";

	/**
	 * Public constant media type for {@code application/graphql+json}.
	 * @since 5.3.19
	 * @see <a href="https://github.com/graphql/graphql-over-http">GraphQL over HTTP spec</a>
	 */
	public static final MediaType APPLICATION_GRAPHQL;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_GRAPHQL}.
	 * @since 5.3.19
	 */
	public static final String APPLICATION_GRAPHQL_VALUE = "application/graphql+json";

	/**
	 * Public constant media type for {@code application/json}.
	 */
	public static final MediaType APPLICATION_JSON;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_JSON}.
	 * @see #APPLICATION_JSON_UTF8_VALUE
	 */
	public static final String APPLICATION_JSON_VALUE = "application/json";

	/**
	 * Public constant media type for {@code application/json;charset=UTF-8}.
	 * @deprecated as of 5.2 in favor of {@link #APPLICATION_JSON}
	 * since major browsers like Chrome
	 * <a href="https://bugs.chromium.org/p/chromium/issues/detail?id=438464">
	 * now comply with the specification</a> and interpret correctly UTF-8 special
	 * characters without requiring a {@code charset=UTF-8} parameter.
	 */
	@Deprecated
	public static final MediaType APPLICATION_JSON_UTF8;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_JSON_UTF8}.
	 * @deprecated as of 5.2 in favor of {@link #APPLICATION_JSON_VALUE}
	 * since major browsers like Chrome
	 * <a href="https://bugs.chromium.org/p/chromium/issues/detail?id=438464">
	 * now comply with the specification</a> and interpret correctly UTF-8 special
	 * characters without requiring a {@code charset=UTF-8} parameter.
	 */
	@Deprecated
	public static final String APPLICATION_JSON_UTF8_VALUE = "application/json;charset=UTF-8";

	/**
	 * Public constant media type for {@code application/octet-stream}.
	 */
	public static final MediaType APPLICATION_OCTET_STREAM;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_OCTET_STREAM}.
	 */
	public static final String APPLICATION_OCTET_STREAM_VALUE = "application/octet-stream";

	/**
	 * Public constant media type for {@code application/pdf}.
	 * @since 4.3
	 */
	public static final MediaType APPLICATION_PDF;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_PDF}.
	 * @since 4.3
	 */
	public static final String APPLICATION_PDF_VALUE = "application/pdf";

	/**
	 * Public constant media type for {@code application/problem+json}.
	 * @since 5.0
	 * @see <a href="https://tools.ietf.org/html/rfc7807#section-6.1">
	 *     Problem Details for HTTP APIs, 6.1. application/problem+json</a>
	 */
	public static final MediaType APPLICATION_PROBLEM_JSON;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_PROBLEM_JSON}.
	 * @since 5.0
	 */
	public static final String APPLICATION_PROBLEM_JSON_VALUE = "application/problem+json";

	/**
	 * Public constant media type for {@code application/problem+json}.
	 * @since 5.0
	 * @see <a href="https://tools.ietf.org/html/rfc7807#section-6.1">
	 *     Problem Details for HTTP APIs, 6.1. application/problem+json</a>
	 * @deprecated as of 5.2 in favor of {@link #APPLICATION_PROBLEM_JSON}
	 * since major browsers like Chrome
	 * <a href="https://bugs.chromium.org/p/chromium/issues/detail?id=438464">
	 * now comply with the specification</a> and interpret correctly UTF-8 special
	 * characters without requiring a {@code charset=UTF-8} parameter.
	 */
	@Deprecated
	public static final MediaType APPLICATION_PROBLEM_JSON_UTF8;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_PROBLEM_JSON_UTF8}.
	 * @since 5.0
	 * @deprecated as of 5.2 in favor of {@link #APPLICATION_PROBLEM_JSON_VALUE}
	 * since major browsers like Chrome
	 * <a href="https://bugs.chromium.org/p/chromium/issues/detail?id=438464">
	 * now comply with the specification</a> and interpret correctly UTF-8 special
	 * characters without requiring a {@code charset=UTF-8} parameter.
	 */
	@Deprecated
	public static final String APPLICATION_PROBLEM_JSON_UTF8_VALUE = "application/problem+json;charset=UTF-8";

	/**
	 * Public constant media type for {@code application/problem+xml}.
	 * @since 5.0
	 * @see <a href="https://tools.ietf.org/html/rfc7807#section-6.2">
	 *     Problem Details for HTTP APIs, 6.2. application/problem+xml</a>
	 */
	public static final MediaType APPLICATION_PROBLEM_XML;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_PROBLEM_XML}.
	 * @since 5.0
	 */
	public static final String APPLICATION_PROBLEM_XML_VALUE = "application/problem+xml";

	/**
	 * Public constant media type for {@code application/rss+xml}.
	 * @since 4.3.6
	 */
	public static final MediaType APPLICATION_RSS_XML;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_RSS_XML}.
	 * @since 4.3.6
	 */
	public static final String APPLICATION_RSS_XML_VALUE = "application/rss+xml";

	/**
	 * Public constant media type for {@code application/x-ndjson}.
	 * @since 5.3
	 */
	public static final MediaType APPLICATION_NDJSON;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_NDJSON}.
	 * @since 5.3
	 */
	public static final String APPLICATION_NDJSON_VALUE = "application/x-ndjson";

	/**
	 * Public constant media type for {@code application/stream+json}.
	 * @since 5.0
	 * @deprecated as of 5.3, see notice on {@link #APPLICATION_STREAM_JSON_VALUE}.
	 */
	@Deprecated
	public static final MediaType APPLICATION_STREAM_JSON;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_STREAM_JSON}.
	 * @since 5.0
	 * @deprecated as of 5.3 since it originates from the W3C Activity Streams
	 * specification which has a more specific purpose and has been since
	 * replaced with a different mime type. Use {@link #APPLICATION_NDJSON} as
	 * a replacement or any other line-delimited JSON format (e.g. JSON Lines,
	 * JSON Text Sequences).
	 */
	@Deprecated
	public static final String APPLICATION_STREAM_JSON_VALUE = "application/stream+json";

	/**
	 * Public constant media type for {@code application/xhtml+xml}.
	 */
	public static final MediaType APPLICATION_XHTML_XML;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_XHTML_XML}.
	 */
	public static final String APPLICATION_XHTML_XML_VALUE = "application/xhtml+xml";

	/**
	 * Public constant media type for {@code application/xml}.
	 */
	public static final MediaType APPLICATION_XML;

	/**
	 * A String equivalent of {@link MediaType#APPLICATION_XML}.
	 */
	public static final String APPLICATION_XML_VALUE = "application/xml";

	/**
	 * Public constant media type for {@code image/gif}.
	 */
	public static final MediaType IMAGE_GIF;

	/**
	 * A String equivalent of {@link MediaType#IMAGE_GIF}.
	 */
	public static final String IMAGE_GIF_VALUE = "image/gif";

	/**
	 * Public constant media type for {@code image/jpeg}.
	 */
	public static final MediaType IMAGE_JPEG;

	/**
	 * A String equivalent of {@link MediaType#IMAGE_JPEG}.
	 */
	public static final String IMAGE_JPEG_VALUE = "image/jpeg";

	/**
	 * Public constant media type for {@code image/png}.
	 */
	public static final MediaType IMAGE_PNG;

	/**
	 * A String equivalent of {@link MediaType#IMAGE_PNG}.
	 */
	public static final String IMAGE_PNG_VALUE = "image/png";

	/**
	 * Public constant media type for {@code multipart/form-data}.
	 */
	public static final MediaType MULTIPART_FORM_DATA;

	/**
	 * A String equivalent of {@link MediaType#MULTIPART_FORM_DATA}.
	 */
	public static final String MULTIPART_FORM_DATA_VALUE = "multipart/form-data";

	/**
	 * Public constant media type for {@code multipart/mixed}.
	 * @since 5.2
	 */
	public static final MediaType MULTIPART_MIXED;

	/**
	 * A String equivalent of {@link MediaType#MULTIPART_MIXED}.
	 * @since 5.2
	 */
	public static final String MULTIPART_MIXED_VALUE = "multipart/mixed";

	/**
	 * Public constant media type for {@code multipart/related}.
	 * @since 5.2.5
	 */
	public static final MediaType MULTIPART_RELATED;

	/**
	 * A String equivalent of {@link MediaType#MULTIPART_RELATED}.
	 * @since 5.2.5
	 */
	public static final String MULTIPART_RELATED_VALUE = "multipart/related";

	/**
	 * Public constant media type for {@code text/event-stream}.
	 * @since 4.3.6
	 * @see <a href="https://www.w3.org/TR/eventsource/">Server-Sent Events W3C recommendation</a>
	 */
	public static final MediaType TEXT_EVENT_STREAM;

	/**
	 * A String equivalent of {@link MediaType#TEXT_EVENT_STREAM}.
	 * @since 4.3.6
	 */
	public static final String TEXT_EVENT_STREAM_VALUE = "text/event-stream";

	/**
	 * Public constant media type for {@code text/html}.
	 */
	public static final MediaType TEXT_HTML;

	/**
	 * A String equivalent of {@link MediaType#TEXT_HTML}.
	 */
	public static final String TEXT_HTML_VALUE = "text/html";

	/**
	 * Public constant media type for {@code text/markdown}.
	 * @since 4.3
	 */
	public static final MediaType TEXT_MARKDOWN;

	/**
	 * A String equivalent of {@link MediaType#TEXT_MARKDOWN}.
	 * @since 4.3
	 */
	public static final String TEXT_MARKDOWN_VALUE = "text/markdown";

	/**
	 * Public constant media type for {@code text/plain}.
	 */
	public static final MediaType TEXT_PLAIN;

	/**
	 * A String equivalent of {@link MediaType#TEXT_PLAIN}.
	 */
	public static final String TEXT_PLAIN_VALUE = "text/plain";

	/**
	 * Public constant media type for {@code text/xml}.
	 */
	public static final MediaType TEXT_XML;

	/**
	 * A String equivalent of {@link MediaType#TEXT_XML}.
	 */
	public static final String TEXT_XML_VALUE = "text/xml";

	private static final String PARAM_QUALITY_FACTOR = "q";


	static {
		// Not using "valueOf' to avoid static init cost
		ALL = new MediaType("*", "*");
		APPLICATION_ATOM_XML = new MediaType("application", "atom+xml");
		APPLICATION_CBOR = new MediaType("application", "cbor");
		APPLICATION_FORM_URLENCODED = new MediaType("application", "x-www-form-urlencoded");
		APPLICATION_GRAPHQL = new MediaType("application", "graphql+json");
		APPLICATION_JSON = new MediaType("application", "json");
		APPLICATION_JSON_UTF8 = new MediaType("application", "json", StandardCharsets.UTF_8);
		APPLICATION_NDJSON = new MediaType("application", "x-ndjson");
		APPLICATION_OCTET_STREAM = new MediaType("application", "octet-stream");
		APPLICATION_PDF = new MediaType("application", "pdf");
		APPLICATION_PROBLEM_JSON = new MediaType("application", "problem+json");
		APPLICATION_PROBLEM_JSON_UTF8 = new MediaType("application", "problem+json", StandardCharsets.UTF_8);
		APPLICATION_PROBLEM_XML = new MediaType("application", "problem+xml");
		APPLICATION_RSS_XML = new MediaType("application", "rss+xml");
		APPLICATION_STREAM_JSON = new MediaType("application", "stream+json");
		APPLICATION_XHTML_XML = new MediaType("application", "xhtml+xml");
		APPLICATION_XML = new MediaType("application", "xml");
		IMAGE_GIF = new MediaType("image", "gif");
		IMAGE_JPEG = new MediaType("image", "jpeg");
		IMAGE_PNG = new MediaType("image", "png");
		MULTIPART_FORM_DATA = new MediaType("multipart", "form-data");
		MULTIPART_MIXED = new MediaType("multipart", "mixed");
		MULTIPART_RELATED = new MediaType("multipart", "related");
		TEXT_EVENT_STREAM = new MediaType("text", "event-stream");
		TEXT_HTML = new MediaType("text", "html");
		TEXT_MARKDOWN = new MediaType("text", "markdown");
		TEXT_PLAIN = new MediaType("text", "plain");
		TEXT_XML = new MediaType("text", "xml");
	}