spring boot 整合web开发之文件上传、静态资源访问、异常处理、返回JSON数据

• 目录

  

  springboot 整合web开发

  ---

• 返回json数据
• 静态资源访问
• 文件上传
• 全局异常

 1、返回json数据

springboot默认的是jackson-databind做为json处理器、也可以使用自定义转换器：gson、fastjson

gson集成方式为：在pom文件中排除jackson-databind jar包，添加gson包。

    org.springframework.boot
    spring-boot-starter-web
    
        
            com.fasterxml.jackson.core
            jackson-databind
        
    

dependency>
    com.google.code.gson
    gson

springboot默认提供了Gson自动转换类GsonHttpMessageConvertersConfiguration，因此Gson依赖添加成功后，可以像使用json-databind那样使用Gson。但是如果想格式化日期等操作得需要自己自定义。

@Configuration
public class GsonConfig {

    @Bean
    GsonHttpMessageConverter gsonHttpMessageConverter() {
        GsonHttpMessageConverter gsonHttpMessageConverter = new GsonHttpMessageConverter();
        GsonBuilder builder = new GsonBuilder();
        builder.setDateFormat("yyyy-MM-dd");
        builder.excludeFieldsWithModifiers(Modifier.PROTECTED);
        Gson gson = builder.create();
        gsonHttpMessageConverter.setGson(gson);
        return gsonHttpMessageConverter;
    }

}

fastJson集成方式：在pom文件中排除jackson-databind jar包，添加fastjson

    org.springframework.boot
    spring-boot-starter-web
    
        
            com.fasterxml.jackson.core
            jackson-databind
        
    


    com.alibaba
    fastjson
    1.2.56

配置fastjson的HttpMessageConverter

@Configuration
public class MyFastJsonConfig {

    @Bean
    FastJsonHttpMessageConverter fastJsonHttpMessageConverter() {
        FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
        FastJsonConfig config = new FastJsonConfig();
        config.setDateFormat("yyyy-MM-dd");
        config.setCharset(Charset.forName("UTF-8"));
        config.setSerializerFeatures(
                SerializerFeature.WriteClassName,
                SerializerFeature.WriteMapNullValue,
                SerializerFeature.PrettyFormat,
                SerializerFeature.WriteNullListAsEmpty,
                SerializerFeature.WriteNullStringAsEmpty
        );
        converter.setFastJsonConfig(config);
        return converter;
    }
}

 对于FastJsonHttpMessageConverter的配置，还有另一种方式。实现WevMvcConfigurer接口(spring5.0之前继承WebMvcConfigurerAdapter类来实现)

@Configuration
public class MyWebMvcConfig implements WebMvcConfigurer {

    //处理json
    @Override
    public void configureMessageConverters(List> converters) {
        FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
        FastJsonConfig config = new FastJsonConfig();
        config.setDateFormat("yyyy-MM-dd");
        config.setCharset(Charset.forName("UTF-8"));
        config.setSerializerFeatures(
                SerializerFeature.WriteClassName,
                SerializerFeature.WriteMapNullValue,
                SerializerFeature.PrettyFormat,
                SerializerFeature.WriteNullListAsEmpty,
                SerializerFeature.WriteNullStringAsEmpty
        );
        converter.setFastJsonConfig(config);
        converters.add(converter);
    }

    //自定义静态资源位置
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/static/**")
                .addResourceLocations("classpath:/static/");
    }
}

 2、静态资源访问

springboot默认会过滤所有的静态资源，默认静态资源5个位置(classpath:/META-INF/resources/、classpath:/resources/、classpath:/static/、classpath:/public/、/)，优先级依次降低。

自定义过滤策略：1）、可以在application.properties直接定义过滤规则

spring.mvc.static-path-pattern=/static/**

spring.resources.static-locations=classpath:/static

 2）、java编码实现

@Configuration
public class MyWebMvcConfig implements WebMvcConfigurer {

    //处理json
    @Override
    public void configureMessageConverters(List> converters) {
        FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
        FastJsonConfig config = new FastJsonConfig();
        config.setDateFormat("yyyy-MM-dd");
        config.setCharset(Charset.forName("UTF-8"));
        config.setSerializerFeatures(
                SerializerFeature.WriteClassName,
                SerializerFeature.WriteMapNullValue,
                SerializerFeature.PrettyFormat,
                SerializerFeature.WriteNullListAsEmpty,
                SerializerFeature.WriteNullStringAsEmpty
        );
        converter.setFastJsonConfig(config);
        converters.add(converter);
    }

    //自定义静态资源位置
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {
        registry.addResourceHandler("/static/**")
                .addResourceLocations("classpath:/static/");
    }
}

3、文件上传

文件上传一共涉及两个组件，一个是CommonsMultipartResolver基于commons-fileupload来处理，另一个是StandardServletMultipartResolver基于serlver3.0multipart 。springboot默认采用的是StandardServletMultipartResolver做为上传组件。

如果想使用CommonsMultipartResolver做为上传组件代码如下：

pom文件需要加入common jar包

 
            commons-io
            commons-io
            1.4
       

       
       
            commons-fileupload
            commons-fileupload
            1.3.1
       

@Configuration
public class MyCommonsMultipartResolver {

    @Bean
    public CommonsMultipartResolver commonsMultipartResolver() {
        CommonsMultipartResolver commonsMultipartResolver = new CommonsMultipartResolver();
        commonsMultipartResolver.setResolveLazily(true);//resolveLazily属性启用是为了推迟文件解析，以在在UploadAction中捕获文件大小异常
        commonsMultipartResolver.setMaxUploadSize(1024);
        commonsMultipartResolver.setDefaultEncoding("UTF-8");
        return commonsMultipartResolver;
    }
}

 4、全局异常处理

关键字@ControllerAdvice

1）、返回resonse代码如下，上传文件大小超过限制就会输出到页面。

@ControllerAdvice
public class CustomerExceptionHandler {

    @ExceptionHandler(MaxUploadSizeExceededException.class)
    public void uploadException(MaxUploadSizeExceededException e, HttpServletResponse resp) throws IOException {
        resp.setContentType("text/html;charset=utf-8");
        PrintWriter out = resp.getWriter();
        out.write("上传文件大小超限");
        out.flush();
        out.close();
    }
}

2）、返回ModelAndView

@ControllerAdvice
public class CustomerExceptionHtmlHandler {

    @ExceptionHandler(MaxUploadSizeExceededException.class)
    public ModelAndView uploadException(MaxUploadSizeExceededException e) throws IOException {
       ModelAndView view = new ModelAndView();
       view.addObject("msg","上传文件超限");
       view.setViewName("/error");
       return view;
    }
}

@ControllerAdvice还可以配置全局参数，具体代码如下

@ControllerAdvice
public class GlobalConfig {

    @ModelAttribute(value = "info")
    public Map userInfo() {
        Map map = new HashMap<>();
        map.put("usename","路遥");
        map.put("gender","男");
        return map;
    }
}

@RestController
public class GlobalController {

    @GetMapping("/global")
    public void globalParma(Model model) {
        Map map = model.asMap();
        Set strings =  map.keySet();
        Iterator iterator = strings.iterator();
        while (iterator.hasNext()) {
            String next = iterator.next();
            Object o = map.get(next);
            System.out.println(next + ">>>>>>" + o);
        }
    }
}

 

以上所有代码都在：https://github.com/FadeHub/spring-boot-learn 下面的spring-boot-web工程下