spring boot扫描自定义的servlet和filter

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spring boot扫描自定义的servlet和filter

这几天使用spring boot编写公司一个应用,在编写了一个filter,用于指定编码的filter,如下:

    /** * Created by xiaxuan on 16/11/1. */
    @WebFilter(urlPatterns = "/*",filterName="CharacterEncodeFilter",
            initParams={
                    @WebInitParam(name="encoding",value="UTF-8"),
                    @WebInitParam(name = "forceEncoding", value = "true")
            })
    @Singleton
    public class CharacterEncodingFilter implements Filter {

        private String encoding = "UTF-8";
        private boolean forceEncoding = true;

        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
            this.encoding = filterConfig.getInitParameter("encoding");
            String force = filterConfig.getInitParameter("forceEncoding");
            this.forceEncoding = (force == null) || Boolean.valueOf(force);
        }

        @Override
        public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
            if (this.forceEncoding || request.getCharacterEncoding() == null) {
                request.setCharacterEncoding(this.encoding);
                response.setCharacterEncoding(this.encoding);
            }
            chain.doFilter(request, response);
        }

        @Override
        public void destroy() {

        }

        public void setEncoding(String encoding) {
            this.encoding = encoding;
        }

        public void setForceEncoding(boolean forceEncoding) {
            this.forceEncoding = forceEncoding;
        }

    }

但是在实际使用的时候,却是完全没有起作用,后来查看了一下springboot的官方文档,filter和servlet、listener之类的需要单独进行注册才能使用,但是spring boot里面提供了一个注解来替代,为
@ServletComponentScan,这个注解直接加在对应的Application启动类上即可,如下:

    @SpringBootApplication
    @ServletComponentScan
    @ComponentScan
    public class SpringBootWebApplication {

        public static void main(String[] args) {
            SpringApplication.run(SpringBootWebApplication.class, args);
        }
    }

这样编写完之后,如果对应的filter是在自己当前模块下的某个package中的时候是可以起作用的,但是如果本身项目中有多个模块的时候,如果filter在一个类似与core下的package中,这样注解加上去并没有多大用处,最后会发现这个filter仍然没有起作用。

我自己编写的应用有两个,最开始的做法是把filter从core包中拆出来,然后在两个模块中各自添加一个,但是这样未免有些代码冗余,并且实现方式并不优雅,然后我查看了下@ServletComponentScan的源码,里面确实是有更好的解决方法。

@ServletComponentScan的源码如下:


    /** * Enables scanning for Servlet components ({@link WebFilter filters}, {@link WebServlet * servlets}, and {@link WebListener listeners}). Scanning is only performed when using an * embedded Servlet container. * <p> * Typically, one of {@code value}, {@code basePackages}, or {@code basePackageClasses} * should be specified to control the packages to be scanned for components. In their * absence, scanning will be performed from the package of the class with the annotation. * * @author Andy Wilkinson * @since 1.3.0 * @see WebServlet * @see WebFilter * @see WebListener */
    @Target(ElementType.TYPE)
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    @Import(ServletComponentScanRegistrar.class)
    public @interface ServletComponentScan {

        /** * Alias for the {@link #basePackages()} attribute. Allows for more concise annotation * declarations e.g.: {@code @ServletComponentScan("org.my.pkg")} instead of * {@code @ServletComponentScan(basePackages="org.my.pkg")}. * @return the base packages to scan */
        @AliasFor("basePackages")
        String[] value() default {};

        /** * Base packages to scan for annotated servlet components. {@link #value()} is an * alias for (and mutually exclusive with) this attribute. * <p> * Use {@link #basePackageClasses()} for a type-safe alternative to String-based * package names. * @return the base packages to scan */
        @AliasFor("value")
        String[] basePackages() default {};

        /** * Type-safe alternative to {@link #basePackages()} for specifying the packages to * scan for annotated servlet components. The package of each class specified will be * scanned. * @return classes from the base packages to scan */
        Class<?>[] basePackageClasses() default {};

    }

这里有一个value()属性,上面的注解默认为basePackage,那么在扫描的时候就只扫描当前模块下面的包,其他不扫描,如果要连同其他模块一起扫描的话,给这个属性加上值即可,如下:

    @ServletComponentScan(value = "cn.com")

如上,自定义的filter和servlet就可以正常起作用。


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