spring boot扫描自定义的servlet和filter

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。