四十九、SpingBoot引入第三方filter

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最近手头活不多，被其他项目拉去帮忙。他们的需求是，项目中需要加入第三方的过滤器（用于单点登录认证的），项目采用的是spring boot，spring boot之前没深入玩过，所以费了些时间。

需求：

    第三方提供了一个filter以及使用标准web.xml时的配置方法，要求整合到项目中

过程：

    第一步：

    作为不百度（google）不会写代码的程序员，第一反应是去baidu一下，毕竟spring boot的使用停留在写web api的码砖水平上。百度结果，大部分都是用类似下面的方法：

    @Beanpublic FilterRegistrationBean pluginFilter(){//将第三方filter实例，配置信息设置到一个FilterRegistrationBean中//详细代码省略，网上到处都是}

    优点在于：简单。

    缺点：这种第三方的filter，如果是多个的，每个都得重新加这种方法，对于扩展来说，啰嗦

 

    于是，寻求spring boot项目直接使用web.xml里过滤器配置的方案，百度了好些，都是直接将spring boot项目变为使用web.xml配置的，这个动作有点大，怕把项目给搞乱了，没敢采用。。。

 

     第二步：

     目标明确为，使用Bean标签返回FilterRegistrationBean（或类似的接口实例）的方向，但是这个Bean要能将多个过滤器注册给spring。稍微读了一下源码，发现FilterRegistrationBean这个鬼，这正起作用的是定义在AbstractFilterRegistrationBean中的方法onStartup方法

public void onStartup(ServletContext servletContext) throws ServletException {Filter filter = this.getFilter();Assert.notNull(filter, "Filter must not be null");String name = this.getOrDeduceName(filter);if (!this.isEnabled()) {this.logger.info("Filter " + name + " was not registered (disabled)");} else { Dynamic added = servletContext.addFilter(name, filter);if (added == null) {this.logger.info("Filter " + name + " was not registered (possibly already registered?)");} else {this.configure(added);}}
}

    所以，咱们重写一下这个onStartup方法(类名后缀用的proxy可能不太合适，请不要在意细节)：

package com.xxx.common.filter;import org.dom4j.Document;
import org.dom4j.Element;
import org.springframework.boot.web.servlet.FilterRegistrationBean;import javax.servlet.Filter;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;public class XxxFilterRegistrationBeanProxy extends FilterRegistrationBean{private Document plugin_xml = null;//所有需要注册的filterprivate Map<String,FilterRegistrationBean> filterRegistrationBeans;public IdssFilterRegistrationBeanProxy() {}public Document getPlugin_xml() {return plugin_xml;}public void setPlugin_xml(Document plugin_xml) {this.plugin_xml = plugin_xml;}public IdssFilterRegistrationBeanProxy(Document plugin_xml) throws IllegalAccessException, InstantiationException, ClassNotFoundException {super();this.plugin_xml = plugin_xml;setFilterRegistrationBeans();}@Overridepublic void onStartup(ServletContext servletContext) throws ServletException {if(filterRegistrationBeans == null || filterRegistrationBeans.size()==0) return;//执行实际的FilterRegistrationBean的onStartup方法for(FilterRegistrationBean bean : filterRegistrationBeans.values()){bean.onStartup(servletContext);}}private void setFilterRegistrationBeans() throws ClassNotFoundException, IllegalAccessException, InstantiationException {//读取xml配置文件，实例化FilterRegistrationBeanif(plugin_xml == null) return;filterRegistrationBeans = new HashMap<>();Element root = plugin_xml.getRootElement();Iterator<Element> filter_roots = root.elementIterator("filter");int order = 0;while (filter_roots.hasNext()){order++;Element filter_root = filter_roots.next();String filter_name = filter_root.elementText("filter-name").trim();String class_name = filter_root.elementText("filter-class").trim();Filter filter = (Filter) Class.forName(class_name).newInstance();FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();filterRegistrationBean.setFilter(filter);filterRegistrationBean.setName(filter_name);filterRegistrationBean.setOrder(order);Iterator<Element> parm_settings = filter_root.elementIterator("init-param");while (parm_settings.hasNext()){Element parm = parm_settings.next();filterRegistrationBean.addInitParameter(parm.elementText("param-name").trim(),parm.elementText("param-value").trim());}filterRegistrationBeans.put(filter_name,filterRegistrationBean);}Iterator<Element> filter_mappings = root.elementIterator("filter-mapping");while (filter_mappings.hasNext()){Element filter_mapping = filter_mappings.next();String filter_name = filter_mapping.elementText("filter-name");if(filterRegistrationBeans.containsKey(filter_name)){filterRegistrationBeans.get(filter_name).addUrlPatterns(filter_mapping.elementText("url-pattern"));}}}
}

注入spring boot的单例类中，给出一个Bean注解的方法，返回上面类的实例

package com.xxx.common.filter;import com.xxx.common.utils.PropertyUtil;
import org.dom4j.Document;
import org.dom4j.DocumentException;
import org.dom4j.io.SAXReader;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;import javax.annotation.PostConstruct;
import java.io.IOException;
import java.io.InputStreamReader;@Component
public class XxxPluginFilter {private XxxFilterRegistrationBeanProxy XxxFilterRegistrationBeanProxy = new XxxFilterRegistrationBeanProxy();private Document plugin_xml = null;private final static String plugin_filter_path = PropertyUtil.getProperty("plugin_filter_path");@Beanpublic FilterRegistrationBean pluginFilter(){return XxxFilterRegistrationBeanProxy;}@PostConstructprivate void init() throws IllegalAccessException, InstantiationException, ClassNotFoundException {if(plugin_filter_path == null || plugin_filter_path.isEmpty()) return;SAXReader reader = new SAXReader();InputStreamReader inputStreamReader = null;try {inputStreamReader = new InputStreamReader(this.getClass().getClassLoader().getResourceAsStream(plugin_filter_path));plugin_xml = reader.read(inputStreamReader);xxxFilterRegistrationBeanProxy = new XxxFilterRegistrationBeanProxy(plugin_xml);} catch (DocumentException e) {e.printStackTrace();} finally {if(inputStreamReader != null) {try {inputStreamReader.close();} catch (IOException e) {e.printStackTrace();}}}}
}

filter的xml配置文件示例：

<?xml version="1.0" encoding="UTF-8"?>
<plugin-filter><filter><filter-name>filter1</filter-name><filter-class>com.test.Filter1</filter-class><init-param><param-name>servername</param-name><param-value>http://localhost:8081</param-value></init-param></filter><filter><filter-name>filter2</filter-name><filter-class>com.test.Filter2</filter-class><init-param><param-name>initteset</param-name><param-value>yyyy</param-value></init-param></filter><filter-mapping><!-- 需要过滤的路径和文件类型 --><filter-name>filter1</filter-name><url-pattern>/*</url-pattern></filter-mapping><filter-mapping><filter-name>filter2</filter-name><url-pattern>/api/*</url-pattern></filter-mapping>
</plugin-filter>

简单粗暴而有效

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