四十九、SpingBoot引入第三方filter
阿新 • • 發佈：2018-12-28
最近手頭活不多，被其他專案拉去幫忙。他們的需求是，專案中需要加入第三方的過濾器（用於單點登入認證的），專案採用的是spring boot，spring boot之前沒深入玩過，所以費了些時間。
需求：
第三方提供了一個filter以及使用標準web.xml時的配置方法，要求整合到專案中
過程：
第一步：
作為不百度（google）不會寫程式碼的程式設計師，第一反應是去baidu一下，畢竟spring boot的使用停留在寫web api的碼磚水平上。百度結果，大部分都是用類似下面的方法：
@Bean public FilterRegistrationBean pluginFilter(){ //將第三方filter例項，配置資訊設定到一個FilterRegistrationBean中 //詳細程式碼省略，網上到處都是 }
優點在於：簡單。
缺點：這種第三方的filter，如果是多個的，每個都得重新加這種方法，對於擴充套件來說，囉嗦
於是，尋求spring boot專案直接使用web.xml裡過濾器配置的方案，百度了好些，都是直接將spring boot專案變為使用web.xml配置的，這個動作有點大，怕把專案給搞亂了，沒敢採用。。。
第二步：
目標明確為，使用Bean標籤返回FilterRegistrationBean（或類似的介面例項）的方向，但是這個Bean要能將多個過濾器註冊給spring。稍微讀了一下原始碼，發現FilterRegistrationBean這個鬼，這正起作用的是定義在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);
所以，咱們重寫一下這個onStartup方法(類名字尾用的proxy可能不太合適，請不要在意細節)：
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;
//所有需要註冊的filter
private 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();
}
@Override
public void onStartup(ServletContext servletContext) throws ServletException {
if(filterRegistrationBeans == null || filterRegistrationBeans.size()==0) return;
//執行實際的FilterRegistrationBean的onStartup方法
for(FilterRegistrationBean bean : filterRegistrationBeans.values()){
bean.onStartup(servletContext);
}
}
private void setFilterRegistrationBeans() throws ClassNotFoundException, IllegalAccessException, InstantiationException {
//讀取xml配置檔案，例項化FilterRegistrationBean
if(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的單例類中，給出一個Bean註解的方法，返回上面類的例項
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");
@Bean
public FilterRegistrationBean pluginFilter(){
return XxxFilterRegistrationBeanProxy;
}
@PostConstruct
private 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配置檔案示例：
<?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>
<!-- 需要過濾的路徑和檔案型別 -->
<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>
簡單粗暴而有效