拦截器与过滤器的区别以及如何自定义一个过滤器和拦截器

拦截器与过滤器的区别 ：

     1. 拦截器是基于java的反射机制的，而过滤器是基于函数回调。

     2. 拦截器不依赖与servlet容器，过滤器依赖与servlet容器。

     3. 拦截器只能对action请求起作用，而过滤器则可以对几乎所有的请求起作用。

     4. 拦截器可以访问action上下文、值栈里的对象，而过滤器不能访问。
     5. 在action的生命周期中，拦截器可以多次被调用，而过滤器只能在容器初始化时被调用一次.

自定义一个拦截器(SpringMVC):

Spring MVC也可以使用拦截器对请求进行拦截处理，用户可以自定义拦截器来实现特定的功能，自定义的拦截器必须实现HandlerInterceptor接口。

代码如下:

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.Iterator;
import java.util.Map;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;

public class UrlDecodeFilterInterceptor extends AbstractInterceptor {
private static final long serialVersionUID = -2335290125344040914L;
private static final Log LOG = LogFactory.getLog(UrlDecodeFilterInterceptor.class);

public String intercept(ActionInv
c982
ocation invocation) throws Exception {
Map parameters = invocation.getInvocationContext().getParameters();
HttpServletRequest request = ServletActionContext. getRequest();

if("get".equalsIgnoreCase(request.getMethod())){
for (Iterator i = parameters.keySet().iterator(); i.hasNext();) {
String param = (String) i.next();
String[] values = (String[])parameters.get(param);
if(values != null && values.length > 0){
for (int j = 0; j < values.length; j++) {
if(values[j] != null && !"".equals(values[j])){
try {
values[j] = new String(values[j].getBytes("iso8859-1"),"UTF-8");
parameters.put(param, values[j]);
} catch (UnsupportedEncodingException e1) {
e1.printStackTrace();
}
}
}
}
}
}

if("application/x-www-form-urlencoded;charset=UTF-8".equals(request.getContentType())){
for (Iterator i = parameters.keySet().iterator(); i.hasNext();) {
String param = (String) i.next();
String[] values = (String[])parameters.get(param);
if(values != null && values.length > 0){
for (int j = 0; j < values.length; j++) {
if(values[j] != null && !"".equals(values[j])){
try {
values[j] = URLDecoder.decode(values[j], "UTF-8");
parameters.put(param, values[j]);
} catch (UnsupportedEncodingException e1) {
e1.printStackTrace();
}
}
}
}
}
}

return invocation.invoke();
}
}
配置文件如
<interceptors>
<interceptor name="urlDecodeFilterInterceptor"
class="com.whaty.platform.sso.web.interceptor.UrlDecodeFilterInterceptor">
</interceptor>

<interceptor-stack name="urlDecodeStack">
<interceptor-ref name="urlDecodeFilterInterceptor"></interceptor-ref>
<interceptor-ref name="defaultStack"></interceptor-ref>
</interceptor-stack>

</interceptors>

当然,处理编码集可以通过springmvc自带的过滤器进行拦截,只需要在web.xml中配置即

<filter>
<filter-name>encodingFilter</filter-name>
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>UTF-8</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>encodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

自定义一个过滤器:

定义一个类去实现Filter.

代码实现

public class JspExportFilter implements Filter {
@Override
public void destroy() {

}

@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
//判断导出格式
String type= request.getParameter("t");

//文件名称（解码）
String exportName = URLDecoder.decode(request.getParameter("n"),"UTF-8");

//编码
exportName = URLEncoder.encode(exportName, "UTF-8");

if(exportName == null || exportName.isEmpty()){
exportName = "export";
}

if(type==null){
//null
chain.doFilter(request, response);
return;
}
//使用我们自定义的响应包装器来包装原始的ServletResponse
ResponseWrapper wrapper = new ResponseWrapper((HttpServletResponse)response);
//这句话非常重要，注意看到第二个参数是我们的包装器而不是response
chain.doFilter(request, wrapper);
String result = wrapper.getResult();
HttpServletResponse httpResp = (HttpServletResponse) response;
httpResp.reset();
response.setCharacterEncoding("UTF-8");
httpResp.setContentType("application/download");

ServletOutputStream sos = response.getOutputStream();
try{
if("xls".equals(type)){
//xls
String place="<html xmlns:v=\"urn:schemas-microsoft-com:vml\" "
+ "xmlns:o=\"urn:schemas-microsoft-com:office:office\" "
+ "xmlns:w=\"urn:schemas-microsoft-com:office:excel\" "
+ "xmlns:m=\"http://schemas.microsoft.com/office/2004/12/omml\" "
+ "xmlns=\"http://www.w3.org/TR/REC-html40\">";
result = result.replace("<html>", place);
httpResp.addHeader("Content-Disposition", "attachment;filename="+exportName+".xls");
sos.write(result.getBytes("UTF-8"));
}else if("doc".equals(type)){
//doc
String place="<html xmlns:v=\"urn:schemas-microsoft-com:vml\" "
+ "xmlns:o=\"urn:schemas-microsoft-com:office:office\" "
+ "xmlns:w=\"urn:schemas-microsoft-com:office:word\" "
+ "xmlns:m=\"http://schemas.microsoft.com/office/2004/12/omml\" "
+ "xmlns=\"http://www.w3.org/TR/REC-html40\">";
result = result.replace("<html>", place);
httpResp.addHeader("Content-Disposition", "attachment;filename="+exportName+".doc");
sos.write(result.getBytes("UTF-8"));
}else if("pdf".equals(type)){
//pdf
httpResp.addHeader("Content-Disposition", "attachment;filename="+exportName+".pdf");
try {
this.htmlCodeComeString(result, response.getOutputStream());
} catch (Exception e) {
BeanLog.getLogger().fatal("pdf export", e);
throw new IOException("pdf export", e);
}
}
}finally{
sos.close();
response.flushBuffer();
}
}

@Override
public void init(FilterConfig filterConfig) throws ServletException {

}

private void htmlCodeComeString(String htmlCode, OutputStream outstream) throws Exception {
Document doc = new Document(PageSize.A4.rotate());
try {
PdfWriter writer =PdfWriter.getInstance(doc, outstream);
ByteArrayInputStream bis = new ByteArrayInputStream(htmlCode.getBytes("UTF-8"));
// 解决中文问题：需要在导出jsp的样式中设置font-family: SimSun。例如：
/*
body{
font-size:12.0px; font-family: SimSun;
}
*/
//jsp必须是xhtml，而且头必须引入
//<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
doc.open();
XMLWorkerHelper.getInstance().parseXHtml(writer,
doc, bis, Charset.forName("UTF-8"));
doc.close();
bis.close();
}catch(Exception e) {
BeanLog.getLogger().fatal("pdf export", e);
throw e;
}
}

            在web.xml中配置
<filter>
<filter-name>jspExport</filter-name>
<filter-class>com.jbns.easymaster.web.sysmgr.filter.JspExportFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>jspExport</filter-name>
<url-pattern>/export/*</url-pattern>
</filter-mapping>