filter过滤器

filter过滤器是配置在web.xml中，下面是代码：

    <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>

这只是最基本的filter字符编码过滤，网络上还有加强版本的过滤器，那是编写好了的文件，直接用就可以了。

由于文件无法上传，这里直接将源代码发出来，有两个文件。

第一个文件名：MVC_filter.java，代码如下：

package mvc_filter;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import mvc_filter.MyRequest;

@WebFilter("/MVC_filter")
public class MVC_filter implements Filter {
    public MVC_filter() {
    }

	public void destroy() {
	}

	public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
		HttpServletResponse response = (HttpServletResponse) res;
		HttpServletRequest request = (HttpServletRequest) req;
		request.setCharacterEncoding("UTF-8");
		response.setContentType("text/html;charset=UTF-8");
		MyRequest myRequest = new MyRequest(request);
		chain.doFilter(myRequest, response);
	}

	public void init(FilterConfig fConfig) throws ServletException {
	}

}

第二个文件名：MyRequest.java，源代码如下：

package mvc_filter;

import java.io.UnsupportedEncodingException;
import java.util.Map;
import java.util.Set;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
 
public class MyRequest extends HttpServletRequestWrapper {
 
    private HttpServletRequest request = null;
 
    private boolean flag = false;
 
    public MyRequest(HttpServletRequest request) {
        super(request);
        this.request = request;
 
    }
 
    @Override
    public Map<String, String[]> getParameterMap() {
        String method = this.request.getMethod();
        if ("post".equalsIgnoreCase(method)) {
            try {
                request.setCharacterEncoding("utf-8");
            } catch (UnsupportedEncodingException e) {
                e.printStackTrace();
            }
            Map<String, String[]> map = this.request.getParameterMap();
            return map;
 
        } else if ("get".equalsIgnoreCase(method)) {
            Map<String, String[]> map = this.request.getParameterMap();
 
            if (flag) {
                return map;
            }
            if (map == null) {
                return super.getParameterMap();
            } else {
                Set<String> key = map.keySet();
                for (String string : key) {
                    String[] value = map.get(string);
                    for (int i = 0; i < value.length; i++) {
                        try {
                            String string2 = new String(
                                    value[i].getBytes("iso-8859-1"), "utf-8");
                            value[i] = string2;
                        } catch (UnsupportedEncodingException e) {
                            e.printStackTrace();
                        }
                    }
                }
                flag = true;
                return map;
            }
        } else {
            return super.getParameterMap();
        }
    }
 
    @Override
    public String[] getParameterValues(String name) {
        Map<String, String[]> map = this.getParameterMap();
        if (map == null) {
            return super.getParameterValues(name);
        } else {
            String[] strings = map.get(name);
            return strings;
        }
    }
 
    @Override
    public String getParameter(String name) {
        String[] values = this.getParameterValues(name);
        if (values == null) {
            return super.getParameter(name);
        } else {
            return values[0];
        }
    }
 
}

这两个文件放入工程中以后，在web.xml中配置以下代码就可以了。

	<filter>
		<filter-name>characterEncodingFilter</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>
		<init-param>
			<param-name>forceRequestEncoding</param-name>
			<param-value>true</param-value>
		</init-param>
		<init-param>
			<param-name>forceResponseEncoding</param-name>
			<param-value>true</param-value>
		</init-param>
	</filter>
	<filter-mapping>
		<filter-name>characterEncodingFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>