通过HttpServletResponseWrapper修改response输出流

在项目中遇到一个问题，需要对接口返回的数据进行加密给前端。项目中的controller一般都是返回一个实体form，重写的一个视图解析器继承ModelAndViewResolver，对返回的form转成json格式返回给前端。

视图解析器：

public class JsonModelAndViewResolver implements ModelAndViewResolver,
		InitializingBean, ApplicationContextAware {
	private String defaultContentType = "text/html";
	private Log log = LogFactory.getLog(super.getClass());
	private JsonSerialization jsonSerialization;
	private ApplicationContext applicationContext;

	public void afterPropertiesSet() throws Exception {
		if (this.jsonSerialization != null)
			return;
		this.jsonSerialization = JsonSerializationFactory.getInstance(this.applicationContext);
	}

	public void setApplicationContext(ApplicationContext paramApplicationContext)
			throws BeansException {
		this.applicationContext = paramApplicationContext;
	}

	//执行这个方法
	public ModelAndView resolveModelAndView(Method paramMethod,
			Class paramClass, Object paramObject,
			ExtendedModelMap paramExtendedModelMap,
			NativeWebRequest paramNativeWebRequest) {
		if (Rest.class.isAssignableFrom(paramClass)) {
			try {
				HttpServletResponse localHttpServletResponse = (HttpServletResponse) paramNativeWebRequest.getNativeResponse(HttpServletResponse.class);
				responseJson(paramObject, localHttpServletResponse);
			} catch (IOException localIOException) {
				throw new WebException(localIOException.getMessage(),
						localIOException);
			}
			return null;
		}
		return UNRESOLVED;
	}

	public void responseJson(Object paramObject,
			HttpServletResponse paramHttpServletResponse) throws IOException {
		if (!(StringUtils.hasText(paramHttpServletResponse.getContentType())))
			paramHttpServletResponse.setContentType(this.defaultContentType);
		String str = writeResult(paramObject);
		PrintWriter localPrintWriter = paramHttpServletResponse.getWriter();
		if (this.log.isInfoEnabled())
			this.log.info("Rest result=" + str);
		if ("{}".equals(str)) {
			this.log.info("image stream is not write ");
			return;
		}
		localPrintWriter.write(str);
		localPrintWriter.flush();
	}

	protected String writeResult(Object paramObject) {
		String str = null;
		if (paramObject == null) {
			str = "{}";
		} else if ((paramObject instanceof Number)
				|| (paramObject instanceof Boolean)) {
			str = "{\"resultCode\":\"" + paramObject.toString() + "\"}";
		} else if ((paramObject instanceof String)) {
			String result = (String) paramObject;
			str = result;
		} else {
			if (paramObject instanceof ModelAndView)
				paramObject = ((ModelAndView) paramObject).getModel();
			str = getJsonSerialization().toJSONString(paramObject);
		}
		return str;
	}

	public String getDefaultContentType() {
		return this.defaultContentType;
	}

	public void setDefaultContentType(String paramString) {
		this.defaultContentType = paramString;
	}

	public JsonSerialization getJsonSerialization() {
		return this.jsonSerialization;
	}

	public void setJsonSerialization(JsonSerialization paramJsonSerialization) {
		this.jsonSerialization = paramJsonSerialization;
	}
}

　　本来考虑直接修改视图解析器，对返回json串加密，但发现项目中有些接口直接在controller中直接通过PrintWriter返回了参数，显然有这种方法是拦截不到的。

最后通过HttpServletResponseWrapper截取返回数据流加密重新输出给前端的方式。

代码参照如下：

ResponseWrapper:

package com.paic.egis.smts.toa.web.interceptor;

import java.io.CharArrayWriter;
import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

import com.paic.egis.smts.common.util.LoggerUtil;

public class ResponseWrapper extends HttpServletResponseWrapper {
	private PrintWriter cachedWriter;
	private CharArrayWriter bufferedWriter;

	public ResponseWrapper(HttpServletResponse response) throws IOException {
		super(response);
		bufferedWriter = new CharArrayWriter();
		cachedWriter = new PrintWriter(bufferedWriter);
	}

	public PrintWriter getWriter() throws IOException {
		return cachedWriter;
	}

	public String getResult() {
		byte[] bytes = bufferedWriter.toString().getBytes();
		try {
			return new String(bytes, "UTF-8");
		} catch (Exception e) {
			LoggerUtil.logError(this.getClass().getName(), "getResult", e);
			return "";
		}
	}

}

　　过滤器如下：

package com.paic.egis.smts.toa.web.filter;

import java.io.IOException;
import java.io.PrintWriter;

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.http.HttpServletResponse;

import com.alibaba.dubbo.common.utils.StringUtils;
import com.paic.egis.smts.common.util.LoggerUtil;
import com.paic.egis.smts.common.util.PropertiesUtil;
import com.paic.egis.smts.pama.security.Base64Utils;
import com.paic.egis.smts.toa.web.interceptor.ResponseWrapper;
import com.paic.egis.smts.trusteesship.util.RSACoder;

public class ResponseWrapperFilter implements Filter {

	public void destroy() {

	}

	public void doFilter(ServletRequest req, ServletResponse resp,
			FilterChain chain) throws IOException, ServletException {

		String version = req.getParameter("version");
		if(StringUtils.isEmpty(version)){

			chain.doFilter(req, resp);

		} else {

			HttpServletResponse response = (HttpServletResponse) resp;
			ResponseWrapper mr = new ResponseWrapper(response);

			chain.doFilter(req, mr);

			PrintWriter out = resp.getWriter();
			try {
				//取返回的json串
				String result = mr.getResult();
				System.out.println(result);
				//加密
				String encryptStr = encryptRSA(result);
				out.write(encryptStr);
			} catch (Exception e) {
				LoggerUtil.logError(this.getClass().getName(), "doFilter", e);
			} finally {
				out.flush();
				out.close();
			}
		}
	}

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

	}

	//rsa公钥加密
	public String encryptRSA(String content) throws Exception{
		String publicKeyStr = PropertiesUtil.getProperty("response.publicKey");
		byte[] encryptBytes = RSACoder.encrypt(content.getBytes("utf-8"), publicKeyStr,"public");
		return  Base64Utils.encode(encryptBytes);
	}
}