解决使用@ResponseBody后返回500错误的问题
在springmvc+mybatis的项目中,利用mybatis分页插件mybatis-paginator进行分页查询,结果出现了500异常,后端又没有明显的报错。
原来的写法,返回Map对象,由springmvc里面的机制转为json对象,这样就会导致,在转json过程中的报错,都隐藏了,无法抛出,前端获取不到正确的数据,
最后就出现了500的异常。
@RequestMapping(value = "/query") @ResponseBody public Map<String, Object> data(HttpServletRequest request, HttpServletResponse response, CreditloanInfoParams params) { Map<String, Object> data = new HashMap<String, Object>(); if(params==null){ params=new CreditloanInfoParams(); } PageList<CreditloanInfo> list = (PageList<CreditloanInfo>) creditloanInfoService.getCreditloanInfoListData(params); data.put("total", list.getPaginator().getTotalCount()); data.put("rows", list); return data; }
改成使用fastJson主动转化为json格式的字符串,这样的好处是,转json过程中如果出现错误,会有很明确的提示。
@SuppressWarnings("unchecked") @RequestMapping(value = "/query") @ResponseBody public String data(HttpServletRequest request, HttpServletResponse response, BlackParams params) { //Map<String, Object> data = new HashMap<String, Object>(); /*PageList<Blacklist> blackDatas = (PageList<Blacklist>) blackService.getPageData(params); data.put("total", blackDatas.getPaginator().getTotalCount()); data.put("rows", blackDatas);*/ //blackService.getPageData(params); /* Map data = new HashMap(); PageList<Blacklist> blackDatas = blackService.getBlackListData(params); data.put("total", blackDatas.getPaginator().getTotalCount()); data.put("rows", blackDatas);*/ return JSON.toJSONString(blackService.getPageData(params)); }
最后发现是转json中出现了空指针异常。修复后,问题解决。
补充知识:springboot 使用过滤器获取response内容保存接口访问日志
一、创建过滤器
1. 在spring boot的启动入口出添加注解 @ServletComponentScan
@SpringBootApplication @ServletComponentScan public class Application { public static void main(String[] args) { SpringApplication.run(Applicatioin.class, args); } }
2.新建过滤器AccessLogFilter.java
@WebFilter(filterName = "accessLog", urlPatterns = "/api/*") public class AccessLogFilter implements Filter { @Autowired AccessLogMapper accessLogMapper; public void destroy() { } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { long startTime = System.currentTimeMillis(); ResponseWrapper wrapper = new ResponseWrapper((HttpServletResponse) response); HttpServletRequest req = (HttpServletRequest) request; chain.doFilter(request, wrapper); long endTime = System.currentTimeMillis(); Gson gson = new Gson(); // 获取response返回的内容并重新写入response String result = wrapper.getResponseData(response.getCharacterEncoding()); response.getOutputStream().write(result.getBytes()); String uri = req.getRequestURI(); AccessLog log = new AccessLog(); log.setMethod(req.getMethod()); log.setUrl(uri); log.setParameters(gson.toJson(req.getParameterMap())); log.setResponseCode(String.valueOf(wrapper.getStatus())); log.setResult(result); log.setCreateDatetime(new Date()); log.setTimeConsuming((int)(endTime - startTime)); accessLogMapper.insertSelective(log); } public void init(FilterConfig fConfig) throws ServletException { } }
这个过滤器使用了注解@WebFilter(filterName = "accessLog", urlPatterns = "/api/*") 进行配置,指定了url进入规则,只有以/api/开头的url才能进入到此过滤器中。在doFilter方法中使用了自定义的ResponseWrapper对response进行封装。Controller接口走完之后获取到接口返回的数据并再次封装到response。
3. ResponseWrapper.java 类
import java.io.ByteArrayOutputStream; import java.io.CharArrayWriter; import java.io.IOException; import java.io.OutputStreamWriter; import java.io.PrintWriter; import java.io.UnsupportedEncodingException; import javax.servlet.ServletOutputStream; import javax.servlet.WriteListener; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpServletResponseWrapper; public class ResponseWrapper extends HttpServletResponseWrapper { private ByteArrayOutputStream buffer = null; private ServletOutputStream out = null; private PrintWriter writer = null; public ResponseWrapper(HttpServletResponse response) throws IOException{ super(response); buffer = new ByteArrayOutputStream(); out = new WapperedOutputStream(buffer); writer = new PrintWriter(new OutputStreamWriter(buffer, "UTF-8")); } //重载父类获取outputstream的方法 @Override public ServletOutputStream getOutputStream() throws IOException { return out; } @Override public PrintWriter getWriter() throws IOException { return writer; } @Override public void flushBuffer() throws IOException { if (out != null) { out.flush(); } if (writer != null) { writer.flush(); } } @Override public void reset() { buffer.reset(); } public String getResponseData(String charset) throws IOException { flushBuffer();//将out、writer中的数据强制输出到WapperedResponse的buffer里面,否则取不到数据 byte[] bytes = buffer.toByteArray(); try { return new String(bytes, "UTF-8"); } catch (UnsupportedEncodingException e) { return ""; } } //内部类,对ServletOutputStream进行包装,指定输出流的输出端 private class WapperedOutputStream extends ServletOutputStream { private ByteArrayOutputStream bos = null; public WapperedOutputStream(ByteArrayOutputStream stream) throws IOException { bos = stream; } //将指定字节写入输出流bos @Override public void write(int b) throws IOException { bos.write(b); } @Override public boolean isReady() { // TODO Auto-generated method stub return false; } @Override public void setWriteListener(WriteListener listener) { // TODO Auto-generated method stub } } }
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