Java相关问题整理

1. okhttpclient调用出现大量close_wait。

问题定位：

　　凡是系统中出现大量的close_wait，说明你的代码写的有问题，即：没有关闭连接。

在okhttpclient中，默认时 http头字段 connection 设置值为keep-alive，这样会导致服务端断开连接时，客户端不能及时的断开连接，从而出现大量的close_wait。

问题修改：

　　把http头字段 connection 设置值为close

 

如下是一段短连接http调用代码。

package com.xman.httpclient;

import okhttp3.*;
import org.springframework.stereotype.service;

import java.io.ioexception;
import java.util.concurrent.timeunit;

/**
 * created by wangyaofu on 2018/4/25.
 */
@service
public class httpserviceimpl {

    public final static int connect_timeout =10000;
    public final static int read_timeout=10000;
    public final static int write_timeout=10000;

    public string httpget(string url, string useragent) {
            final request request = new request.builder()
                    .url(url).header("user-agent", useragent).header("connection", "close")
                    .build();
            okhttpclient okhttpclient = new okhttpclient.builder()
                    .readtimeout(read_timeout, timeunit.milliseconds)
                    .writetimeout(write_timeout, timeunit.milliseconds)
                    .connecttimeout(connect_timeout, timeunit.milliseconds)
                    .build();
        response response;
        try {
            response = okhttpclient.newcall(request).execute();
            return response.body().string();
        } catch (exception e) {
            //logger.error("httpget err=" + e.getmessage());
        }
        return null;
    }

    public string httppost(string url, string body) {
        requestbody requestbody = requestbody.create(mediatype.parse("application/json; charset=utf-8"), body);
        //创建一个请求对象
        request request = new request.builder()
                .url(url).header("connection", "close")
                .post(requestbody)
                .build();
        //发送请求获取响应
        try {
            okhttpclient okhttpclient = new okhttpclient.builder()
                    .readtimeout(read_timeout, timeunit.milliseconds)
                    .writetimeout(write_timeout, timeunit.milliseconds)
                    .connecttimeout(connect_timeout, timeunit.milliseconds)
                    .build();
            response response=okhttpclient.newcall(request).execute();
            if (response != null && response.body() != null) {
                return response.body().string();
            }
        } catch (exception e) {
            //logger.error("httppost err=" + e.getmessage());
        }
        return null;
    }
}