connection的用法 conn = new connection的用法Util().openconnection的用法(); 是什么个用法==

rabbitMQ(4)
java.io.IOException
at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:106)
at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:102)
at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:124)
at com.rabbitmq.client.impl.AMQConnection.start(AMQConnection.java:376)
at com.rabbitmq.client.impl.recovery.RecoveryAwareAMQConnectionFactory.newConnection(RecoveryAwareAMQConnectionFactory.java:36)
at com.rabbitmq.client.impl.recovery.AutorecoveringConnection.init(AutorecoveringConnection.java:83)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:609)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:639)
at cn.fgsw.middleware.rabbitmq.core.DirectProducer.init(DirectProducer.java:88)
at cn.fgsw.middleware.rabbitmq.service.selfProtocal.SelfProtocalProducer.&init&(SelfProtocalProducer.java:37)
at cn..GlobalParam.&clinit&(GlobalParam.java:48)
at cn.fgsw.middleware.start.MiddleWireServer.intParam(MiddleWireServer.java:310)
at cn.fgsw.middleware.start.MiddleWireServer.init(MiddleWireServer.java:54)
at cn.fgsw.middleware.start.MiddleWireServer.main(MiddleWireServer.java:51)
Caused by: com.rabbitmq.client.ShutdownSignalException: connection error
at com.rabbitmq.utility.ValueOrException.getValue(ValueOrException.java:67)
at com.rabbitmq.utility.BlockingValueOrException.uninterruptibleGetValue(BlockingValueOrException.java:33)
at com.rabbitmq.client.impl.AMQChannel$BlockingRpcContinuation.getReply(AMQChannel.java:343)
at com.rabbitmq.client.impl.AMQChannel.privateRpc(AMQChannel.java:216)
at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:118)
... 11 more
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:189)
at java.net.SocketInputStream.read(SocketInputStream.java:121)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:235)
at java.io.BufferedInputStream.read(BufferedInputStream.java:254)
at java.io.DataInputStream.readUnsignedByte(DataInputStream.java:288)
at com.rabbitmq.client.impl.Frame.readFrom(Frame.java:95)
at com.rabbitmq.client.impl.SocketFrameHandler.readFrame(SocketFrameHandler.java:139)
at com.rabbitmq.client.impl.AMQConnection$MainLoop.run(AMQConnection.java:534)
at java.lang.Thread.run(Thread.java:722)
java.io.IOException
at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:106)
at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:102)
at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:124)
at com.rabbitmq.client.impl.AMQConnection.start(AMQConnection.java:376)
at com.rabbitmq.client.impl.recovery.RecoveryAwareAMQConnectionFactory.newConnection(RecoveryAwareAMQConnectionFactory.java:36)
at com.rabbitmq.client.impl.recovery.AutorecoveringConnection.init(AutorecoveringConnection.java:83)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:609)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:639)
at cn.fgsw.middleware.rabbitmq.core.DirectProducer.init(DirectProducer.java:88)
at cn.fgsw.middleware.rabbitmq.service.fourxin.FourxxAnswerProducer.&init&(FourxxAnswerProducer.java:40)
at cn..GlobalParam.&clinit&(GlobalParam.java:49)
at cn.fgsw.middleware.start.MiddleWireServer.intParam(MiddleWireServer.java:310)
at cn.fgsw.middleware.start.MiddleWireServer.init(MiddleWireServer.java:54)
at cn.fgsw.middleware.start.MiddleWireServer.main(MiddleWireServer.java:51)
Caused by: com.rabbitmq.client.ShutdownSignalException: connection error
at com.rabbitmq.utility.ValueOrException.getValue(ValueOrException.java:67)
at com.rabbitmq.utility.BlockingValueOrException.uninterruptibleGetValue(BlockingValueOrException.java:33)
at com.rabbitmq.client.impl.AMQChannel$BlockingRpcContinuation.getReply(AMQChannel.java:343)
at com.rabbitmq.client.impl.AMQChannel.privateRpc(AMQChannel.java:216)
at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:118)
... 11 more
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:189)
at java.net.SocketInputStream.read(SocketInputStream.java:121)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:235)
at java.io.BufferedInputStream.read(BufferedInputStream.java:254)
at java.io.DataInputStream.readUnsignedByte(DataInputStream.java:288)
at com.rabbitmq.client.impl.Frame.readFrom(Frame.java:95)
at com.rabbitmq.client.impl.SocketFrameHandler.readFrame(SocketFrameHandler.java:139)
at com.rabbitmq.client.impl.AMQConnection$MainLoop.run(AMQConnection.java:534)
at java.lang.Thread.run(Thread.java:722)
this.queueName=ps62xxAnswer this.topic=ps62xxAnswer
java.io.IOException
at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:106)
at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:102)
at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:124)
at com.rabbitmq.client.impl.AMQConnection.start(AMQConnection.java:376)
at com.rabbitmq.client.impl.recovery.RecoveryAwareAMQConnectionFactory.newConnection(RecoveryAwareAMQConnectionFactory.java:36)
at com.rabbitmq.client.impl.recovery.AutorecoveringConnection.init(AutorecoveringConnection.java:83)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:609)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:639)
at cn.fgsw.middleware.rabbitmq.core.DirectProducer.init(DirectProducer.java:88)
at cn.fgsw.middleware.rabbitmq.service.data62xx.PingSheng62xxAnswerProducer.&init&(PingSheng62xxAnswerProducer.java:39)
at cn..GlobalParam.&clinit&(GlobalParam.java:50)
at cn.fgsw.middleware.start.MiddleWireServer.intParam(MiddleWireServer.java:310)
at cn.fgsw.middleware.start.MiddleWireServer.init(MiddleWireServer.java:54)
at cn.fgsw.middleware.start.MiddleWireServer.main(MiddleWireServer.java:51)
Caused by: com.rabbitmq.client.ShutdownSignalException: connection error
at com.rabbitmq.utility.ValueOrException.getValue(ValueOrException.java:67)
at com.rabbitmq.utility.BlockingValueOrException.uninterruptibleGetValue(BlockingValueOrException.java:33)
at com.rabbitmq.client.impl.AMQChannel$BlockingRpcContinuation.getReply(AMQChannel.java:343)
at com.rabbitmq.client.impl.AMQChannel.privateRpc(AMQChannel.java:216)
at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:118)
... 11 more
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:189)
at java.net.SocketInputStream.read(SocketInputStream.java:121)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:235)
at java.io.BufferedInputStream.read(BufferedInputStream.java:254)
at java.io.DataInputStream.readUnsignedByte(DataInputStream.java:288)
at com.rabbitmq.client.impl.Frame.readFrom(Frame.java:95)
at com.rabbitmq.client.impl.SocketFrameHandler.readFrame(SocketFrameHandler.java:139)
at com.rabbitmq.client.impl.AMQConnection$MainLoop.run(AMQConnection.java:534)
at java.lang.Thread.run(Thread.java:722)
this.queueName=ps63xxAnswer this.topic=ps63xxAnswer
java.io.IOException
at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:106)
at com.rabbitmq.client.impl.AMQChannel.wrap(AMQChannel.java:102)
at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:124)
at com.rabbitmq.client.impl.AMQConnection.start(AMQConnection.java:376)
at com.rabbitmq.client.impl.recovery.RecoveryAwareAMQConnectionFactory.newConnection(RecoveryAwareAMQConnectionFactory.java:36)
at com.rabbitmq.client.impl.recovery.AutorecoveringConnection.init(AutorecoveringConnection.java:83)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:609)
at com.rabbitmq.client.ConnectionFactory.newConnection(ConnectionFactory.java:639)
at cn.fgsw.middleware.rabbitmq.core.DirectProducer.init(DirectProducer.java:88)
at cn.fgsw.middleware.rabbitmq.service.data6311.PingSheng6311AnswerProducer.&init&(PingSheng6311AnswerProducer.java:40)
at cn..GlobalParam.&clinit&(GlobalParam.java:51)
at cn.fgsw.middleware.start.MiddleWireServer.intParam(MiddleWireServer.java:310)
at cn.fgsw.middleware.start.MiddleWireServer.init(MiddleWireServer.java:54)
at cn.fgsw.middleware.start.MiddleWireServer.main(MiddleWireServer.java:51)
Caused by: com.rabbitmq.client.ShutdownSignalException: connection error
at com.rabbitmq.utility.ValueOrException.getValue(ValueOrException.java:67)
at com.rabbitmq.utility.BlockingValueOrException.uninterruptibleGetValue(BlockingValueOrException.java:33)
at com.rabbitmq.client.impl.AMQChannel$BlockingRpcContinuation.getReply(AMQChannel.java:343)
at com.rabbitmq.client.impl.AMQChannel.privateRpc(AMQChannel.java:216)
at com.rabbitmq.client.impl.AMQChannel.exnWrappingRpc(AMQChannel.java:118)
... 11 more
Caused by: java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:189)
at java.net.SocketInputStream.read(SocketInputStream.java:121)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:235)
at java.io.BufferedInputStream.read(BufferedInputStream.java:254)
at java.io.DataInputStream.readUnsignedByte(DataInputStream.java:288)
at com.rabbitmq.client.impl.Frame.readFrom(Frame.java:95)
at com.rabbitmq.client.impl.SocketFrameHandler.readFrame(SocketFrameHandler.java:139)
at com.rabbitmq.client.impl.AMQConnection$MainLoop.run(AMQConnection.java:534)
at java.lang.Thread.run(Thread.java:722)
发生这种情况,除了是用户、密码、端口的出错外,还有就是在设置用户时,没有点击set permission了
参考知识库
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17:07 by shy.ang, ... 阅读,
  &&作为一个初学者,我是在学习Android网络编程的时候遇到的URLConnection,在网上也看见了不少代码,发现他们写的都不一样,或多或少(除了转载),也有很多提问和回答的,自己从中也吸取了一些知识,再加上自己的理解和调试,得出了一些东西,整理一下吧。
  对于Android的初学者,在网络编程的时候,一定不要忘记&uses-permission android:name="android.permission.INTERNET"&&/uses-permission&,我在这上面吃了两次亏,比较郁闷,希望大家尤其是初学者千万不要忘记!不添加的话,貌似由对应程序调出的Andorid模拟器会显示网络没有信号,即上不去网。
  关于URLConnection,网上很多回答都是对API的翻译,很崩溃,我是看了很多之后,然后看API才发现的。此后我会吸取教训,一遇到问题首先看API,也建议大家这样,英文的最好,不是太相信那些翻译的,呵呵,感觉还是自己斟酌理解的好吧。下面我就解读一下URLConnection的API,虽然也是一种翻译,但是结合我自己的理解,还有一点亲自调试得出的结论。
  URLConnection是所有表示应用程序与URL之间通信连接的类的父类(super class),该类的实例可以用来对由URL引用的资源进行读取和写入操作。
  HttpURLConnection 是支持HTTP特定功能的URLConnection,还有JarConnection是URLConnection的直接子类。
  创建URLConnection对象主要要经历两步:
      第一步是creat:URLConnection conn = url.openConnection();
      第二步是connect:conn.connect();//这两个是不同的,见下面调试
       在created和connected之间可以设置一些变量选项(如setDoInput,超时等),而如果connect之后再设置就会引发异常(网上也有这个问题)
      在需要连接才能执行的操作(如getInputStream等应用层操作),程序会暗中(implicitly)执行连接
      一旦连接可用,就可以访问获取资源,如执行getInputStream()等,对于HttpURLConnection,还有conn.getResponseCode()==200来判定服务器是否返回正确的应答码以表明请求被接受。
  在URLConnection中,有一个域boolean connected ,值为true表明已经建立到指定URL的连接;false则没有(华丽的标记)
  connect() & &当连接还未被建立时,打开一个communications link,而如果这个链接已经被打开(connected值设置为true)则 ignore it 。
  下面编了一个小程序进行调试:
URL url = new URL("");URLConnection conn = url.openConnection();conn.setConnectTimeout(10000);conn.connect();InputStream inStream = conn.getInputStream();
当程序执行完openConnection()之后,域connected值还是false,说明这时候还未连接。等执行到connect()之后,connected才变为true,说明这时候才完成连接。而当我注释掉connect()后,再运行程序,connected值到getInputStream执行完又变为true,这时候知道getInputStream会使连接暗中被执行。
  综上,对于一般需要连接才执行的操作(可能也有不需要连接的操作吧~~),connect()是可以省略的。但是只有在connect()执行完,连接才正式建立,而不是openConnection(只是创建了一个连接对象)
  (后记)可以利用ByteArrayOutputStream将输入流写入内存:
ByteArrayOutputStream outstream=new ByteArrayOutputStream();
byte[] buffer=new byte[1024];
int len=-1;
while((len=inStream.read(buffer)) !=-1){
outstream.write(buffer, 0, len);
outstream.close();
inStream.close();using (SqlConnection conn = new SqlConnection(_connstr))_百度知道
using (SqlConnection conn = new SqlConnection(_connstr))
using (SqlConnection conn = new SqlConnection(_connstr)) 这个using
有什么作用?
提问者采纳
using就是调用的意思,就是说在接下来using的代码范围内你能使用conn这个对象,一旦你超出了using的代码范围,就没得conn这个对象给你用了
提问者评价
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其他4条回答
相当于在using块结束的时候手动调用conn.Dispose()方法!属于优化资源配置!^_^
意思是,退出using后,会自动调用conn的Dispose方法。
当using里的代码都运行完了就将conn的连接关闭
就是把图片以二进制存储到数据库,具体方法可见
1、建所需数据库和表,语句如下:
--建立数据库
create database test
--使用该数据库
--建立存放图片的表
create table piclist(
id int Identity primary key,
pic Image not null
2、制作上传图片的模块,代码如下:
前台html代码:
&%@ Page Language=&C#& AutoEventWireup=&true& CodeFile=&UpPhoto.aspx.cs& Inherits=&Test_UpPhoto& %&
&!DOCTYPE html PUBLIC &-//W3C//DTD XHTML 1.0 Transitional//EN& &&&
&html xmlns=&& &
&head runat=&server&&
&title&无标题页&/title&
&form id=&form1& runat=&server&&
sqlconnection的相关知识
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出门在外也不愁.NET中using(SqlConnection conn = new SqlConnection(connectionStr))解释这种using用法什么意思_百度知道
.NET中using(SqlConnection conn = new SqlConnection(connectionStr))解释这种using用法什么意思
using是一种方便的简写形式。当某个类型实现了IDisposable接口时,在使用这样的类型时就可以用using。它等价于:SqlConnection conn = new SqlConnection(connectionStr);....conn.Dispose();//这个Dispose就是从IDisposable接口实现的方法。这个方法一般做一些清理工作
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这种写法的意思是,语句执行完之后,自动关闭并回收这个SqlConnection对象。
using就是调用的意思,就是说在接下来using的代码范围内你能使用conn这个对象,一旦你超出了using的代码范围,就没得conn这个对象给你用了 意思是,
sqlconnection的相关知识
等待您来回答
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出门在外也不愁using(conn)是什么意思?怎么用?最好举例说明一下.看见这么一段代码:SqlCommand cmd = new SqlCommand();cmd.Connection =mandText = "insert into tableA values(1,'a','b');using (conn){conn.Open();cmd.ExecuteNonQuery();}不是很明白,我在using外可可以访问到conn,那这么写的话这个using还有什么意义啊?
using(conn){conn.Open();cmd.ExecuteNonQuery();}的作用是确保在跳出大括号时,能释放conn对象占用的资源等效于:conn.Open();cmd.ExecuteNonQuery();conn.Close();但是,using写法即使大括号里出现了异常,也能确保关闭连接,而后面一种写法,如果代码出现了异常,可能导致连接无法关闭
如果在using外写conn.Open();如:
conn.Open();
using(conn)
cmd.ExecuteNonQuery();
大括号里边出现异常,conn对象也能释放么?
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