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HTTP Status Codes Explained
All valid HTTP 1.1 Status Codes simply explained.
HTTP, Hypertext Transfer Protocol, is the method by which clients (i.e. you) and servers communicate. When someone clicks a link, types in a URL or submits out a form, their browser sends a request to a server for information. It might be asking for a page, or sending data, but either way, that is called an HTTP Request. When a server receives that request, it sends back an HTTP Response, with information for the client. Usually, this is invisible, though I'm sure you've seen one of the very common Response codes - 404, indicating a page was not found. There are a fair few more status codes sent by servers, and the following is a list of the current ones in HTTP 1.1, along with an explanation of their meanings.
A more technical breakdown of HTTP 1.1 status codes and their meanings is available at http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html. There are several versions of HTTP, but currently HTTP 1.1 is the most widely used.
Informational
- 100 - Continue
A status code of 100 indicates that (usually the first) part of a request has been received without any problems, and that the rest of the request should now be sent.
- 101 - Switching Protocols
HTTP 1.1 is just one type of protocol for transferring data on the web, and a status code of 101 indicates that the server is changing to the protocol it defines in the "Upgrade" header it returns to the client. For example, when requesting a page, a browser might receive a statis code of 101, followed by an "Upgrade" header showing that the server is changing to a different version of HTTP.
Successful
- 200 - OK
The 200 status code is by far the most common returned. It means, simply, that the request was received and understood and is being processed.
- 201 - Created
A 201 status code indicates that a request was successful and as a result, a resource has been created (for example a new page).
- 202 - Accepted
The status code 202 indicates that server has received and understood the request, and that it has been accepted for processing, although it may not be processed immediately.
- 203 - Non-Authoritative Information
A 203 status code means that the request was received and understood, and that information sent back about the response is from a third party, rather than the original server. This is virtually identical in meaning to a 200 status code.
- 204 - No Content
The 204 status code means that the request was received and understood, but that there is no need to send any data back.
- 205 - Reset Content
The 205 status code is a request from the server to the client to reset the document from which the original request was sent. For example, if a user fills out a form, and submits it, a status code of 205 means the server is asking the browser to clear the form.
- 206 - Partial Content
A status code of 206 is a response to a request for part of a document. This is used by advanced caching tools, when a user agent requests only a small part of a page, and just that section is returned.
Redirection
- 300 - Multiple Choices
The 300 status code indicates that a resource has moved. The response will also include a list of locations from which the user agent can select the most appropriate.
- 301 - Moved Permanently
A status code of 301 tells a client that the resource they asked for has permanently moved to a new location. The response should also include this location. It tells the client to use the new URL the next time it wants to fetch the same resource.
- 302 - Found
A status code of 302 tells a client that the resource they asked for has temporarily moved to a new location. The response should also include this location. It tells the client that it should carry on using the same URL to access this resource.
- 303 - See Other
A 303 status code indicates that the response to the request can be found at the specified URL, and should be retrieved from there. It does not mean that something has moved - it is simply specifying the address at which the response to the request can be found.
- 304 - Not Modified
The 304 status code is sent in response to a request (for a document) that asked for the document only if it was newer than the one the client already had. Normally, when a document is cached, the date it was cached is stored. The next time the document is viewed, the client asks the server if the document has changed. If not, the client just reloads the document from the cache.
- 305 - Use Proxy
A 305 status code tells the client that the requested resource has to be reached through a proxy, which will be specified in the response.
- 307 - Temporary Redirect
307 is the status code that is sent when a document is temporarily available at a different URL, which is also returned. There is very little difference between a 302 status code and a 307 status code. 307 was created as another, less ambiguous, version of the 302 status code.
Client Error
- 400 - Bad Request
A status code of 400 indicates that the server did not understand the request due to bad syntax.
- 401 - Unauthorized
A 401 status code indicates that before a resource can be accessed, the client must be authorised by the server.
- 402 - Payment Required
The 402 status code is not currently in use, being listed as "reserved for future use".
- 403 - Forbidden
A 403 status code indicates that the client cannot access the requested resource. That might mean that the wrong username and password were sent in the request, or that the permissions on the server do not allow what was being asked.
- 404 - Not Found
The best known of them all, the 404 status code indicates that the requested resource was not found at the URL given, and the server has no idea how long for.
- 405 - Method Not Allowed
A 405 status code is returned when the client has tried to use a request method that the server does not allow. Request methods that are allowed should be sent with the response (common request methods are POST and GET).
- 406 - Not Acceptable
The 406 status code means that, although the server understood and processed the request, the response is of a form the client cannot understand. A client sends, as part of a request, headers indicating what types of data it can use, and a 406 error is returned when the response is of a type not i that list.
- 407 - Proxy Authentication Required
The 407 status code is very similar to the 401 status code, and means that the client must be authorised by the proxy before the request can proceed.
- 408 - Request Timeout
A 408 status code means that the client did not produce a request quickly enough. A server is set to only wait a certain amount of time for responses from clients, and a 408 status code indicates that time has passed.
- 409 - Conflict
A 409 status code indicates that the server was unable to complete the request, often because a file would need to be editted, created or deleted, and that file cannot be editted, created or deleted.
- 410 - Gone
A 410 status code is the 404's lesser known cousin. It indicates that a resource has permanently gone (a 404 status code gives no indication if a resource has gine permanently or temporarily), and no new address is known for it.
- 411 - Length Required
The 411 status code occurs when a server refuses to process a request because a content length was not specified.
- 412 - Precondition Failed
A 412 status code indicates that one of the conditions the request was made under has failed.
- 413 - Request Entity Too Large
The 413 status code indicates that the request was larger than the server is able to handle, either due to physical constraints or to settings. Usually, this occurs when a file is sent using the POST method from a form, and the file is larger than the maximum size allowed in the server settings.
- 414 - Request-URI Too Long
The 414 status code indicates the the URL requested by the client was longer than it can process.
- 415 - Unsupported Media Type
A 415 status code is returned by a server to indicate that part of the request was in an unsupported format.
- 416 - Requested Range Not Satisfiable
A 416 status code indicates that the server was unable to fulfill the request. This may be, for example, because the client asked for the 800th-900th bytes of a document, but the document was only 200 bytes long.
- 417 - Expectation Failed
The 417 status code means that the server was unable to properly complete the request. One of the headers sent to the server, the "Expect" header, indicated an expectation the server could not meet.
Server Error
- 500 - Internal Server Error
A 500 status code (all too often seen by Perl programmers) indicates that the server encountered something it didn't expect and was unable to complete the request.
- 501 - Not Implemented
The 501 status code indicates that the server does not support all that is needed for the request to be completed.
- 502 - Bad Gateway
A 502 status code indicates that a server, while acting as a proxy, received a response from a server further upstream that it judged invalid.
- 503 - Service Unavailable
A 503 status code is most often seen on extremely busy servers, and it indicates that the server was unable to complete the request due to a server overload.
- 504 - Gateway Timeout
A 504 status code is returned when a server acting as a proxy has waited too long for a response from a server further upstream.
- 505 - HTTP Version Not Supported
A 505 status code is returned when the HTTP version indicated in the request is no supported. The response should indicate which HTTP versions are supported.
摘要: 一、往串口写数据
import java.io.*;
import javax.comm.*;
import java.util.*;
public class PortWriter
{
static Enumeration ports;
... 阅读全文
"java decompiler"是一个非常出色的java反编译工具，详见主页：http://java.decompiler.free.fr/
在myeclipse8.5中的安装也比较简单，下载：http://java.decompiler.free.fr/jd-eclipse/update/jdeclipse_update_site.zip
然后把这个压缩包解开放在myeclipse8.5的dropins目录下，比如：C:\Programs\Genuitec\MyEclipse-8.5\dropins\jdeclipse_update_site
重起myeclipse就行了，第一次打开class文件，可能会稍微有一点慢，要等待一小会才会反编译出来。
好像还有点问题
操作系统升级到windows7之后，原来很多软件就不能用了。对于虚拟光驱软件，我推荐一款免费的：WinCDEmu，这是一个在SourceForge上的免费软件。优点是使用方便，他可以虚拟出任意多个虚拟光驱，而且可以选择手工指定盘符。只要双击文件，就会弹出一个对话框，询问光驱的盘符。当然你也可以选择让WinCDEmu自动选择盘符。他支持大部分主流的文件格式： ISO, CUE, NRG, MDS/MDF, CCD, IMG
Recently I got a chance working with Spring security, formerly known as Acegi Security for spring. While working with the framework, I heard comments from friends and colleagues saying that spring security lacks proper documentation. So thought of sharing a little knowledge. By the way, this is first ever blog posting and kindly excuse me and let me know any errors and improvements.
Spring security offers a simple configuration based security for your web applications helping you secure your web application with out littering your business logic with any security code. It provides securing URL's based on the Role (Authorities), securing your business methods based on the ACL's.
The first step in hooking up the spring security to your web application is by specifying the DelegatingFilterProxy in your web.xml.
springSecurityFilterChain
org.springframework.web.filter.DelegatingFilterProxy
springSecurityFilterChain
/*
REQUEST
INCLUDE
FORWARD
If you want to externalize all of your security related configuration into a separate file, you can do so and add that to your context location param.
contextConfigLocation
/WEB-INF/beans.xml , /WEB-INF/springSecurity.xml
Now comes the part of security configuration for your application, Adding the URL security patterns is pretty simple and straight forward. Add all the URL patterns which you want to secure and add the wild card pattern at the end. You need to have some default principal and role even for non logged in users as you need to give access to pages like log in, register and forgot password kind of functionality even to non logged in users.
I tried to add comments to pretty much every element which I am using here.
As an example I added just a wild card intercept url which make every page of my application secure. You need to exclude different urls based on the roles.
Following is my custom implementation of AuthenticationEntryPoint, which currently is not doing any thing except leveraging the commence to its super class which is the spring implementation of AuthenticationProcessingFilterEntryPoint. I hooked it to add any custom logic.
public class CustomAuthenticationEntryPoint extends AuthenticationProcessingFilterEntryPoint {
private static final Log logger = LogFactory.getLog(CustomAuthenticationEntryPoint.class);
@Override
public void commence(ServletRequest request, ServletResponse response, AuthenticationException authException) throws IOException, ServletException {
super.commence(request, response, authException);
}
}
This is my custom authentication manager which actually does the custom login of the user. It will throw an BadCredentialsException in case of invalid credentials or thorws a AuthenticationServiceException in case of a service error (Database error, SQL error or any other error).
public class CustomAuthunticationManager implements AuthenticationManager {
@Autowired
UserManagerService userManagerService;
public Authentication authenticate(Authentication authentication) throws AuthenticationException {
if(StringUtils.isBlank((String) authentication.getPrincipal()) || StringUtils.isBlank((String) authentication.getCredentials())){
throw new BadCredentialsException("Invalid username/password");
}
User user = null;
GrantedAuthority[] grantedAuthorities = null;
try{
user = userManagerService.getUser((String) authentication.getPrincipal(), (String) authentication.getCredentials());
}
catch(InvalidCredentialsException ex){
throw new BadCredentialsException(ex.getMessage());
}
catch(Exception e){
throw new AuthenticationServiceException("Currently we are unable to process your request. Kindly try again later.");
}
if (user != null) {
List roles = user.getAssociatedRoles();
grantedAuthorities = new GrantedAuthority[roles.size()];
for (int i = 0; i < roles.size(); i++) {
Role role = roles.get(i);
GrantedAuthority authority = new GrantedAuthorityImpl(role.getRoleCode());
grantedAuthorities[i] = authority;
}
}
else{
throw new BadCredentialsException("Invalid username/password");
}
return new UsernamePasswordAuthenticationToken(user, authentication.getCredentials(), grantedAuthorities);
}
}
At the client side (jsp), the simple configuration you need to do is post the request to"/j_spring_security_check" with parameters "j_username" and "j_password".
That's pretty much all you need to do for enabling spring security to your existing web application. I will try to explain about doing the method security using ACL's and configuring the view using spring security tags in another post.
作者相信ga版本将会在不久的未来发布。
所作者透露，在新版本中会增加一个新的组件：dynamic.
这个组件的用途是更换皮肤。在旧版本的tapestry中，由于tapestry的模板是一致的，所以要实现换肤相当困难。
但在新版本中的这个组件比较完美地解决了这个问题。
作者自我评价这个组件是令人激动的一个新事物。
现在打开iBatis的主页：ibatis.apache.org会发现作者发布了一个新闻或者说是声明。
大意是因为各种原因，已经把iBatis更名为MyBatis, 并且搬迁到Google Code中了。
新的主页地址是： http://www.mybatis.org
另外，MyBatis3.0.1的正式版已经在http://code.google.com/p/mybatis/可以下载了。
4月17日，iBatis3.0的GA版本的候选版本(candidate)已经在主页上公布出来了（ibatis.apache.org)
根据其描述，只有PMC的投票才会被真正的计算。但是同时又补充说明，其实很多PMC的投票是参考社区用户的投票结果的。
所以也鼓励大家发表自己的看法，并期待大家的反馈。
原文：
After well over a year of development and testing effort, iBATIS 3.0 is now ready for prime time. I've uploaded the new bundles for iBATIS 3 Core and Migrations. It is this release that we'll vote on for GA status. I'll leave the vote open for a good while (maybe a couple of weeks), just to give everyone a chance to try it out. As usual, only PMC votes actually count, but many PMC members will vote based on the community votes. So please offer your feedback. Otherwise, enjoy iBATIS 3.0!
在最上面添加了标签页，目前分了6大块：Java,SOA,.Net,TEST,AJAX,TSSJs
主框架也进行了调整，从原来的2列变成了3列，将原来在右边的要点移到了左边。文章占据了中间最大片的面积。最右边是新闻。
感觉整个界面比原来的色调要清新明亮，版块分割的更清楚。
出自伏尔泰的名句。在许多优秀的程序员的编程习惯中，寻找解决方案就如同是寻找女友一般，总是力求完美，如果一个解决方案不够完美的话，那么宁可舍弃也不会降低标准而采用。但是这样的结果很有可能会是一叶障目，不见森林。
举个实际的例子来说，tapestry5的服务动态加载就是一个典型。
大家知道，在Tapestry中，页面模板的动态加载一直是其的一个宣传点。也就是说，页面模板如果修改了，不需要重新启动应用服务器，修改即时生效。但是，Tapestry却一直没有实现服务的动态加载，也就是说服务的类修改了，就必须重新启动服务器。为什么呢，因为追求完美。
其实很久以前在Tapestry的作者的头脑中，包括许多的用户都想在Tapestry中加入服务动态加载的功能，但是最后作者却放弃了。原因是因为，在Tapestry的架构中，服务比页面要复杂的多，服务不是单独存在的，他会被Inject到许多其他的服务，而这些服务又会被inject到其他的服务中，最后导致你很难界定哪些类需要被重新加载。
但是最近有一个人提出一个建议，为什么要实现完整的动态加载呢。其实只实现服务的实现类的动态加载就已经很好了。
确实，如果保持接口不变，只在接口具体实现修改的时候加载，确实大大简化了问题，因为这样变化范围就被限定在单个类之内了。虽然这样并不完美，因为如果改变了对外接口，比如，添加了一个新的方法，或者改变了方法的签名，还是需要重新启动服务器。可是这样也已经在很大程度上提升了用户的使用满意度。
正如有句古语所说：退一步海阔天空。也在此提醒自己在以后的开发过程中，尽量拓展自己的思维，不要一下子钻到牛角尖里。
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