java pdf page break

java pdf page break

java pdf page break

We have seen that HTTP requests and responses are each represented by ad-hoc objects in urllib2. Many Python programmers find its interface unwieldy, as well as incomplete! But, in their defense, the objects seem to have been created as minimal constructs, containing only what urllib2 needed to function. But a library called WebOb is also available for Python (and listed on the Python Package Index) that contains HTTP request and response classes that were designed from the other direction: that is, they were intended all along as general-purpose representations of HTTP in all of its low-level details. You can learn more about them at the WebOb project web page: http://pythonpaste.org/webob/ This library s objects are specifically designed to interface well with WSGI, which makes them useful when writing HTTP servers, as we will see in 11.

Ripping code using the Block Creator is how I got the code for the RSS block for 7, and it s a great way to get started on your own block and learn by examining code from other authors. In this case, learning from the Popfly team at Microsoft can shorten your development time and reduce your learning curve. Click the Block Code tab to see the source code (see Figure 10-4) Again, the RSS block code is the same RSS code we examined in 7. Both the Block Code and Block Description editors are very basic and don t compare to the robust environment of VWD. However, the Block Code editor does have some of the functionality you would expect from an advanced environment, such as a limited code-completion functionality that helps you complete your code and use Popfly s built-in helper objects and other utility functions. Place the cursor in a location in the editor, and begin typing a letter. A drop-down menu should appear below where you are typing (see Figure 10-5).

There are several common hurdles when working with processes. The first one occurs because the command-line shell processes the arguments before passing them on to the executable. For example, writing uic *.ui in a Unix shell will give all file names matching *.ui as arguments to uic. When starting the process using QProcess, you must take care of it and find the actual file names (use a QDir object). The second issue is closely related to the first one. Pipes are managed by the commandline shell. The command ls l | grep foo does mean that the shell passes -l | grep foo as arguments to ls, but that is what happens if you start using QProcess. Instead, you have to run ls l as one process and pass the resulting data to another process running grep foo. This brings you to the last hurdle: the directions of channels. The standard output of a process is your input. What the process writes is what your application reads. This goes for the standard error channel, too the process writes to it so your application reads from it. The standard input is the other way around the process reads from it so your application must write to it.

Summary

Summary

The HTTP protocol sounds simple enough: each request names a document (which can be an image or program or whatever), and responses are supposed to supply its content. But the reality, of course, is rather more complicated, as its main features to support the modern Web have driven its specification, RFC 2616, to nearly 60,000 words. In this chapter, we tried to capture its essence in around 10,000 words and obviously had to leave things out. Along the way, we discussed (and showed sample Python code) for the following concepts:

Using threading increases the complexity of your application, but offers performance gains. This is especially important as multiprocessor systems become more and more common. When developing multithreaded applications, you must make sure to not make any assumptions about timing or performance. You can never rely on things occurring in a certain order or at a certain pace. If you are aware of this, it is really easy to get started just inherit the QThread class and implement the run method. Shared resources are easily protected using the QMutex and QMutexLocker classes. If you mostly read from a value, a better choice is the QReadWriteLock combined with QReadLocker and QWriteLocker for better performance. For shared resources that you use in greater numbers than one, the QSemphore is your best choice.

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