com.google.gwt.core.client.impl

Class LoadingStrategyBase

java.lang.Object

com.google.gwt.core.client.impl.LoadingStrategyBase

All Implemented Interfaces:

AsyncFragmentLoader.LoadingStrategy

Direct Known Subclasses:

ScriptTagLoadingStrategy, XhrLoadingStrategy

public class LoadingStrategyBase
extends Object
implements AsyncFragmentLoader.LoadingStrategy

Base for a standard loading strategy used in a web browser. Subclasses provide an implementation of DownloadStrategy, thereby controlling how the download of the code will be done, while the base class controls how to interact with the linker, handle download failures, etc. The linker it is used with should provide JavaScript-level functions to indicate how to handle downloading and installing code. Linkers should always provide a function __gwtStartLoadingFragment. This function is called by this class with two arguments: an integer fragment number that needs to be downloaded, and a one-argument loadFinished function. If the load fails, that function should be called with a descriptive exception as the argument. If the load succeeds, that function may also be called, so long as it isn't called until the downloaded code has been installed. If the mechanism for loading the contents of fragments is provided by the linker, the __gwtStartLoadingFragment function should return null or undefined, and the linker should handle installing the code as well. Note that in this case, all the code in this class is pretty much moot. Alternatively, the function can return a URL designating from where the code for the requested fragment can be downloaded. In that case, the linker should also provide a function __gwtInstallCode for actually installing the code once it is downloaded. That function will be passed the loaded code once it has been downloaded.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static interface	LoadingStrategyBase.DownloadStrategy Subclasses will need to implement this and pass it in in the constructor.
protected static class	LoadingStrategyBase.RequestData Since LoadingStrategy must support concurrent requests, we keep most of the relevant info in the RequestData, and pass it around.

Field Summary

Fields

Modifier and Type	Field and Description
static int	MAX_AUTO_RETRY_COUNT The number of times that we will retry a download.

Constructor Summary

Constructors

Constructor and Description
LoadingStrategyBase(LoadingStrategyBase.DownloadStrategy downloadStrategy) Subclasses should create a DownloadStrategy and pass it into this constructor.

Method Summary

Modifier and Type	Method and Description
LoadingStrategyBase.DownloadStrategy	getDownloadStrategy()
protected int	getMaxAutoRetryCount()
protected static void	gwtInstallCode(String text) Call the linker-supplied __gwtInstallCode method.
protected static String	gwtStartLoadingFragment(int fragment, AsyncFragmentLoader.LoadTerminatedHandler loadErrorHandler) Call the linker-supplied __gwtStartLoadingFragment function.
void	startLoadingFragment(int fragment, AsyncFragmentLoader.LoadTerminatedHandler loadErrorHandler)

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, toString

Field Detail

MAX_AUTO_RETRY_COUNT

public static int MAX_AUTO_RETRY_COUNT

The number of times that we will retry a download. Note that if the install fails, we do not retry, since there's no reason to expect a different result.

Constructor Detail

LoadingStrategyBase

public LoadingStrategyBase(LoadingStrategyBase.DownloadStrategy downloadStrategy)

Subclasses should create a DownloadStrategy and pass it into this constructor.

Method Detail

gwtInstallCode

protected static void gwtInstallCode(String text)

Call the linker-supplied __gwtInstallCode method. This method will attempt to install the code, and throw a runtime exception if it fails, which will get caught by the RequestData.tryInstall() function.

gwtStartLoadingFragment

protected static String gwtStartLoadingFragment(int fragment,
                                                AsyncFragmentLoader.LoadTerminatedHandler loadErrorHandler)

Call the linker-supplied __gwtStartLoadingFragment function. It should either start the download and return null or undefined, or it should return a URL that should be downloaded to get the code. If it starts the download itself, it can synchronously load it, e.g. from cache, if that makes sense.

getDownloadStrategy

public LoadingStrategyBase.DownloadStrategy getDownloadStrategy()

startLoadingFragment

public void startLoadingFragment(int fragment,
                                 AsyncFragmentLoader.LoadTerminatedHandler loadErrorHandler)

Specified by:

startLoadingFragment in interface AsyncFragmentLoader.LoadingStrategy

getMaxAutoRetryCount

protected int getMaxAutoRetryCount()