org.yarnandtail.andhow.load.std

Class StdMainStringArgsLoader

java.lang.Object

org.yarnandtail.andhow.load.BaseLoader

org.yarnandtail.andhow.load.BaseKeyValuePairLoader

org.yarnandtail.andhow.load.std.StdMainStringArgsLoader

All Implemented Interfaces:

Loader, ReadLoader, StandardLoader

public class StdMainStringArgsLoader
extends BaseKeyValuePairLoader
implements StandardLoader

Reads an array of Strings containing key value pairs in the form key=value, and loads the value for any key that matches a Property. This is normally used to read in command line arguments.

Position in Standard Loading Order, first to last

• StdFixedValueLoader
• StdMainStringArgsLoader <-- This loader
• StdSysPropLoader
• StdEnvVarLoader
• StdJndiLoader
• StdPropFileOnFilesystemLoader
• StdPropFileOnClasspathLoader

Property value loading is based on a 'first win' strategy, so the first loader to find a value for a property sets the value.

Typical Use Case

An executable jar or desktop application accepts command line arguments at startup to configure the application. This loader loads the String[] args passed to the main(String[] args), which Java passes from the command line. This is the most common usage, however, your application may retrieve an array of String's from anywhere to pass to AndHow at startup.

Basic Behaviors

• Pre-trims String values: Yes
• Complains about unrecognized properties: No
• Default behavior: None - This loader is only active if command line arguments are passed in as shown below

Loader Details and Configuration

AndHow is not 'there' to somehow intercept command line arguments - Your application code will need to do that and pass those arguments to AndHow, like this:

 import org.yarnandtail.andhow.*;
 
 public class MyAppClass {
   public static void main(String[] args) {
     AndHow.findConfig()
       .setCmdLineArgs(args)
       .build();
   }
 }
 

Passing values from the command line looks like this:

 java -jar MyJarName.jar full.name.of.MY_PROPERTY=someValue

Here is a complete example of using command line arguments.

This is a Standard Loader

Like all StandardLoader's, this loader is intended to be auto-created by AndHow. The set of standard loaders and their order can bet set via the AndHowConfiguration.setStandardLoaders() methods. Other loaders which don't implement the StandardLoader interface can be inserted into the load order via the AndHowConfiguration.insertLoaderBefore/After().

Field Summary

Fields inherited from class org.yarnandtail.andhow.load.BaseKeyValuePairLoader

KVP_DELIMITER, unknownPropertyAProblem

Constructor Summary

Constructors

Constructor and Description
StdMainStringArgsLoader() There is no reason to use the constructor in production application code because AndHow creates a single instance on demand at runtime.

Method Summary

Modifier and Type	Method and Description
String	getLoaderDialect() The type dialect of the loader.
String	getSpecificLoadDescription() For this particular load, where was info loaded from? This may vary from run to run based on config params.
boolean	isFlaggable() Returns true if this loader supports FlaggableType's.
LoaderValues	load(PropertyConfigurationInternal runtimeDef, LoaderEnvironment environment, ValidatedValuesWithContext existingValues) Builds up a list of LoaderValues by loading property values from a configuration source.

Methods inherited from class org.yarnandtail.andhow.load.BaseKeyValuePairLoader

getLoaderType, isTrimmingRequiredForStringValues, isUnknownPropertyAProblem, load, setUnknownPropertyAProblem

Methods inherited from class org.yarnandtail.andhow.load.BaseLoader

attemptToAdd, attemptToAdd, attemptToAdd, attemptToAddIfNotDuplicate, createValue, findDuplicateProperty, getClassConfig, getConfigSamplePrinter, getInstanceConfig, mapNametoProperty, releaseResources

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.yarnandtail.andhow.api.Loader

getClassConfig, getConfigSamplePrinter, getInstanceConfig, getLoaderType, isTrimmingRequiredForStringValues, releaseResources

Constructor Detail

StdMainStringArgsLoader

public StdMainStringArgsLoader()

There is no reason to use the constructor in production application code because AndHow creates a single instance on demand at runtime.

Method Detail

load

public LoaderValues load(PropertyConfigurationInternal runtimeDef,
                         LoaderEnvironment environment,
                         ValidatedValuesWithContext existingValues)

Description copied from interface: Loader

Builds up a list of LoaderValues by loading property values from a configuration source.

Loaders find and load values and associate them with the correct Property. If there is a problem while doing that, they register one or more LoaderProblems in the returned LoaderValues.

Validation of Property values is not Loader's responsibility and will be handled outside this method.

Specified by:

load in interface Loader

Parameters:

runtimeDef - The definition of all known Properties and naming metadata.

environment - The environment (System Props, Env vars, fixed values) as known to the Loader.

existingValues - The values already set by prior loaders, which may configure the behavior of this loader.

Returns:

The Property values loaded by this loader and/or the problems discovered while attempting to load those Property values.

getSpecificLoadDescription

public String getSpecificLoadDescription()

Description copied from interface: Loader

For this particular load, where was info loaded from? This may vary from run to run based on config params. For instance, The PropFileLoader will look multiple places to find a properties file. This method should return the actual location it was found. Assume the text is prefixed with "This loader loaded from: ". An example would be "/home/user/config/my-props.properties" No ending punctuation should be used.

Specified by:

getSpecificLoadDescription in interface Loader

Overrides:

getSpecificLoadDescription in class BaseKeyValuePairLoader

Returns:

getLoaderDialect

public String getLoaderDialect()

Description copied from interface: Loader

The type dialect of the loader. For property files, this might be either KeyValuePair or xml for example. The actual return value is arbitrary, but should be consistent between loaders of the same type and dialect. The values returned by getLoaderType and getLoaderDialect are used to removed duplicate loader types when printing sample files. If two loader instances are of the same type and dialect, only one will print the sample file.

Specified by:

getLoaderDialect in interface Loader

Overrides:

getLoaderDialect in class BaseKeyValuePairLoader

Returns:

May return null if there is no meaningful dialect for this type.

isFlaggable

public boolean isFlaggable()

Description copied from interface: Loader

Returns true if this loader supports FlaggableType's.

Loaders that support FlaggableType give special 'is present' meaning to a property being present without a value, similar to a 'nix command line flag. If a Loader supports flags, it should call FlaggableType.parseFlag(String) instead of ValueType.parse(String) when a Property's ValueType is a FlaggableType. See FlagProp for an example type.

Note: Returning true from this method is only potentially applicable to Loaders that parse strings. Loaders that directly load from rich values do not parse, so the loader logic would ignore the value here.

Examples:
Loading a non-null value from the properties file entry 'name = ' would be unexpected, so a properties file Loader should return 'false' here.
However, a command line loader would be expected to support flags, so should return 'true'.

Specified by:

isFlaggable in interface Loader

Overrides:

isFlaggable in class BaseKeyValuePairLoader

Returns:

true if this loader support 'nix style flag semantics for FlaggableType Properties.