Package uk.ac.starlink.util

Class BeanConfig

  • public class BeanConfig
extends java.lang.Object
    Utility class for configuring dynamically loaded objects.

    The idea is that objects can be configured from user-supplied text strings that configure bean-like properties. For instance an object may be specified on the command line or using a system property with a syntax like: 

        "java.util.Date(year=212,day=1)"
    which would construct a Date object using its no-arg constructor, and then configure the bean-like "year" property by reflectively invoking the setYear and setDay methods of the Date class.

    Where present, a ConfigMethod annotation on the relevant mutator methods is used to provide aliased property names, as well as to improve LoadException error messages when property setting fails.

    The configuration syntax is fairly straightforward; the format is a comma-separated list of name=value settings within a pair of parentheses. Obvious serializations are supported for numeric and boolean values; string values are unquoted; commas may be backslash-escaped; and symbolic values are permitted for Enums and static public members on the value class or created object class.

    Since:
    11 Sep 2020
    Author:
    Mark Taylor
    See Also:
    ConfigMethod

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static class  BeanConfig.Setting
      Represents an object configuration operation.

    • Constructor Summary

      Constructors 
      Constructor Description
      BeanConfig​(java.lang.String baseTxt, java.lang.String configTxt)
      Constructs a BeanConfig with a basic object representation and a string providing configuration information.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      static void applySetting​(java.lang.Object target, BeanConfig.Setting setting)
      Applies a given setting to an object.
      void configBean​(java.lang.Object target)
      Attempts to apply this object's configuration setttings to a supplied target object.
      java.lang.String getBaseText()
      Returns the basic object name for this object.
      java.lang.String getConfigText()
      Returns configuration specification.
      static java.lang.String getMethodUsage​(java.lang.reflect.Method configMethod)
      Returns a usage string corresponding to a given configuration method.
      BeanConfig.Setting[] getSettings()
      Returns the parsed settings for this object, as extracted from the configuration text.
      static void main​(java.lang.String[] args)  
      static BeanConfig parseSpec​(java.lang.String txt)
      Parses an object specification to produce a BeanConfig instance.

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • BeanConfig

        public BeanConfig​(java.lang.String baseTxt,
                  java.lang.String configTxt)
        Constructs a BeanConfig with a basic object representation and a string providing configuration information. The baseTxt could be a classname or something else. The configTxt should normally be of the form name1=value1,name2=value2,...; if other forms are used, a LoadException with a helpful error message will be generated as appropriate by relevant method invocations.
        Parameters:
        baseTxt - basic object name or representation
        configTxt - configuration text, normally as supplied in trailing parenthesis

    • Method Detail

      • getBaseText

        public java.lang.String getBaseText()
        Returns the basic object name for this object. May be a classname or something else. This should not be null.
        Returns:
        basic representation

      • getConfigText

        public java.lang.String getConfigText()
        Returns configuration specification. May be null if there was no trailing parenthesis.
        Returns:
        configuration text, nominally of the form "n1=v1,n2=v2,...",

      • getSettings

        public BeanConfig.Setting[] getSettings()
                                 throws LoadException
        Returns the parsed settings for this object, as extracted from the configuration text. The list may be empty.
        Returns:
        configuration settings
        Throws:
        LoadException - if the config text was badly-formed

      • configBean

        public void configBean​(java.lang.Object target)
                throws LoadException
        Attempts to apply this object's configuration setttings to a supplied target object.
        Parameters:
        target - object to configure
        Throws:
        LoadException - with a helpful error message if the settings don't work

      • parseSpec

        public static BeanConfig parseSpec​(java.lang.String txt)
        Parses an object specification to produce a BeanConfig instance. The specification is of the form base-name(n1=v1,n2=v2,...). If there is no well-formed parenthesised config-string at the end, the returned object has a base-name that is the whole of the input string, and no config text.
        Parameters:
        txt - input text
        Returns:
        BaseConfig object, which may or may not have configuration information

      • applySetting

        public static void applySetting​(java.lang.Object target,
                                BeanConfig.Setting setting)
                         throws java.lang.ReflectiveOperationException
        Applies a given setting to an object.
        Parameters:
        target - object to configure
        setting - setting to apply
        Throws:
        java.lang.RuntimeException - in case of various problems with converting the supplied string to the required type
        java.lang.ReflectiveOperationException - in case of some reflection trouble

      • getMethodUsage

        public static java.lang.String getMethodUsage​(java.lang.reflect.Method configMethod)
        Returns a usage string corresponding to a given configuration method.
        Parameters:
        configMethod - mutator method
        Returns:
        short user-directed usage text

      • main

        public static void main​(java.lang.String[] args)
                 throws java.lang.ReflectiveOperationException,
                        LoadException
        Throws:
        java.lang.ReflectiveOperationException
        LoadException