程序包 org.apache.velocity.tools.generic

类 FieldTool

java.lang.Object
org.apache.velocity.tools.generic.SafeConfig
org.apache.velocity.tools.generic.FieldTool
@DefaultKey("field") @ValidScope("application") public class FieldTool extends SafeConfig

This is a simple tools class to allow easy access to static fields in a class, such as string constants from within a template. Velocity will not introspect for class fields (and won't in the future :), but writing setter/getter methods to do this is a pain, so use this if you really have to access fields.

Example uses in a template:

   ## here we access a constant in a class include in the configuration
     $field.COUNTER_NAME

   ## here we dynamically lookup a class' fields to find another constant
     $field.in("org.com.SomeClass").ANOTHER_CONSTANT

   ## here we pass an object instance in (an Integer in this case) and
   ## retrieve a static constant from that instance's class
     $field.in(0).MIN_VALUE

   ## by default, once we've searched a class' fields, those fields stay
   ## available in the tool (change this by storeDynamicLookups="false")
   ## so here we get another constant from the Integer class
     $field.MAX_VALUE

Example tools.xml config:

 <tools>
   <toolbox scope="application">
     <tool class="org.apache.velocity.tools.generic.FieldTool"
              include="org.apache.velocity.runtime.RuntimeConstants,com.org.MyConstants"/>
   </toolbox>
 </tools>

Right now, this tool only gives access to public static fields. It seems that anything else is too dangerous. This is for convenient access to 'constants'. If you have fields that aren't static, handle them by explicitly placing them into the context or writing a getter method.

从以下版本开始:
VelocityTools 2.0
版本:
$Id: FieldTool.java 463298 2006-10-12 16:10:32Z henning $
作者:
Geir Magnusson Jr., Nathan Bubna

  • 字段详细资料

    • INCLUDE_KEY

      public static final String INCLUDE_KEY
      The key used for specifying which classes should be inspected for public static methods to be made available.
      另请参阅:

    • STORE_DYNAMIC_KEY

      public static final String STORE_DYNAMIC_KEY
      The key used for specifying whether or not the tool should store fields in classes dynamically looked up from within a template. The default value is true.
      另请参阅:

    • storage

      protected HashMap storage

    • storeDynamicLookups

      protected boolean storeDynamicLookups

  • 构造器详细资料

    • FieldTool

      public FieldTool()

  • 方法详细资料

    • configure

      protected void configure(ValueParser values)
      从类复制的说明: SafeConfig
      Does the actual configuration. This is protected, so subclasses may share the same ValueParser and call configure at any time, while preventing templates from doing so when configure(Map) is locked.
      覆盖:
      configure 在类中 SafeConfig
      参数:
      values - configuration values

    • get

      public Object get(String name)
      Returns the value for the specified field name as found in the stored Map of field names to values (or placeholders). Returns null if there is no matching field.
      参数:
      name - field name
      返回:
      field value

    • in

      public FieldTool.FieldToolSub in(String classname)
      Returns a FieldTool.FieldToolSub holding a Map of all the public static field names to values (or a placeholder if the value is not final) for the specified class(name). If the Class with the specified name cannot be loaded, this will return null, rather than throw an exception.
      参数:
      classname - target class name
      返回:
      FieldTool.FieldToolSub object
      另请参阅:

    • in

      public FieldTool.FieldToolSub in(Object instance)
      Returns a FieldTool.FieldToolSub holding a Map of all the public static field names to values (or a placeholder if the value is not final) for the Class of the specified Object.
      参数:
      instance - target instance
      返回:
      FieldTool.FieldToolSub object
      另请参阅:

    • in

      public FieldTool.FieldToolSub in(Class clazz)
      Returns a FieldTool.FieldToolSub holding a Map of all the public static field names to values (or a placeholder if the value is not final) for the specified Class.
      参数:
      clazz - target class
      返回:
      FieldTool.FieldToolSub object

    • inspect

      protected Map<String,Object> inspect(Class clazz)
      Looks for all public, static fields in the specified class and stores their value (if final) or else a FieldTool.MutableField for in a Map under the fields' names. This will never return null, only an empty Map if there are no public static fields.
      参数:
      clazz - target class
      返回:
      fields map

    • retrieve

      protected Object retrieve(Field field, Class clazz)
      Retrieves and returns the value of the specified Field in the specified Class. Returns null in case of failure.
      参数:
      field - target field
      clazz - target class
      返回:
      field value