Class FieldTool
- java.lang.Object
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- org.apache.velocity.tools.generic.SafeConfig
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- org.apache.velocity.tools.generic.FieldTool
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@DefaultKey("field") 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'tstatic
, handle them by explicitly placing them into the context or writing a getter method.- Since:
- VelocityTools 2.0
- Version:
- $Id: FieldTool.java 463298 2006-10-12 16:10:32Z henning $
- Author:
- Geir Magnusson Jr., Nathan Bubna
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
FieldTool.FieldToolSub
Holds aMap
of results for a particular class.static class
FieldTool.MutableField
Holds aField
andClass
reference for later retrieval of the value of a field that is not final and may change at different lookups.
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Field Summary
Fields Modifier and Type Field Description static java.lang.String
INCLUDE_KEY
The key used for specifying which classes should be inspected for public static methods to be made available.protected org.apache.velocity.runtime.log.Log
log
protected java.util.HashMap
storage
static java.lang.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.protected boolean
storeDynamicLookups
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Fields inherited from class org.apache.velocity.tools.generic.SafeConfig
LOCK_CONFIG_KEY, OLD_LOCK_CONFIG_KEY, SAFE_MODE_KEY
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Constructor Summary
Constructors Constructor Description FieldTool()
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description protected void
configure(ValueParser values)
Does the actual configuration.java.lang.Object
get(java.lang.String name)
Returns the value for the specified field name as found in the storedMap
of field names to values (or placeholders).FieldTool.FieldToolSub
in(java.lang.Class clazz)
Returns aFieldTool.FieldToolSub
holding aMap
of all the public static field names to values (or a placeholder if the value is not final) for the specifiedClass
.FieldTool.FieldToolSub
in(java.lang.Object instance)
Returns aFieldTool.FieldToolSub
holding aMap
of all the public static field names to values (or a placeholder if the value is not final) for theClass
of the specified Object.FieldTool.FieldToolSub
in(java.lang.String classname)
Returns aFieldTool.FieldToolSub
holding aMap
of all the public static field names to values (or a placeholder if the value is not final) for the specified class(name).protected java.util.Map<java.lang.String,java.lang.Object>
inspect(java.lang.Class clazz)
Looks for all public, static fields in the specified class and stores their value (if final) or else aFieldTool.MutableField
for in aMap
under the fields' names.protected static java.lang.Object
retrieve(java.lang.reflect.Field field, java.lang.Class clazz, org.apache.velocity.runtime.log.Log log)
Retrieves and returns the value of the specifiedField
in the specifiedClass
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Methods inherited from class org.apache.velocity.tools.generic.SafeConfig
configure, isConfigLocked, isSafeMode, setLockConfig, setSafeMode
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Field Detail
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INCLUDE_KEY
public static final java.lang.String INCLUDE_KEY
The key used for specifying which classes should be inspected for public static methods to be made available.- See Also:
- Constant Field Values
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STORE_DYNAMIC_KEY
public static final java.lang.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.- See Also:
- Constant Field Values
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log
protected org.apache.velocity.runtime.log.Log log
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storage
protected java.util.HashMap storage
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storeDynamicLookups
protected boolean storeDynamicLookups
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Method Detail
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configure
protected void configure(ValueParser values)
Description copied from class: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.- Overrides:
configure
in classSafeConfig
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get
public java.lang.Object get(java.lang.String name)
Returns the value for the specified field name as found in the storedMap
of field names to values (or placeholders). Returnsnull
if there is no matching field.
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in
public FieldTool.FieldToolSub in(java.lang.String classname)
Returns aFieldTool.FieldToolSub
holding aMap
of all the public static field names to values (or a placeholder if the value is not final) for the specified class(name). If theClass
with the specified name cannot be loaded, this will returnnull
, rather than throw an exception.- See Also:
in(Class clazz)
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in
public FieldTool.FieldToolSub in(java.lang.Object instance)
Returns aFieldTool.FieldToolSub
holding aMap
of all the public static field names to values (or a placeholder if the value is not final) for theClass
of the specified Object.- See Also:
in(Class clazz)
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in
public FieldTool.FieldToolSub in(java.lang.Class clazz)
Returns aFieldTool.FieldToolSub
holding aMap
of all the public static field names to values (or a placeholder if the value is not final) for the specifiedClass
.
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inspect
protected java.util.Map<java.lang.String,java.lang.Object> inspect(java.lang.Class clazz)
Looks for all public, static fields in the specified class and stores their value (if final) or else aFieldTool.MutableField
for in aMap
under the fields' names. This will never return null, only an empty Map if there are no public static fields.
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retrieve
protected static java.lang.Object retrieve(java.lang.reflect.Field field, java.lang.Class clazz, org.apache.velocity.runtime.log.Log log)
Retrieves and returns the value of the specifiedField
in the specifiedClass
. IfLog
is provided, then access errors will be logged, otherwise this will fail silently and returnnull
.
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