Logger (FreeMarker 2.3.23 API)

java.lang.Object
- freemarker.log.Logger

```
public abstract class Logger
extends Object
```
Delegates logger creation to an actual logging library. By default it looks for logger libraries in this order (in FreeMarker 2.3.x): Log4J, Avalon LogKit, JUL (i.e., java.util.logging). Prior to FreeMarker 2.4, SLF4J and Apache Commons Logging aren't searched automatically due to backward compatibility constraints. But if you have log4j-over-slf4j properly installed (means, you have no real Log4j in your class path, and SLF4J has a backing implementation like logback-classic), then FreeMarker will use SLF4J directly instead of Log4j (since FreeMarker 2.3.22).
If the auto detection sequence describet above doesn't give you the result that you want, see SYSTEM_PROPERTY_NAME_LOGGER_LIBRARY.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`LIBRARY_AUTO` Enum value used for `selectLoggerLibrary(int)`; indicates auto-selection as described in the class documentation of `Logger()`.
`static int`	`LIBRARY_AVALON` Deprecated. Avalon LogKit support will be removed sometimes in the future.
`static int`	`LIBRARY_COMMONS` Enum value used for `selectLoggerLibrary(int)`; indicates that Apache commons-logging should be used.
`static int`	`LIBRARY_JAVA` Enum value used for `selectLoggerLibrary(int)`; indicates that `java.util.logging` should be used.
`static int`	`LIBRARY_LOG4J` Enum value used for `selectLoggerLibrary(int)`; indicates that Log4J should be used.
`static String`	`LIBRARY_NAME_AUTO` "org.freemarker.loggerLibrary" property value; indicates auto-selection as described in the class documentation of `Logger()`.
`static String`	`LIBRARY_NAME_AVALON` Deprecated. Avalon LogKit support will be removed sometimes in the future.
`static String`	`LIBRARY_NAME_COMMONS_LOGGING` "org.freemarker.loggerLibrary" property value; indicates that Apache commons-logging should be used.
`static String`	`LIBRARY_NAME_JUL` "org.freemarker.loggerLibrary" property value; indicates that `java.util.logging` should be used.
`static String`	`LIBRARY_NAME_LOG4J` "org.freemarker.loggerLibrary" property value; indicates that Log4J should be used.
`static String`	`LIBRARY_NAME_NONE` "org.freemarker.loggerLibrary" property value; indicates that no logging should occur.
`static String`	`LIBRARY_NAME_SLF4J` "org.freemarker.loggerLibrary" property value; indicates that SLF4J should be used.
`static int`	`LIBRARY_NONE` Enum value used for `selectLoggerLibrary(int)`; indicates that no logging should occur.
`static int`	`LIBRARY_SLF4J` Constant used with `selectLoggerLibrary(int)`; indicates that SLF4J should be used.
`static String`	`SYSTEM_PROPERTY_NAME_LOGGER_LIBRARY` The "org.freemarker.loggerLibrary" system property is used to select a logger library explicitly, rather than relying on automatic selection.

Constructor Summary

Constructors
Constructor and Description

Logger()

Constructors
Constructor and Description
`Logger()`

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`abstract void`	`debug(String message)` Logs a debugging message.
`abstract void`	`debug(String message, Throwable t)` Logs a debugging message with accompanying throwable.
`abstract void`	`error(String message)` Logs an error message.
`abstract void`	`error(String message, Throwable t)` Logs an error message with accompanying throwable.
`static Logger`	`getLogger(String category)` Returns a logger for the specified category.
`abstract void`	`info(String message)` Logs an informational message.
`abstract void`	`info(String message, Throwable t)` Logs an informational message with accompanying throwable.
`abstract boolean`	`isDebugEnabled()` Returns true if this logger will log debug messages.
`abstract boolean`	`isErrorEnabled()` Returns true if this logger will log error messages.
`abstract boolean`	`isFatalEnabled()` Returns true if this logger will log fatal error messages.
`abstract boolean`	`isInfoEnabled()` Returns true if this logger will log informational messages.
`abstract boolean`	`isWarnEnabled()` Returns true if this logger will log warning messages.
`static void`	`selectLoggerLibrary(int libraryEnum)` Deprecated. This method isn't reliable, unless you can somehow ensure that you access the FreeMarker classes first; use the "org.freemarker.loggerLibrary" Java system property instead, like `java ... -Dorg.freemarker.loggerLibrary=slf4j`. See `SYSTEM_PROPERTY_NAME_LOGGER_LIBRARY` for more.
`static void`	`setCategoryPrefix(String prefix)` Deprecated. This wasn't reliable, unless you can somehow ensure that you access the FreeMarker classes first. As it's not known to be useful for users, consider it removed.
`abstract void`	`warn(String message)` Logs a warning message.
`abstract void`	`warn(String message, Throwable t)` Logs a warning message with accompanying throwable.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - SYSTEM_PROPERTY_NAME_LOGGER_LIBRARY
```
public static final String SYSTEM_PROPERTY_NAME_LOGGER_LIBRARY
```
    The "org.freemarker.loggerLibrary" system property is used to select a logger library explicitly, rather than relying on automatic selection. You meant to set this system property where the JVM is started, like java ... -Dorg.freemarker.loggerLibrary=SLF4j. Setting it from Java code isn't reliable, also it can cause confusion if you override the value set by others with -D.
    If the requested logging library is not available, an error will be printed to the stderr, then logging will be disabled.
    The supported values are:
    - "SLF4J": Use SLF4J (recommended)
    - "CommonsLogging": Use Apache Commons Logging.
    - "Log4j": Use Log4j.
    - "JUL": Use java.util.logging.
    - "Avalon": Use Avalon LogKit (deprecated)
    - "auto": Use automatic selection (default behavior). See Logger class documentation for more.
    - "none": Don't log.
    Since:
    
    2.3.22
    
    See Also:
    
    Constant Field Values
  - LIBRARY_AUTO
```
public static final int LIBRARY_AUTO
```
    Enum value used for selectLoggerLibrary(int); indicates auto-selection as described in the class documentation of Logger().
    
    See Also:
    
    Constant Field Values
  - LIBRARY_NAME_AUTO
```
public static final String LIBRARY_NAME_AUTO
```
    "org.freemarker.loggerLibrary" property value; indicates auto-selection as described in the class documentation of Logger(). @since 2.3.22
    
    See Also:
    
    Constant Field Values
  - LIBRARY_NONE
```
public static final int LIBRARY_NONE
```
    Enum value used for selectLoggerLibrary(int); indicates that no logging should occur.
    
    See Also:
    
    Constant Field Values
  - LIBRARY_NAME_NONE
```
public static final String LIBRARY_NAME_NONE
```
    "org.freemarker.loggerLibrary" property value; indicates that no logging should occur. @since 2.3.22
    
    See Also:
    
    Constant Field Values
  - LIBRARY_JAVA
```
public static final int LIBRARY_JAVA
```
    Enum value used for selectLoggerLibrary(int); indicates that java.util.logging should be used.
    
    See Also:
    
    Constant Field Values
  - LIBRARY_NAME_JUL
```
public static final String LIBRARY_NAME_JUL
```
    "org.freemarker.loggerLibrary" property value; indicates that java.util.logging should be used. @since 2.3.22
    
    See Also:
    
    Constant Field Values
  - LIBRARY_AVALON
```
public static final int LIBRARY_AVALON
```
    Deprecated. Avalon LogKit support will be removed sometimes in the future.
    
    Enum value used for selectLoggerLibrary(int); indicates that Avalon LogKit should be used.
    
    See Also:
    
    Constant Field Values
  - LIBRARY_NAME_AVALON
```
public static final String LIBRARY_NAME_AVALON
```
    Deprecated. Avalon LogKit support will be removed sometimes in the future.
    
    "org.freemarker.loggerLibrary" property value; indicates that Avalon LogKit should be used. @since 2.3.22
    
    See Also:
    
    Constant Field Values
  - LIBRARY_LOG4J
```
public static final int LIBRARY_LOG4J
```
    Enum value used for selectLoggerLibrary(int); indicates that Log4J should be used.
    
    See Also:
    
    Constant Field Values
  - LIBRARY_NAME_LOG4J
```
public static final String LIBRARY_NAME_LOG4J
```
    "org.freemarker.loggerLibrary" property value; indicates that Log4J should be used. @since 2.3.22
    
    See Also:
    
    Constant Field Values
  - LIBRARY_COMMONS
```
public static final int LIBRARY_COMMONS
```
    Enum value used for selectLoggerLibrary(int); indicates that Apache commons-logging should be used.
    
    See Also:
    
    Constant Field Values
  - LIBRARY_NAME_COMMONS_LOGGING
```
public static final String LIBRARY_NAME_COMMONS_LOGGING
```
    "org.freemarker.loggerLibrary" property value; indicates that Apache commons-logging should be used. @since 2.3.22
    
    See Also:
    
    Constant Field Values
  - LIBRARY_SLF4J
```
public static final int LIBRARY_SLF4J
```
    Constant used with selectLoggerLibrary(int); indicates that SLF4J should be used.
    
    See Also:
    
    Constant Field Values
  - LIBRARY_NAME_SLF4J
```
public static final String LIBRARY_NAME_SLF4J
```
    "org.freemarker.loggerLibrary" property value; indicates that SLF4J should be used. @since 2.3.22
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - Logger
```
public Logger()
```
- Method Detail
  - selectLoggerLibrary
```
public static void selectLoggerLibrary(int libraryEnum)
                                throws ClassNotFoundException
```
    Deprecated. This method isn't reliable, unless you can somehow ensure that you access the FreeMarker classes first; use the "org.freemarker.loggerLibrary" Java system property instead, like java ... -Dorg.freemarker.loggerLibrary=slf4j. See SYSTEM_PROPERTY_NAME_LOGGER_LIBRARY for more.
    
    Selects the logger library to use, unless it's already specified by the "org.freemarker.loggerLibrary" system property. Call this early in application initialization phase, before calling any other FreeMarker API-s, since once parts of the FreeMarker library bind to the logging subsystem, the change in this value will have no effect on them.
    
    Parameters:
    
    libraryEnum - One of LIBRARY_... constants. By default, LIBRARY_AUTO is used.
    
    Throws:
    
    ClassNotFoundException - if an explicit logging library is asked for (that is, not -1 or 0) and it's not found in the classpath.
  - setCategoryPrefix
```
public static void setCategoryPrefix(String prefix)
```
    Deprecated. This wasn't reliable, unless you can somehow ensure that you access the FreeMarker classes first. As it's not known to be useful for users, consider it removed.
    
    Sets a category prefix. This prefix is prepended to any logger category name. This makes it possible to have different FreeMarker logger categories on a per-application basis (better said, per-classloader basis). By default the category prefix is the empty string. If you set a non-empty category prefix, be sure to include the trailing separator dot (i.e. "MyApp.") If you want to change the default setting, do it early in application initialization phase, before calling any other FreeMarker API since once various parts of the FreeMarker library bind to the logging subsystem, the change in this value will have no effect on them.
  - debug
```
public abstract void debug(String message)
```
    Logs a debugging message.
  - debug
```
public abstract void debug(String message,
                           Throwable t)
```
    Logs a debugging message with accompanying throwable.
  - info
```
public abstract void info(String message)
```
    Logs an informational message.
  - info
```
public abstract void info(String message,
                          Throwable t)
```
    Logs an informational message with accompanying throwable.
  - warn
```
public abstract void warn(String message)
```
    Logs a warning message.
  - warn
```
public abstract void warn(String message,
                          Throwable t)
```
    Logs a warning message with accompanying throwable.
  - error
```
public abstract void error(String message)
```
    Logs an error message.
  - error
```
public abstract void error(String message,
                           Throwable t)
```
    Logs an error message with accompanying throwable.
  - isDebugEnabled
```
public abstract boolean isDebugEnabled()
```
    Returns true if this logger will log debug messages.
  - isInfoEnabled
```
public abstract boolean isInfoEnabled()
```
    Returns true if this logger will log informational messages.
  - isWarnEnabled
```
public abstract boolean isWarnEnabled()
```
    Returns true if this logger will log warning messages.
  - isErrorEnabled
```
public abstract boolean isErrorEnabled()
```
    Returns true if this logger will log error messages.
  - isFatalEnabled
```
public abstract boolean isFatalEnabled()
```
    Returns true if this logger will log fatal error messages.
  - getLogger
```
public static Logger getLogger(String category)
```
    Returns a logger for the specified category.
    
    Parameters:
    
    category - a dot separated hierarchical category name. If a category prefix is in effect, it's prepended to the category name.

Class Logger

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

SYSTEM_PROPERTY_NAME_LOGGER_LIBRARY

LIBRARY_AUTO

LIBRARY_NAME_AUTO

LIBRARY_NONE

LIBRARY_NAME_NONE

LIBRARY_JAVA

LIBRARY_NAME_JUL

LIBRARY_AVALON

LIBRARY_NAME_AVALON

LIBRARY_LOG4J

LIBRARY_NAME_LOG4J

LIBRARY_COMMONS

LIBRARY_NAME_COMMONS_LOGGING

LIBRARY_SLF4J

LIBRARY_NAME_SLF4J

Constructor Detail

Logger

Method Detail

selectLoggerLibrary

setCategoryPrefix

debug

debug

info

info

warn

warn

error

error

isDebugEnabled

isInfoEnabled

isWarnEnabled

isErrorEnabled

isFatalEnabled

getLogger