scriptella.core.EtlVariable Maven / Gradle / Ivy
/*
* Copyright 2006-2012 The Scriptella Project Team.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package scriptella.core;
import scriptella.spi.ParametersCallback;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Map;
/**
* Represents a global etl variable available for all ETL file elements.
* As of 1.1 a new syntax is introduced based on
* JEXL function namespaces:
*
* date: namespace contains functions from
* {@link EtlVariable.DateUtils}, e.g. date:now()text: namespace contains functions from
* {@link EtlVariable.TextUtils}, e.g. text:ifNull()class: namespace contains functions from
* {@link EtlVariable.ClassUtils},
* e.g. class:forName('java.lang.System').getProperty('java.version')
*
* @author Fyodor Kupolov
* @version 1.0
*/
public class EtlVariable implements ParametersCallback {
public static final String NAME = "etl";
private final DateUtils date = new DateUtils();
private final TextUtils text = new TextUtils();
private final ClassUtils clazz = new ClassUtils();
private ParametersCallback parametersCallback;
private Map globals;
public EtlVariable(ParametersCallback parametersCallback, Map globals) {
this.parametersCallback = parametersCallback;
this.globals = globals;
}
public EtlVariable() {
}
public DateUtils getDate() {
return date;
}
public TextUtils getText() {
return text;
}
public ClassUtils getClazz() {
return clazz;
}
public Class loadClass(String name) throws ClassNotFoundException {
return Class.forName(name);
}
/**
* Accessor method for parameters available in the current execution context.
* Useful for cases when variables has special symbols which cannot be referenced as normal JEXL variables, e.g.
* etl.getParameter('Column Name')
*
* @param name parameter name.
* @return value of the parameter.
*/
public Object getParameter(String name) {
return parametersCallback.getParameter(name);
}
/**
* Getter for a global variables storage.
* This map is shared between all etl file elements and can be used for cases when there is a need to share some state globally.
* It is recommended to avoid using global variables except cases when it's really beneficiary and simplifies the ETL file.
* @return map of global variables in the scope of ETL file.
*/
public Map getGlobals() {
return globals;
}
/**
* Utility class for ETL file expressions.
* Provides format/parse operation for date/time.
*/
public static class DateUtils {
/**
* Returns a current date/time formatted according to the specified format.
*
* @param formatPattern format pattern as specified by {@link java.text.SimpleDateFormat}.
* @return formatted string representation of current date/time.
* @see java.text.SimpleDateFormat
* @see #format(java.util.Date,String)
*/
public String now(String formatPattern) {
return format(now(), formatPattern);
}
/**
* Formats a specified date/time according to the specified pattern.
*
* @param date date to format.
* @param formatPattern format pattern as specified by {@link java.text.SimpleDateFormat}.
* @return formatted string representation of the specified date/time.
*/
public String format(Date date, String formatPattern) {
return new SimpleDateFormat(formatPattern).format(date);
}
public Date parse(String dateStr, String formatPattern) throws ParseException {
return new SimpleDateFormat(formatPattern).parse(dateStr);
}
/**
* Returns the current date.
*
* @return current date/time.
*/
public Date now() {
return new Date();
}
/**
* Returns the formatted representation of current date.
*
Time part is skipped.
*
* @return formatted representation of current date.
*/
public String today() {
return DateFormat.getDateInstance().format(now());
}
/**
* A synonym for {@link #now(String)}.
*
* @param formatPattern format pattern.
* @return formatted date.
*/
public String today(String formatPattern) {
return now(formatPattern);
}
}
/**
* Utility class for ETL file expressions.
*
Provides text operations.
*
Note: As of version 1.1 the same functionality can be achieved by directly
* using JEXL2.0 syntax elements like ternary operators.
*/
public static class TextUtils {
/**
* Substitute an object when a null value is encountered.
*
* @param object object to check.
* @param replacement replacement object.
* @return object or replacement if object==null
*/
public Object ifNull(Object object, Object replacement) {
return object == null ? replacement : object;
}
/**
* Substitute an object with empty string when a null value is encountered.
*
* @param object object to check.
* @return object or empty string if object==null.
*/
public Object ifNull(Object object) {
return object == null ? "" : object;
}
/**
* If expr1 = expr2 is true, return NULL else return expr1.
*
* @param expr1 first expression
* @param expr2 second expression
* @return true if expr1 = expr2, otherwise null.
*/
public Object nullIf(Object expr1, Object expr2) {
if (expr1 == null) {
return null;
} else {
return expr1.equals(expr2) ? null : expr1;
}
}
}
/**
* Utility class for ETL expressions.
*
Provides class utilities.
*/
public static class ClassUtils {
public Class forName(String className) throws ClassNotFoundException {
return Class.forName(className);
}
}
}