001/** 002 * Logback: the reliable, generic, fast and flexible logging framework. 003 * Copyright (C) 1999-2015, QOS.ch. All rights reserved. 004 * 005 * This program and the accompanying materials are dual-licensed under 006 * either the terms of the Eclipse Public License v1.0 as published by 007 * the Eclipse Foundation 008 * 009 * or (per the licensee's choosing) 010 * 011 * under the terms of the GNU Lesser General Public License version 2.1 012 * as published by the Free Software Foundation. 013 */ 014package ch.qos.logback.core.pattern; 015 016/** 017 * A minimal converter which sets up the general interface for derived classes. 018 * It also implements the functionality to chain converters in a linked list. 019 * 020 * @author ceki 021 */ 022abstract public class Converter<E> { 023 024 Converter<E> next; 025 026 /** 027 * The convert method is responsible for extracting data from the event and 028 * storing it for later use by the write method. 029 * 030 * @param event 031 */ 032 public abstract String convert(E event); 033 034 /** 035 * In its simplest incarnation, a convert simply appends the data extracted from 036 * the event to the buffer passed as parameter. 037 * 038 * @param buf The input buffer where data is appended 039 * @param event The event from where data is extracted 040 */ 041 public void write(StringBuilder buf, E event) { 042 buf.append(convert(event)); 043 } 044 045 public final void setNext(Converter<E> next) { 046 if (this.next != null) { 047 throw new IllegalStateException("Next converter has been already set"); 048 } 049 this.next = next; 050 } 051 052 public final Converter<E> getNext() { 053 return next; 054 } 055}