终于遇到第一块硬骨头
Hadoop没有使用java.util.PRoperties管理配置文件，而是自己定义了一套配置文件管理系统和自己的API。
1 package org.apache.hadoop.conf; 2 3 import java.io.BufferedInputStream; 4 import java.io.DataInput; 5 import java.io.DataOutput; 6 import java.io.File; 7 import java.io.FileInputStream; 8 import java.io.IOException; 9 import java.io.InputStream; 10 import java.io.InputStreamReader; 11 import java.io.OutputStream; 12 import java.io.Reader; 13 import java.io.Writer; 14 import java.net.URL; 15 import java.util.ArrayList; 16 import java.util.Collection; 17 import java.util.Enumeration; 18 import java.util.HashMap; 19 import java.util.HashSet; 20 import java.util.Iterator; 21 import java.util.List; 22 import java.util.ListIterator; 23 import java.util.Map; 24 import java.util.Properties; 25 import java.util.Set; 26 import java.util.StringTokenizer; 27 import java.util.WeakHashMap; 28 import java.util.concurrent.CopyOnWriteArrayList; 29 import java.util.regex.Matcher; 30 import java.util.regex.Pattern; 31 //引入了IO的流类 32 //引入了网络编程类，用来封装或获取网络资源 33 //引入了工具包中的集合类。其中StringTokenier在hadoop中用的非常多，特别是在mapreduce编程中，经常需要这个工具类来处理数据。 34 //它起着分词器的作用。 35 //关于CopyOnWriteArrayList，之前没接触过，具体推荐 http://blog.csdn.net/imzoer/article/details/9751591，就是实现了线程安全 36 //关于regex.Matcher和regex.Pattern，看regex可知就是正则类，具体用法不太一样 http://ningtukun.blog.163.com/blog/static/186541445201292984311656/ 37 import javax.xml.parsers.DocumentBuilder; 38 import javax.xml.parsers.DocumentBuilderFactory; 39 import javax.xml.parsers.ParserConfigurationException; 40 import javax.xml.transform.Transformer; 41 import javax.xml.transform.TransformerFactory; 42 import javax.xml.transform.dom.DOMSource; 43 import javax.xml.transform.stream.StreamResult; 44 45 import org.apache.commons.logging.Log; 46 import org.apache.commons.logging.LogFactory; 47 import org.apache.hadoop.fs.FileSystem; 48 import org.apache.hadoop.fs.Path; 49 import org.apache.hadoop.io.Writable; 50 import org.apache.hadoop.io.WritableUtils; 51 import org.apache.hadoop.util.StringUtils; 52 import org.codehaus.jackson.JsonFactory; 53 import org.codehaus.jackson.JsonGenerator; 54 import org.w3c.dom.DOMException; 55 import org.w3c.dom.Document; 56 import org.w3c.dom.Element; 57 import org.w3c.dom.Node; 58 import org.w3c.dom.NodeList; 59 import org.w3c.dom.Text; 60 import org.xml.sax.SAXException; 61 62 /** 63 * Provides access to configuration parameters. 64 * 65 * <h4 id="Resources">Resources</h4> 66 * 67 * <p>Configurations are specified by resources. A resource contains a set of 68 * name/value pairs as XML data. Each resource is named by either a 69 * <code>String</code> or by a {@link Path}. If named by a <code>String</code>, 70 * then the classpath is examined for a file with that name. If named by a 71 * <code>Path</code>, then the local filesystem is examined directly, without 72 * referring to the classpath. 73 * 74 * <p>Unless explicitly turned off, Hadoop by default specifies two 75 * resources, loaded in-order from the classpath: <ol> 76 * <li><tt><a href="{@docRoot}/../core-default.html">core-default.xml</a> 77 * </tt>: Read-only defaults for hadoop.</li> 78 * <li><tt>core-site.xml</tt>: Site-specific configuration for a given hadoop 79 * installation.</li> 80 * </ol> 81 * applications may add additional resources, which are loaded 82 * subsequent to these resources in the order they are added. 83 * 84 * <h4 id="FinalParams">Final Parameters</h4> 85 * 86 * <p>Configuration parameters may be declared <i>final</i>. 87 * Once a resource declares a value final, no subsequently-loaded 88 * resource can alter that value. 89 * For example, one might define a final parameter with: 90 * <tt><pre> 91 * <property> 92 * <name>dfs.client.buffer.dir</name> 93 * <value>/tmp/hadoop/dfs/client</value> 94 * <b><final>true</final></b> 95 * </property></pre></tt> 96 * 97 * Administrators typically define parameters as final in 98 * <tt>core-site.xml</tt> for values that user applications may not alter. 99 * 100 * <h4 id="VariableExpansion">Variable Expansion</h4> 101 * 102 * <p>Value strings are first processed for <i>variable expansion</i>. The 103 * available properties are:<ol> 104 * <li>Other properties defined in this Configuration; and, if a name is 105 * undefined here,</li> 106 * <li>Properties in {@link System#getProperties()}.</li> 107 * </ol> 108 * 109 * <p>For example, if a configuration resource contains the following property 110 * definitions: 111 * <tt><pre> 112 * <property> 113 * <name>basedir</name> 114 * <value>/user/${<i>user.name</i>}</value> 115 * </property> 116 * 117 * <property> 118 * <name>tempdir</name> 119 * <value>${<i>basedir</i>}/tmp</value> 120 * </property></pre></tt> 121 * 122 * When <tt>conf.get("tempdir")</tt> is called, then <tt>${<i>basedir</i>}</tt> 123 * will be resolved to another property in this Configuration, while 124 * <tt>${<i>user.name</i>}</tt> would then ordinarily be resolved to the value 125 * of the System property with that name. 126 */ 127 //一大段注释。第一句说这个类是用来提供访问配置中属性的渠道 128 //第二段话说配置文件的构造，XML文件中键值对。 129 //第三段话说除非主动关闭，否则hadoop会默认加载一些默认的配置文件。并且可以“重载” 130 //第四段说了配置文件中属性标记为final会怎么样 131 //第五段说配置文件中的属性可以用变量来表示，可以不是具体的实值。还举了个例子。 132 public class Configuration implements Iterable<Map.Entry<String,String>>, 133 Writable { 134 //实现了Iterable和Writable接口。 135 //实现Iterable接口，可以调用Iterator()方法进行迭代 136 //关于Map.Entry类，之前不了解。就是map的一种方便的遍历工具类 137 //实现了Writable接口。hadoop没有采用Java的序列化（具体原因不解释），而是引入了自己的序列化系统，所有的 138 //序列化对象都要实现writable接口。以后会遇到。 139 private static final Log LOG = 140 LogFactory.getLog(Configuration.class); 141 //创建了一个日志类。并做了初始化 142 private boolean quietmode = true; 143 //布尔变量quietmode，“安静模式”，用来确定加载配置的时候日志的某些动作， 144 //当为true的时候则在加载解析配置文件的过程中不输出日志信息，反之...... 145 /** 146 * List of configuration resources. 147 */ 148 private ArrayList<Object> resources = new ArrayList<Object>(); 149 //保存了所有通过addResource()方法添加的Configuration对象的资源 150 /** 151 * List of configuration parameters marked <b>final</b>. 152 */ 153 private Set<String> finalParameters = new HashSet<String>(); 154 //用来保存所有在配置文件中已经被声明为final的键–值对的键 155 private boolean loadDefaults = true; 156 //是否加载默认的配置资源 157 /** 158 * Configuration objects 159 */ 160 private static final WeakHashMap<Configuration,Object> REGISTRY = 161 new WeakHashMap<Configuration,Object>(); 162 //REGISTRY是一个WeakHashMap的变量，key为Configuration,value为Object， 163 //可以看出这个对象存储了不同对象的多个配置信息，弱HashMap可以自动清除不在正常使用的键对应的条目， 164 //发现如果这个值是null会重新加载默认的配置文件中的信息 165 /** 166 * List of default Resources. Resources are loaded in the order of the list 167 * entries 168 */ 169 private static final CopyOnWriteArrayList<String> defaultResources = 170 new CopyOnWriteArrayList<String>(); 171 //存放的是默认的配置信息，通过方法addDefaultResource()可以添加系统的默认资源 172 //存储配置文件的名字而不是配置文件的全路径 173 /** 174 * Flag to indicate if the storage of resource which updates a key needs 175 * to be stored for each key 176 */ 177 private boolean storeResource; 178 //是否需要更新配置文件的标识 179 /** 180 * Stores the mapping of key to the resource which modifies or loads 181 * the key most recently 182 */ 183 private HashMap<String, String> updatingResource; 184 //保存所有需要更新的配置文件 185 static{ 186 //print deprecation warning if hadoop-site.xml is found in classpath 187 ClassLoader cL = Thread.currentThread().getContextClassLoader(); 188 if (cL == null) { 189 cL = Configuration.class.getClassLoader(); 190 } 191 if(cL.getResource("hadoop-site.xml")!=null) { 192 LOG.warn("DEPRECATED: hadoop-site.xml found in the classpath. " + 193 "Usage of hadoop-site.xml is deprecated. Instead use core-site.xml, " 194 + "mapred-site.xml and hdfs-site.xml to override properties of " + 195 "core-default.xml, mapred-default.xml and hdfs-default.xml " + 196 "respectively"); 197 } 198 addDefaultResource("core-default.xml"); 199 addDefaultResource("core-site.xml"); 200 } 201 //静态代码块。加载了两个核心配置文件，一个是默认的，一个是用户自己配置的。 202 //如果加载了hadoop-site.xml，则发个警告信息，说它不推荐用，以及推荐用哪个 203 private Properties properties; 204 //Hadoop配置文件解析后的键–值对，都存放在properties中 205 private Properties overlay; 206 //变量overlay用于记录通过set()方式改变的配置项。也就是说，出现在overlay中的键–值对是应用设置的， 207 //而不是通过对配置资源解析得到的 208 private ClassLoader classLoader; 209 { 210 classLoader = Thread.currentThread().getContextClassLoader(); 211 if (classLoader == null) { 212 classLoader = Configuration.class.getClassLoader(); 213 } 214 } 215 //定义了一个类加载器，并做了初始化。非静态代码块 216 /** A new configuration. */ 217 public Configuration() { 218 this(true); 219 } 220 //相当于空构造方法,或者说调用空构造方法的时候默认调用默认配置文件 221 /** A new configuration where the behavior of reading from the default 222 * resources can be turned off. 223 * 224 * If the parameter {@code loadDefaults} is false, the new instance 225 * will not load resources from the default files. 226 * @param loadDefaults specifies whether to load from the default files 227 */ 228 public Configuration(boolean loadDefaults) { 229 this.loadDefaults = loadDefaults; 230 if (LOG.isDebugEnabled()) { 231 LOG.debug(StringUtils.stringifyException(new IOException("config()"))); 232 } 233 synchronized(Configuration.class) { 234 REGISTRY.put(this, null); 235 } 236 this.storeResource = false; 237 } 238 //构造方法。参数是是否加载默认配置文件 239 /** 240 * A new configuration with the same settings and additional facility for 241 * storage of resource to each key which loads or updates 242 * the key most recently 243 * @param other the configuration from which to clone settings 244 * @param storeResource flag to indicate if the storage of resource to 245 * each key is to be stored 246 */ 247 private Configuration(Configuration other, boolean storeResource) { 248 this(other); 249 this.loadDefaults = other.loadDefaults; 250 this.storeResource = storeResource; 251 if (storeResource) { 252 updatingResource = new HashMap<String, String>(); 253 } 254 } 255 //构造方法。加载了一个新的配置文件和现有的配置文件具有相同的一些配置并有一些新的配置 256 /** 257 * A new configuration with the same settings cloned from another. 258 * 259 * @param other the configuration from which to clone settings. 260 */ 261 @SuppressWarnings("unchecked") 262 public Configuration(Configuration other) { 263 if (LOG.isDebugEnabled()) { 264 LOG.debug(StringUtils.stringifyException 265 (new IOException("config(config)"))); 266 } 267 268 this.resources = (ArrayList)other.resources.clone(); 269 synchronized(other) { 270 if (other.properties != null) { 271 this.properties = (Properties)other.properties.clone(); 272 } 273 274 if (other.overlay!=null) { 275 this.overlay = (Properties)other.overlay.clone(); 276 } 277 } 278 279 this.finalParameters = new HashSet<String>(other.finalParameters); 280 synchronized(Configuration.class) { 281 REGISTRY.put(this, null); 282 } 283 } 284 //构造方法。加载了一个全新的配置文件，并克隆了其属性 285 /** 286 * Add a default resource. Resources are loaded in the order of the resources 287 * added. 288 * @param name file name. File should be present in the classpath. 289 */ 290 public static synchronized void addDefaultResource(String name) { 291 if(!defaultResources.contains(name)) { 292 defaultResources.add(name); 293 for(Configuration conf : REGISTRY.keySet()) { 294 if(conf.loadDefaults) { 295 conf.reloadConfiguration(); 296 } 297 } 298 } 299 } 300 //加载默认配置文件方法 301 /** 302 * Add a configuration resource. 303 * 304 * The properties of this resource will override properties of previously 305 * added resources, unless they were marked <a href="#Final">final</a>. 306 * 307 * @param name resource to be added, the classpath is examined for a file 308 * with that name. 309 */ 310 public void addResource(String name) { 311 addResourceObject(name); 312 } 313 314 /** 315 * Add a configuration resource. 316 * 317 * The properties of this resource will override properties of previously 318 * added resources, unless they were marked <a href="#Final">final</a>. 319 * 320 * @param url url of the resource to be added, the local filesystem is 321 * examined directly to find the resource, without referring to 322 * the classpath. 323 */ 324 public void addResource(URL url) { 325 addResourceObject(url); 326 } 327 328 /** 329 * Add a configuration resource. 330 * 331 * The properties of this resource will override properties of previously 332 * added resources, unless they were marked <a href="#Final">final</a>. 333 * 334 * @param file file-path of resource to be added, the local filesystem is 335 * examined directly to find the resource, without referring to 336 * the classpath. 337 */ 338 public void addResource(Path file) { 339 addResourceObject(file); 340 } 341 342 /** 343 * Add a configuration resource. 344 * 345 * The properties of this resource will override properties of previously 346 * added resources, unless they were marked <a href="#Final">final</a>. 347 * 348 * @param in InputStream to deserialize the object from. 349 */ 350 public void addResource(InputStream in) { 351 addResourceObject(in); 352 } 353 //Hadoop在创建配置类的时候，考虑了三种资源： 354 // 355 //URL资源（网络资源，指的是一个链接）； 356 // 357 //CLASSPATH资源（String形式）； 358 // 359 //Hadoop文件系统中的Path资源（该资源是基于Hadoop的FileSystem的，使用斜线“/”作为分隔符，如果是绝对路径，应该以“/”开始） 360 /** 361 * Reload configuration from previously added resources. 362 * 363 * This method will clear all the configuration read from the added 364 * resources, and final parameters. This will make the resources to 365 * be read again before accessing the values. Values that are added 366 * via set methods will overlay values read from the resources. 367 */ 368 public synchronized void reloadConfiguration() { 369 properties = null; // trigger reload 370 finalParameters.clear(); // clear site-limits 371 } 372 //重新加载先前加载过的配置资源。加载前会先清空。加了线程并发关键字哦 373 private synchronized void addResourceObject(Object resource) { 374 resources.add(resource); // add to resources 375 reloadConfiguration(); 376 } 377 //注意resource是Object类型。会触发配置的重新加载 378 private static Pattern varPat = Pattern.compile("//$//{[^//}//$/u0020]+//}"); 379 private static int MAX_SUBST = 20; 380 381 private String substituteVars(String expr) { 382 if (expr == null) { 383 return null; 384 } 385 Matcher match = varPat.matcher(""); 386 String eval = expr; 387 for(int s=0; s<MAX_SUBST; s++) { 388 match.reset(eval); 389 if (!match.find()) { 390 return eval; 391 } 392 String var = match.group(); 393 var = var.substring(2, var.length()-1); // remove ${ .. } 394 String val = null; 395 try { 396 val = System.getProperty(var); 397 } catch(SecurityException se) { 398 LOG.warn("Unexpected SecurityException in Configuration", se); 399 } 400 if (val == null) { 401 val = getRaw(var); 402 } 403 if (val == null) { 404 return eval; // return literal ${var}: var is unbound 405 } 406 // substitute 407 eval = eval.substring(0, match.start())+val+eval.substring(match.end()); 408 } 409 throw new IllegalStateException("Variable substitution depth too large: " 410 + MAX_SUBST + " " + expr); 411 } 412 //属性扩展属性和方法。 413 //varPat对含有环境变量的值的进行转换的正则表达式对象； 414 //MAX_SUBST是循环次数，为了避免死循环； 415 //当循环次数过多的时候抛异常。 416 /** 417 * Get the value of the <code>name</code> property, <code>null</code> if 418 * no such property exists. 419 * 420 * Values are processed for <a href="#VariableExpansion">variable expansion</a> 421 * before being returned. 422 * 423 * @param name the property name. 424 * @return the value of the <code>name</code> property, 425 * or null if no such property exists. 426 */ 427 public String get(String name) { 428 return substituteVars(getProps().getProperty(name)); 429 } 430 431 /** 432 * Get the value of the <code>name</code> property, without doing 433 * <a href="#VariableExpansion">variable expansion</a>. 434 * 435 * @param name the property name. 436 * @return the value of the <code>name</code> property, 437 * or null if no such property exists. 438 */ 439 public String getRaw(String name) { 440 return getProps().getProperty(name); 441 } 442 //两种根据名称取得属性值的方法。没有这个属性就返回NULL。 443 //区别是第一个会进行属性扩展，第二个不会 444 /** 445 * Set the <code>value</code> of the <code>name</code> property. 446 * 447 * @param name property name. 448 * @param value property value. 449 */ 450 public void set(String name, String value) { 451 getOverlay().setProperty(name, value); 452 getProps().setProperty(name, value); 453 } 454 455 /** 456 * Sets a property if it is currently unset. 457 * @param name the property name 458 * @param value the new value 459 */ 460 public void setIfUnset(String name, String value) { 461 if (get(name) == null) { 462 set(name, value); 463 } 464 } 465 //两种根据名称设置值得方法。区别不解释 466 private synchronized Properties getOverlay() { 467 if (overlay==null){ 468 overlay=new Properties(); 469 } 470 return overlay; 471 } 472 473 /** 474 * Get the value of the <code>name</code> property. If no such property 475 * exists, then <code>defaultValue</code> is returned. 476 * 477 * @param name property name. 478 * @param defaultValue default value. 479 * @return property value, or <code>defaultValue</code> if the property 480 * doesn't exist. 481 */ 482 public String get(String name, String defaultValue) { 483 return substituteVars(getProps().getProperty(name, defaultValue)); 484 } 485 486 /** 487 * Get the value of the <code>name</code> property as an <code>int</code>. 488 * 489 * If no such property exists, or if the specified value is not a valid 490 * <code>int</code>, then <code>defaultValue</code> is returned. 491 * 492 * @param name property name. 493 * @param defaultValue default value. 494 * @return property value as an <code>int</code>, 495 * or <code>defaultValue</code>. 496 */ 497 public int getInt(String name, int defaultValue) { 498 String valueString = get(name); 499 if (valueString == null) 500 return defaultValue; 501 try { 502 String hexString = getHexDigits(valueString); 503 if (hexString != null) { 504 return Integer.parseInt(hexString, 16); 505 } 506 return Integer.parseInt(valueString); 507 } catch (NumberFormatException e) { 508 return defaultValue; 509 } 510 } 511 512 /** 513 * Set the value of the <code>name</code> property to an <code>int</code>. 514 * 515 * @param name property name. 516 * @param value <code>int</code> value of the property. 517 */ 518 public void setInt(String name, int value) { 519 set(name, Integer.toString(value)); 520 } 521 522 523 /** 524 * Get the value of the <code>name</code> property as a <code>long</code>. 525 * If no such property is specified, or if the specified value is not a valid 526 * <code>long</code>, then <code>defaultValue</code> is returned. 527 * 528 * @param name property name. 529 * @param defaultValue default value. 530 * @return property value as a <code>long</code>, 531 * or <code>defaultValue</code>. 532 */ 533 public long getLong(String name, long defaultValue) { 534 String valueString = get(name); 535 if (valueString == null) 536 return defaultValue; 537 try { 538 String hexString = getHexDigits(valueString); 539 if (hexString != null) { 540 return Long.parseLong(hexString, 16); 541 } 542 return Long.parseLong(valueString); 543 } catch (NumberFormatException e) { 544 return defaultValue; 545 } 546 } 547 548 private String getHexDigits(String value) { 549 boolean negative = false; 550 String str = value; 551 String hexString = null; 552 if (value.startsWith("-")) { 553 negative = true; 554 str = value.substring(1); 555 } 556 if (str.startsWith("0x") || str.startsWith("0X")) { 557 hexString = str.substring(2); 558 if (negative) { 559 hexString = "-" + hexString; 560 } 561 return hexString; 562 } 563 return null; 564 } 565 566 /** 567 * Set the value of the <code>name</code> property to a <code>long</code>. 568 * 569 * @param name property name. 570 * @param value <code>long</code> value of the property. 571 */ 572 public void setLong(String name, long value) { 573 set(name, Long.toString(value)); 574 } 575 576 /** 577 * Get the value of the <code>name</code> property as a <code>float</code>. 578 * If no such property is specified, or if the specified value is not a valid 579 * <code>float</code>, then <code>defaultValue</code> is returned. 580 * 581 * @param name property name. 582 * @param defaultValue default value. 583 * @return property value as a <code>float</code>, 584 * or <code>defaultValue</code>. 585 */ 586 public float getFloat(String name, float defaultValue) { 587 String valueString = get(name); 588 if (valueString == null) 589 return defaultValue; 590 try { 591 return Float.parseFloat(valueString); 592 } catch (NumberFormatException e) { 593 return defaultValue; 594 } 595 } 596 /** 597 * Set the value of the <code>name</code> property to a <code>float</code>. 598 * 599 * @param name property name. 600 * @param value property value. 601 */ 602 public void setFloat(String name, float value) { 603 set(name,Float.toString(value)); 604 } 605 606 /** 607 * Get the value of the <code>name</code> property as a <code>boolean</code>. 608 * If no such property is specified, or if the specified value is not a valid 609 * <code>boolean</code>, then <code>defaultValue</code> is returned. 610 * 611 * @param name property name. 612 * @param defaultValue default value. 613 * @return property value as a <code>boolean</code>, 614 * or <code>defaultValue</code>. 615 */ 616 public boolean getBoolean(String name, boolean defaultValue) { 617 String valueString = get(name); 618 if ("true".equals(valueString)) 619 return true; 620 else if ("false".equals(valueString)) 621 return false; 622 else return defaultValue; 623 } 624 625 /** 626 * Set the value of the <code>name</code> property to a <code>boolean</code>. 627 * 628 * @param name property name. 629 * @param value <code>boolean</code> value of the property. 630 */ 631 public void setBoolean(String name, boolean value) { 632 set(name, Boolean.toString(value)); 633 } 634 635 /** 636 * Set the given property, if it is currently unset. 637 * @param name property name 638 * @param value new value 639 */ 640 public void setBooleanIfUnset(String name, boolean value) { 641 setIfUnset(name, Boolean.toString(value)); 642 } 643 644 /** 645 * Set the value of the <code>name</code> property to the given type. This 646 * is equivalent to <code>set(<name>, value.toString())</code>. 647 * @param name property name 648 * @param value new value 649 */ 650 public <T extends Enum<T>> void setEnum(String name, T value) { 651 set(name, value.toString()); 652 } 653 654 /** 655 * Return value matching this enumerated type. 656 * @param name Property name 657 * @param defaultValue Value returned if no mapping exists 658 * @throws IllegalArgumentException If mapping is illegal for the type 659 * provided 660 */ 661 public <T extends Enum<T>> T getEnum(String name, T defaultValue) { 662 final String val = get(name); 663 return null == val 664 ? defaultValue 665 : Enum.valueOf(defaultValue.getDeclaringClass(), val); 666 } 667 //hadoop常用类型的get/set方法，其中有的做了转换。 668 /** 669 * A class that represents a set of positive integer ranges. It parses 670 * strings of the form: "2-3,5,7-" where ranges are separated by comma and 671 * the lower/upper bounds are separated by dash. Either the lower or upper 672 * bound may be omitted meaning all values up to or over. So the string 673 * above means 2, 3, 5, and 7, 8, 9, ... 674 */ 675 public static class IntegerRanges { 676 private static class Range { 677 int start; 678 int end; 679 } 680 681 List<Range> ranges = new ArrayList<Range>(); 682 683 public IntegerRanges() { 684 } 685 686 public IntegerRanges(String newValue) { 687 StringTokenizer itr = new StringTokenizer(newValue, ","); 688 while (itr.hasMoreTokens()) { 689 String rng = itr.nextToken().trim(); 690 String[] parts = rng.split("-", 3); 691 if (parts.length < 1 || parts.length > 2) { 692 throw new IllegalArgumentException("integer range badly formed: " + 693 rng); 694 } 695 Range r = new Range(); 696 r.start = convertToInt(parts[0], 0); 697 if (parts.length == 2) { 698 r.end = convertToInt(parts[1], Integer.MAX_VALUE); 699 } else { 700 r.end = r.start; 701 } 702 if (r.start > r.end) { 703 throw new IllegalArgumentException("IntegerRange from " + r.start + 704 " to " + r.end + " is invalid"); 705 } 706 ranges.add(r); 707 } 708 } 709 //嵌套类。所以org.apache.hadoop.conf包中有四个类。 710 //解释一种字符串表示的整数范围。注释中有例子。 711 /** 712 * Convert a string to an int treating empty strings as the default value. 713 * @param value the string value 714 * @param defaultValue the value for if the string is empty 715 * @return the desired integer 716 */ 717 private static int convertToInt(String value, int defaultValue) { 718 String trim = value.trim(); 719 if (trim.length() == 0) { 720 return defaultValue; 721 } 722 return Integer.parseInt(trim); 723 } 724 //字符串转整数方法。如果是空的就是用默认值 725 /** 726 * Is the given value in the set of ranges 727 * @param value the value to check 728 * @return is the value in the ranges? 729 */ 730 public boolean isIncluded(int value) { 731 for(Range r: ranges) { 732 if (r.start <= value && value <= r.end) { 733 return true; 734 } 735 } 736 return false; 737 } 738 //不解释 739 @Override 740 public String toString() { 741 StringBuffer result = new StringBuffer(); 742 boolean first = true; 743 for(Range r: ranges) { 744 if (first) { 745 first = false; 746 } else { 747 result.append(','); 748 } 749 result.append(r.start); 750 result.append('-'); 751 result.append(r.end); 752 } 753 return result.toString(); 754 } 755 } 756 //重写了toString方法 757 /** 758 * Parse the given attribute as a set of integer ranges 759 * @param name the attribute name 760 * @param defaultValue the default value if it is not set 761 * @return a new set of ranges from the configured value 762 */ 763 public IntegerRanges getRange(String name, String defaultValue) { 764 return new IntegerRanges(get(name, defaultValue)); 765 } 766 767 /** 768 * Get the comma delimited values of the <code>name</code> property as 769 * a collection of <code>String</code>s. 770 * If no such property is specified then empty collection is returned. 771 * <p> 772 * This is an optimized version of {@link #getStrings(String)} 773 * 774 * @param name property name. 775 * @return property value as a collection of <code>String</code>s. 776 */ 777 public Collection<String> getStringCollection(String name) { 778 String valueString = get(name); 779 return StringUtils.getStringCollection(valueString); 780 } 781 782 /** 783 * Get the comma delimited values of the <code>name</code> property as 784 * an array of <code>String</code>s. 785 * If no such property is specified then <code>null</code> is returned. 786 * 787 * @param name property name. 788 * @return property value as an array of <code>String</code>s, 789 * or <code>null</code>. 790 */ 791 public String[] getStrings(String name) { 792 String valueString = get(name); 793 return StringUtils.getStrings(valueString); 794 } 795 796 /** 797 * Get the comma delimited values of the <code>name</code> property as 798 * an array of <code>String</code>s. 799 * If no such property is specified then default value is returned. 800 * 801 * @param name property name. 802 * @param defaultValue The default value 803 * @return property value as an array of <code>String</code>s, 804 * or default value. 805 */ 806 public String[] getStrings(String name, String... defaultValue) { 807 String valueString = get(name); 808 if (valueString == null) { 809 return defaultValue; 810 } else { 811 return StringUtils.getStrings(valueString); 812 } 813 } 814 815 /** 816 * Set the array of string values for the <code>name</code> property as 817 * as comma delimited values. 818 * 819 * @param name property name. 820 * @param values The values 821 */ 822 public void setStrings(String name, String... values) { 823 set(name, StringUtils.arrayToString(values)); 824 } 825 826 /** 827 * Load a class by name. 828 * 829 * @param name the class name. 830 * @return the class object. 831 * @throws ClassNotFoundException if the class is not found. 832 */ 833 public Class<?> getClassByName(String name) throws ClassNotFoundException { 834
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