Spring-PathMatcher-路径匹配器

1. 概述

PathMatcher是Spring的一个概念模型接口，该接口抽象建模了概念"路径匹配器"，一个"路径匹配器"是一个用于路径匹配的工具。

位于 Spring-core 包中 util 包下。

2. PathMatcher 接口源码

package org.springframework.util;

import java.util.Comparator;
import java.util.Map;

public interface PathMatcher {

	/**
	 * Does the given path represent a pattern that can be matched
	 * by an implementation of this interface?
	 * 判断指定的路径 path 是否是一个 pattern(模式)
	 * 如果返回值是 false，也就是说 path 不是一个模式，而是一个静态路径(真正的路径字符串),
	 * 那么就不用调用方法 #match 了，因为对于静态路径的匹配，直接使用字符串等号比较就足够了。
	 * @param path the path String to check
	 * @return true if the given path represents a pattern
	 */
	boolean isPattern(String path);

	/**
	 * Match the given path against the given pattern,
	 * according to this PathMatcher's matching strategy.
	 * 根据当前 PathMatcher 的匹配策略，检查指定的径 path 和指定的模式 pattern 是否匹配
	 * @param 用于检测路径字符串是否匹配于某个模式时所用的模式
	 * @param path 需要被检测的路径字符串
	 * @return true 表示匹配， false 表示不匹配
	 */
	boolean match(String pattern, String path);

	/**
	 * Match the given  path against the corresponding part of the given
	 * pattern, according to this PathMatcher's matching strategy.
	 * 根据当前 PathMatcher 的匹配策略，检查指定的径 path 和指定的模式 pattern 是否之间
	 * 是否为前缀匹配
	 * @param pattern the pattern to match against
	 * @param path the path String to test
	 * @return true 表示匹配， false 表示不匹配
	 */
	boolean matchStart(String pattern, String path);

	/**
	 * Given a pattern and a full path, determine the pattern-mapped part.
	 * 给定一个模式 pattern 和一个全路径 path，判断路径中和模式匹配的部分。
     *
	 * This method is supposed to find out which part of the path is matched
	 * dynamically through an actual pattern, that is, it strips off a statically
	 * defined leading path from the given full path, returning only the actually
	 * pattern-matched part of the path.
	 * 该方法用于发现路径中的哪一部分是和模式能动态匹配上的部分。它会去除路径中开头静态部分，
	 * 仅仅返回那部分真正和模式匹配的上的部分。
	 * 例子 : "myroot/*.html" 为 pattern , "myroot/myfile.html" 为路径，
	 *  则该方法返回 "myfile.html".  
	 * 具体的检测规则根据当前 PathMatcher 的匹配策略来顶。	
	 * A simple implementation may return the given full path as-is in case
	 * of an actual pattern, and the empty String in case of the pattern not
	 * containing any dynamic parts (i.e. the pattern parameter being
	 * a static path that wouldn't qualify as an actual #isPattern pattern.
	 * A sophisticated implementation will differentiate between the static parts
	 * and the dynamic parts of the given path pattern.
	 * @param pattern the path pattern
	 * @param path the full path to introspect
	 * @return the pattern-mapped part of the given path
	 * (never null)
	 */
	String extractPathWithinPattern(String pattern, String path);

	/**
	 * Given a pattern and a full path, extract the URI template variables. URI template
	 * variables are expressed through curly brackets ('{' and '}').
	 * 给定一个模式和一个路径，提取其中的 URI 模板变量信息。URI模板变量表达式格式为 "{variable}"
	 *      
	 * 例子 : pattern  为 "/hotels/{hotel}" ，路径为 "/hotels/1", 则该方法会返回一个 map ，
     * 内容为 : "hotel"->"1".
	 * @param pattern the path pattern, possibly containing URI templates
	 * @param path the full path to extract template variables from
	 * @return a map, containing variable names as keys; variables values as values
	 */
	Map<String, String> extractUriTemplateVariables(String pattern, String path);

	/**
	 * Given a full path, returns a Comparator suitable for sorting patterns
	 * in order of explicitness for that path.
	 * The full algorithm used depends on the underlying implementation,
	 * but generally, the returned Comparator will sort a list so that more 
     * specific patterns come before generic patterns.
	 * @param path the full path to use for comparison
	 * @return a comparator capable of sorting patterns in order of explicitness
	 */
	Comparator<String> getPatternComparator(String path);

	/**
	 * Combines two patterns into a new pattern that is returned.
	 * The full algorithm used for combining the two pattern depends on the underlying implementation.
	 * 合并两个模式。具体合并的算法由实现类决定。
	 * @param pattern1 the first pattern
	 * @param pattern2 the second pattern
	 * @return the combination of the two patterns
	 * @throws IllegalArgumentException when the two patterns cannot be combined
	 */
	String combine(String pattern1, String pattern2);

}

3. AntPathMatcher

Spring框架自身对概念模型接口也提供了一个缺省的实现AntPathMatcher,用于匹配Ant风格的路径。我们平时使用的路径匹配基本用的都是这个。

1. 通配符

• ? 表示匹配任意一个字符

System.out.println( matcher.match("/usr/name?", "/usr/name1") );  //true
System.out.println( matcher.match("/usr/name?", "/usr/name111") );  //false

• * 表示匹配单个路径

System.out.println( matcher.match("/usr/*", "/usr/list")); //true
System.out.println( matcher.match("/usr/*", "/usr/list/again")); //false
System.out.println( matcher.match("/usr/*.app", "/usr/list.app")); //true
System.out.println( matcher.match("/usr/*.app", "/usr/list.html")); //false

• ** 表示匹配多级路径

System.out.println( matcher.match("/usr/**", "/usr/list") );  //true
System.out.println( matcher.match("/usr/**", "/usr/list/again") );  //true

• 通过 extractPathWithinPattern() 方法匹配

/**
 * extractPathWithinPattern 返回符合匹配的部分路径，去除路径开头静态部分
 **/
System.out.println( matcher.extractPathWithinPattern("/usr/*", "/usr/list") );   //list
System.out.println( matcher.extractPathWithinPattern("/usr/*/again", "/usr/list/again/age") );   // list/again/age
System.out.println( matcher.extractPathWithinPattern("/usr/*.html", "/usr/list") );  //list
System.out.println( matcher.extractPathWithinPattern("/usr/*.html", "/usr/list.html") );  //list.html

2. 变量绑定

变量绑定可以让我们在匹配过程中提取路径中的参数，并将其赋值给指定的变量。

System.out.println( matcher.extractUriTemplateVariables("/usr/{name}/{age}", "/usr/张三/12") ); //{name=张三, age=12}