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类型#xff1a; 行为型模式 目的 行为型模式 目的 实现了一个表达式接口该接口解释一个特定的上下文。这种模式被用在 SQL 解析、符号处理引擎等
二、例子
2.1 菜鸟教程例子
2.1.1 定义一个表达式接口
public interface Expression {public boolean interpret(String context);
}
2.1.2 实现Expression接口
public class TerminalExpression implements Expression {private String data;public TerminalExpression(String data){this.data data; }Overridepublic boolean interpret(String context) {if(context.contains(data)){return true;}return false;}
}public class OrExpression implements Expression {private Expression expr1 null;private Expression expr2 null;public OrExpression(Expression expr1, Expression expr2) { this.expr1 expr1;this.expr2 expr2;}Overridepublic boolean interpret(String context) { return expr1.interpret(context) || expr2.interpret(context);}
}public class AndExpression implements Expression {private Expression expr1 null;private Expression expr2 null;public AndExpression(Expression expr1, Expression expr2) { this.expr1 expr1;this.expr2 expr2;}Overridepublic boolean interpret(String context) { return expr1.interpret(context) expr2.interpret(context);}
}2.1.3 定义解析规则
public class Expressions {//规则Robert 和 John 是男性public static Expression getMaleExpression(){Expression robert new TerminalExpression(Robert);Expression john new TerminalExpression(John);return new OrExpression(robert, john); }//规则Julie 是一个已婚的女性public static Expression getMarriedWomanExpression(){Expression julie new TerminalExpression(Julie);Expression married new TerminalExpression(Married);return new AndExpression(julie, married); }
}2.1.4 使用
public class InterpreterPatternDemo {public static void main(String[] args) {Expression isMale Expressions.getMaleExpression();System.out.println(John is male? isMale.interpret(John));Expression isMarriedWoman Expressions.getMarriedWomanExpression();System.out.println(Julie is a married women? isMarriedWoman.interpret(Married Julie));}
}2.2 JDK源码——Pattern
public final class Pattern implements java.io.Serializable {public static Pattern compile(String regex) {return new Pattern(regex, 0);}public static Pattern compile(String regex, int flags) {return new Pattern(regex, flags);}private String pattern;public String pattern() {return pattern;}private Pattern(String p, int f) {if ((f ~ALL_FLAGS) ! 0) {throw new IllegalArgumentException(Unknown flag 0x Integer.toHexString(f));}pattern p;flags f;// to use UNICODE_CASE if UNICODE_CHARACTER_CLASS presentif ((flags UNICODE_CHARACTER_CLASS) ! 0)flags | UNICODE_CASE;// flags for compilingflags0 flags;// Reset group index countcapturingGroupCount 1;localCount 0;localTCNCount 0;if (!pattern.isEmpty()) {try {compile();} catch (StackOverflowError soe) {throw error(Stack overflow during pattern compilation);}} else {root new Start(lastAccept);matchRoot lastAccept;}} private void compile() {.....}
}static class Start extends Node {int minLength;Start(Node node) {this.next node;TreeInfo info new TreeInfo();next.study(info);minLength info.minLength;}......
}static final class StartS extends Start {StartS(Node node) {super(node);}
}static final class Begin extends Node {boolean match(Matcher matcher, int i, CharSequence seq) {.......}
}static final class End extends Node {boolean match(Matcher matcher, int i, CharSequence seq) {...}
}2.3 Spring源码——ExpressionParser
public interface ExpressionParser {Expression parseExpression(String expressionString) throws ParseException;Expression parseExpression(String expressionString, ParserContext context) throws ParseException;
}
public class SpelExpressionParser extends TemplateAwareExpressionParser {private final SpelParserConfiguration configuration;public SpelExpressionParser() {this.configuration new SpelParserConfiguration();}public SpelExpressionParser(SpelParserConfiguration configuration) {Assert.notNull(configuration, SpelParserConfiguration must not be null);this.configuration configuration;}public SpelExpression parseRaw(String expressionString) throws ParseException {Assert.hasText(expressionString, expressionString must not be null or blank);return this.doParseExpression(expressionString, (ParserContext)null);}protected SpelExpression doParseExpression(String expressionString, Nullable ParserContext context) throws ParseException {return (new InternalSpelExpressionParser(this.configuration)).doParseExpression(expressionString, context);}
}
class InternalSpelExpressionParser extends TemplateAwareExpressionParser {private final DequeSpelNodeImpl constructedNodes new ArrayDeque();protected SpelExpression doParseExpression(String expressionString, Nullable ParserContext context) throws ParseException {this.checkExpressionLength(expressionString);try {this.expressionString expressionString;Tokenizer tokenizer new Tokenizer(expressionString);this.tokenStream tokenizer.process();this.tokenStreamLength this.tokenStream.size();this.tokenStreamPointer 0;this.constructedNodes.clear();SpelNodeImpl ast this.eatExpression();if (ast null) {throw new SpelParseException(this.expressionString, 0, SpelMessage.OOD, new Object[0]);} else {Token t this.peekToken();if (t ! null) {throw new SpelParseException(this.expressionString, t.startPos, SpelMessage.MORE_INPUT, new Object[]{this.toString(this.nextToken())});} else {return new SpelExpression(expressionString, ast, this.configuration);}}} catch (InternalParseException var6) {throw var6.getCause();}}}三、其他设计模式
创建型模式 结构型模式
1、设计模式——装饰器模式Decorator Pattern Spring相关源码
行为型模式
1、设计模式——访问者模式Visitor Pattern Spring相关源码2、设计模式——中介者模式Mediator Pattern JDK相关源码3、设计模式——策略模式Strategy Pattern Spring相关源码4、设计模式——状态模式State Pattern5、设计模式——命令模式Command Pattern Spring相关源码6、设计模式——观察者模式Observer Pattern Spring相关源码7、设计模式——备忘录模式Memento Pattern8、设计模式——模板方法模式Template Pattern Spring相关源码9、设计模式——迭代器模式Iterator Pattern Spring相关源码10、设计模式——责任链模式Chain of Responsibility Pattern Spring相关源码11、设计模式——解释器模式Interpreter Pattern Spring相关源码
