解释器模式
1.定义与类型
- 定义：给定一个语言，定义它的文法的一种示意，并定义一个解释器，这个解释器应用该示意来解释语言中的句子
- 为了解释一种语言，而为语言创立的解释器
- 类型：行为型
2.实用场景
- 某个特定类型问题产生频率足够高
3.长处
- 语法由很多类示意,容易扭转及扩大此语言
4.毛病
- 当语法规定数目太多，减少了零碎复杂度
5.相干设计模式
- 解释器模式和适配器模式
6.Coding
- 创立解释器顶级接口
public interface Interpreter { int interpreter();}- 解释器的相干实现类
public class AddInterpreter implements Interpreter{ private Interpreter firstExpression,secondExpression; public AddInterpreter(Interpreter firstExpression,Interpreter secondExpression){ this.firstExpression = firstExpression; this.secondExpression = secondExpression; } @Override public int interpreter() { return this.firstExpression.interpreter() + this.secondExpression.interpreter(); } @Override public String toString() { return "+"; }}public class MultiInterpreter implements Interpreter{ private Interpreter firstExpression,secondExpression; public MultiInterpreter(Interpreter firstExpression,Interpreter secondExpression){ this.firstExpression = firstExpression; this.secondExpression = secondExpression; } @Override public int interpreter() { return this.firstExpression.interpreter() * this.secondExpression.interpreter(); } @Override public String toString() { return "*"; }}- 创立数字解释器，用于解决入参
public class NumberInterpreter implements Interpreter { private int number; public NumberInterpreter(int number) { this.number = number; } public NumberInterpreter(String number) { this.number = Integer.parseInt(number); } @Override public int interpreter() { return this.number; }}- 简略实现一个工具类
public class OperatorUtil { public static boolean isOperator(String symbol) { return (symbol.equals("+") || symbol.equals("*")); } public static Interpreter getExpressionObjects(Interpreter firstInterpreter, Interpreter secondInterpreter, String symbol) { if ("+".equals(symbol)) { return new AddInterpreter(firstInterpreter, secondInterpreter); } else if ("*".equals(symbol)) { return new MultiInterpreter(firstInterpreter, secondInterpreter); } return null; }}- 自定义一个解释器语法
public class QchExpressionParser { private Stack<Interpreter> stack = new Stack<>(); public int parse(String str) { String[] strArray = str.split(" "); for (String item : strArray) { if (!OperatorUtil.isOperator(item)) { NumberInterpreter numberInterpreter = new NumberInterpreter(item); stack.push(numberInterpreter); System.out.println(String.format("入栈：%d", numberInterpreter.interpreter())); } else { Interpreter firstInterpreter = stack.pop(); Interpreter secondInterpreter = stack.pop(); System.out.println(String.format("出栈:%d 和 %d", firstInterpreter.interpreter(), secondInterpreter.interpreter())); Interpreter expressionObjects = OperatorUtil.getExpressionObjects(firstInterpreter, secondInterpreter, item); System.out.println(String.format("利用运算符: %s", expressionObjects.interpreter())); int result = expressionObjects.interpreter(); NumberInterpreter numberInterpreter = new NumberInterpreter(result); stack.push(numberInterpreter); System.out.println(String.format("阶段后果入栈:%d", result)); } } int result = stack.pop().interpreter(); return result; }}- Test测试类
public class Test { public static void main(String[] args) { String geelyInputStr = "6 100 11 + *"; QchExpressionParser expressionParser = new QchExpressionParser(); int parse = expressionParser.parse(geelyInputStr); System.out.println("解释器执行后果为:"+parse); }}- 控制台打印
7.源码
- Spring框架中的应用
public class TestForSpring { public static void main(String[] args) { ExpressionParser parser = new SpelExpressionParser(); Expression expression = parser.parseExpression("100 + 11 * 6"); int result = (int)expression.getValue(); System.out.println(result); }}debug看下源码
这个办法解决咱们的表达式
- 最初