Aop中使用SPEL
# Aop中使用SPEL
在AOP中使用spel动态获取别切的方法的入参信息
# 1. 什么是SPEL
全称为 Spring Expression Language
, 能在运行时构建复杂表达式、存取对象图属性、对象方法调用等等,并且能与Spring功能完美整合. SpEL是单独模块,只依赖于core模块,不依赖于其他模块,可以单独使用.
需要引入 org.springframework.expression
.
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.example</groupId>
<artifactId>test</artifactId>
<packaging>jar</packaging>
<version>1.0-SNAPSHOT</version>
<name>test</name>
<properties>
<java.version>1.8</java.version>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<spring-boot.version>2.7.1</spring-boot.version>
</properties>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>${spring-boot.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-expression</artifactId>
</dependency>
</dependencies>
</project>
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# 2. API式调用
package org.example;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
/**
* Test1
*
* @author 董新平
* @since 2022/9/5 11:50
*/
public class Test1 {
public static void main(String[] args) {
ExpressionParser parser = new SpelExpressionParser();
Expression expression = parser.parseExpression("('123' + ' 456').concat(#end)");
EvaluationContext context = new StandardEvaluationContext();
context.setVariable("end", "789");
// 123 456789
System.out.println(expression.getValue(context));
}
}
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# 3. 结合AOP调用
# 3.1 引用
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-aop</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
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# 3.2 自定义注解+aop
/**
* Demo
*
* @author 董新平
* @since 2022/9/5 12:06
*/
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Demo {
String spel();
}
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@Aspect
@Component
public class DemoAspects {
@AfterReturning("@annotation(org.example.aop.Demo) && @annotation(demo)")
public void log(JoinPoint joinPoint, Demo demo) {
String value = SpELUtil.getValue(joinPoint, demo);
System.out.println("aop ===> " + value);
}
}
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@Component
public class Test2 {
@Demo(spel = "#name")
public String test(String name) {
return "ok";
}
}
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工具包
package org.example.aop;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import java.util.Arrays;
import java.util.List;
/**
* SpELUtil
*
* @author 董新平
* @since 2022/9/5 12:29
*/
public class SpELUtil {
/**
* SpEL解析器
*/
private static final SpelExpressionParser spelParser = new SpelExpressionParser();
/**
* 获取spel中的数据
*/
public static String getValue(JoinPoint joinPoint, Demo demo) {
//获取方法的参数名和参数值
MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
List<String> paramNameList = Arrays.asList(methodSignature.getParameterNames());
List<Object> paramList = Arrays.asList(joinPoint.getArgs());
//将方法的参数名和参数值一一对应的放入上下文中
EvaluationContext ctx = new StandardEvaluationContext();
for (int i = 0; i < paramNameList.size(); i++) {
ctx.setVariable(paramNameList.get(i), paramList.get(i));
}
// 解析SpEL表达式获取结果
Object value = spelParser.parseExpression(demo.spel()).getValue(ctx);
if (value == null){
return "";
}else {
return value.toString();
}
}
}
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test测试类
@RunWith(SpringRunner.class)
@SpringBootTest
public class AppTest {
@Autowired
private Test2 test2;
@Test
public void test(){
System.out.println(test2.test("张三"));
}
}
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AOP类将会输出 aop ===> 张三
# 4.spel常用语法
package org.example;
import org.example.aop.Test2;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.context.ApplicationContext;
import org.springframework.context.expression.BeanFactoryResolver;
import org.springframework.expression.Expression;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.test.context.junit4.SpringRunner;
import java.util.Arrays;
@RunWith(SpringRunner.class)
@SpringBootTest()
public class Test3 {
@Autowired
private ApplicationContext applicationContext;
@Test
public void test() {
ExpressionParser parser = new SpelExpressionParser();
// 括号优先, #号读取 context 中的变量值, String 的方法全部可用 concat
Expression expression = parser.parseExpression("('123' + ' 456').concat(#end)");
StandardEvaluationContext context = new StandardEvaluationContext();
context.setVariable("end", "789");
System.out.println(expression.getValue(context)); //123 456789
// 基本的计算 (+,-,*,/), 比较符号 ==, !=, "EQ” 、“NE”、 “GT”、“GE”、 “LT” 、“LE”
expression = parser.parseExpression("(1+2) EQ #value");
context = new StandardEvaluationContext();
context.setVariable("value", 3);
System.out.println(expression.getValue(context)); // true
// 索引,截取
expression = parser.parseExpression("'abcd'[1]");
System.out.println(expression.getValue(context)); // b
//三目运算及Elivis运算表达式, 等价写法
expression = parser.parseExpression("#a != null?#a:'b'");
//expression = parser.parseExpression("#a?:'b'");
context = new StandardEvaluationContext();
context.setVariable("a", null);
System.out.println(expression.getValue(context)); // b
// 正则表达式
expression = parser.parseExpression("#name matches '\\d{3}'");
context = new StandardEvaluationContext();
context.setVariable("name", "123");
System.out.println("正则 ==> " + expression.getValue(context)); // true
// 赋值
expression = parser.parseExpression("#user.name='bbb'");
context = new StandardEvaluationContext();
User user = new User("aaa");
context.setVariable("user", user);
expression.getValue(context);
System.out.println("赋值 ==> " + user.getName()); // bbb
// 实例化对象
expression = parser.parseExpression("new org.example.User('bbb')");
User value = (User) expression.getValue();
System.out.println("实例化对象 ==> " + value.getName()); // bbb
// 静态方法调用
expression = parser.parseExpression("T(java.lang.Math).round(3.14)");
System.out.println("静态方法调用 ==> " + expression.getValue()); // 3
// Bean引用
expression = parser.parseExpression("@test2.test('123')");
context = new StandardEvaluationContext();
context.setBeanResolver(new BeanFactoryResolver(applicationContext));
System.out.println("Bean引用 ==> " + expression.getValue(context)); // OK
// 集合, 过滤值大于4的
expression = parser.parseExpression("#collection.?[#this>4]");
context = new StandardEvaluationContext();
context.setVariable("collection", Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8));
System.out.println("集合 ==> " + expression.getValue(context)); // [5, 6, 7, 8]
}
}
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案例中用到的User类
package org.example;
/**
* User
*
* @author 董新平
* @since 2022/9/5 14:07
*/
public class User {
public User(String name) {
this.name = name;
}
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
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案例中的test2在3中已经声明
上次更新: 2023/06/12, 10:31:06