Getting Dynamic Values From method Parameters in Custom Annotations using Spring AOP
Dependency for spring core and spring aop
<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>com.demo</groupId>
<artifactId>SpringAOP</artifactId>
<packaging>jar</packaging>
<version>1.0-SNAPSHOT</version>
<name>SpringAOP</name>
<url>http://maven.apache.org</url>
<properties>
<spring.version>4.1.1.RELEASE</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>1.6.11</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>1.6.11</version>
</dependency>
</dependencies>
<build>
<finalName>SpringApp</finalName>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.6</source>
<target>1.6</target>
</configuration>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<configuration>
<includes>
<include>**/*Tests.java</include>
</includes>
</configuration>
</plugin>
</plugins>
</build>
</project>This project requires dependencies for spring-core and spring-aop to be included.
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">
<context:annotation-config/>
<context:component-scan base-package="com.demo"/>
<aop:aspectj-autoproxy/>
</beans>package com.demo;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface CustomAnnotation {
/**
* Spring Expression Language (SpEL) attribute for computing the key dynamically.
*/
String key();
}"key" in this annotation will contain the parameters which will be calculated dynamically.
package com.demo;
public class User {
private String firstName;
private String lastName;
private Long age;
private Address address;
private Long id;
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public Long getAge() {
return age;
}
public void setAge(Long age) {
this.age = age;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public User(String firstName, String lastName, Long age) {
this.firstName = firstName;
this.lastName = lastName;
this.age = age;
}
public User(Address address) {
this.address = address;
}
}
package com.demo;
public class Address {
private String city;
private String state;
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getState() {
return state;
}
public void setState(String state) {
this.state = state;
}
public Address(String city, String state) {
this.city = city;
this.state = state;
}
}package com.demo;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.stereotype.Component;
import java.lang.reflect.Method;
@Aspect
@Component
public class AnnotationAspect {
@Before("methodsAnnotatedWithCustomAnnotation()")
public void processMethodsAnnotatedWithCustomAnnotation(JoinPoint joinPoint) {
System.out.println("-> processMethodsAnnotatedWithCustomAnnotation starts");
MethodSignature signature = (MethodSignature) joinPoint.getSignature();
Method method = signature.getMethod();
CustomAnnotation customAnnotation = method.getAnnotation(CustomAnnotation.class);
Object dynamicValue = CustomSpringExpressionLanguageParser.
getDynamicValue(signature.getParameterNames(), joinPoint.getArgs(), customAnnotation.key());
System.out.println("Dynamic Value Fetched is:: " + dynamicValue);
}
@Pointcut("@annotation(com.demo.CustomAnnotation)")
private void methodsAnnotatedWithCustomAnnotation() {
}
}package com.demo;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
public class CustomSpringExpressionLanguageParser {
public static Object getDynamicValue(String[] parameterNames, Object[] args, String key) {
ExpressionParser parser = new SpelExpressionParser();
StandardEvaluationContext context = new StandardEvaluationContext();
for (int i = 0; i < parameterNames.length; i++) {
context.setVariable(parameterNames[i], args[i]);
}
return (Object) parser.parseExpression(key).getValue(context, Object.class);
}
}This is a custom Spring EL parser that takes key whise value is to be found, value array of arguments and array of parameter names.
package com.demo;
import org.springframework.stereotype.Component;
@Component
public class UserService {
@CustomAnnotation(key = "#firstName")
public void getUserFirstName(String firstName) {
System.out.println("getUserFirstName");
// business logic
}
@CustomAnnotation(key = "#user.age")
public void getUserAge(User user) {
System.out.println("getUserAge");
// business logic
}
@CustomAnnotation(key = "#user.address.city")
public void getUserCity(User user) {
System.out.println("getUserCity");
// business logic
}
}
This service contains test methods which take key as flat String ("#firstName"), nested fields (#user.age) and fields inside nested objects ("#user.address.city)
package com.demo;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class TestMain {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("spring-config.xml");
UserService userService = context.getBean(UserService.class);
userService.getUserFirstName("Dummy User");
userService.getUserAge(new User("Dummy", "User", 30l));
userService.getUserCity(new User(new Address("Noida", "UP")));
}
}-> processMethodsAnnotatedWithCustomAnnotation starts
Dynamic Value Fetched is:: Dummy User
getUserFirstName
-> processMethodsAnnotatedWithCustomAnnotation starts
Dynamic Value Fetched is:: 30
getUserAge
-> processMethodsAnnotatedWithCustomAnnotation starts
Dynamic Value Fetched is:: Noida
getUserCity