Domov arrow Programovanie arrow Hľadanie anotovaných komponentov
Hľadanie anotovaných komponentov

javaVytvoríme si vlastnú anotáciu pre triedy. Potom niekoľko tried roztrúsime po packageoch a necháme Springové záležitosti, aby našli tie správne triedy a potom jednej z nich aj zavoláme.

DOWNLOAD CODE HERE. Tu si stiahni cely projekt. Malicke to je. Par tried. Vyskusaj.

Toľko toho bolo na začiatku - malá nočná hudba o troch súboroch. Zožeň Maven. Otvor cmd v adresári kde je kód a píš: "mvn install eclipse:eclipse" A ideš!

Image
zaciname odtial - prazdny projekt

pom.xml

<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.perhac.blog</groupId>

  <artifactId>component-scanning</artifactId>

  <packaging>jar</packaging>

  <version>1.0-SNAPSHOT</version>

  <name>ComponentScanning</name>

  <description>This will use Spring internals to scan for classes annotated with a custom annotation. Spring core/beans/context version 2.5+ required to run this example. Java 7 used, but not required.</description>

 

  <properties>

    <spring.version>4.1.2.RELEASE</spring.version>

  </properties>

 

  <dependencies>

 

    <!-- Spring framework -->

   

    <dependency>

      <groupId>org.springframework</groupId>

      <artifactId>spring-core</artifactId>

      <version>${spring.version}</version>

    </dependency>

    <dependency>

      <groupId>org.springframework</groupId>

      <artifactId>spring-beans</artifactId>

      <version>${spring.version}</version>

    </dependency>

    <dependency>

      <groupId>org.springframework</groupId>

      <artifactId>spring-context</artifactId>

      <version>${spring.version}</version>

    </dependency>

   

    <!-- logging: logback over slf4j, because it rocks! -->

    <dependency>

      <groupId>org.slf4j</groupId>

      <artifactId>slf4j-api</artifactId>

      <version>1.7.7</version>

    </dependency>

    <dependency>

      <groupId>ch.qos.logback</groupId>

      <artifactId>logback-classic</artifactId>

      <version>1.1.2</version>

    </dependency>

  </dependencies>

  <build>

    <plugins>

      <plugin>

        <artifactId>maven-compiler-plugin</artifactId>

        <version>3.2</version>

        <configuration>

          <source>1.7</source>

          <target>1.7</target>

        </configuration>

      </plugin>

      <plugin>

        <groupId>org.apache.maven.plugins</groupId>

        <artifactId>maven-eclipse-plugin</artifactId>

        <version>2.9</version>

        <configuration>

          <downloadSources>true</downloadSources>

          <downloadJavadocs>true</downloadJavadocs>

        </configuration>

      </plugin>

    </plugins>

  </build>

 

</project>

logback.xml

<configuration>

 

  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">

    <!-- encoders are assigned the type

         ch.qos.logback.classic.encoder.PatternLayoutEncoder by default -->

    <encoder>

      <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>

    </encoder>

  </appender>

 

  <root level="debug">

    <appender-ref ref="STDOUT" />

  </root>

</configuration>

FindComponents.java (first-stab)

package com.perhac.blog.component_scanning;

 

import java.io.IOException;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

 

public class FindComponents {

 

       private static final Logger LOG = LoggerFactory.getLogger(FindComponents.class);

 

       public static void main(String[] args) throws IOException {

              LOG.info("Ready to roll!");

       }

 

}

 

Tak si vytvorme niekolko tried, co poanotujeme novou anotaciou:

MyComponent.java (annotation)

package com.perhac.blog.component_scanning;

 

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.TYPE)

public @interface MyComponent {

 

       String value();

}

 

A potom dopiseme tento kod do FindComponents triedy. Toto spusti hladanie anotovanych tried vsade v urcenom package-i a package-och v nom ulozenych.

FindComponents.java (imporved - finds annotated classes)

package com.perhac.blog.component_scanning;

 

import java.util.HashSet;

import java.util.Set;

 

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.beans.factory.config.BeanDefinition;

import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;

import org.springframework.core.type.filter.AnnotationTypeFilter;

 

public class FindComponents {

 

       private static final Logger LOG = LoggerFactory.getLogger(FindComponents.class);

 

       private static final String BASE_PACKAGE = FindComponents.class.getPackage().getName();

 

       public static void main(String[] args) throws Exception {

              LOG.info("Ready to roll!");

 

              Set<Class<?>> myComponentClasses = findAnnotatedClasses(BASE_PACKAGE);

              for (Class<?> myClass : myComponentClasses) {

                     MyComponent annotation = myClass.getAnnotation(MyComponent.class);

                     LOG.info("Found name: \"{}\" of type: {}", annotation.value(), myClass.getName());

              }

       }

 

       private static Set<Class<?>> findAnnotatedClasses(String basePackage) throws ClassNotFoundException {

              ClassPathScanningCandidateComponentProvider componentProvider = new ClassPathScanningCandidateComponentProvider(false);

              componentProvider.addIncludeFilter(new AnnotationTypeFilter(MyComponent.class));

              Set<BeanDefinition> candidateComponents = componentProvider.findCandidateComponents(basePackage);

              Set<Class<?>> classesFound = new HashSet<>();

              for (BeanDefinition beanDefinition : candidateComponents) {

                     classesFound.add(Class.forName(beanDefinition.getBeanClassName()));

              }

              return classesFound;

       }

 

}

 

Takto jednu z tried vyberieme a spustime jej main() methodu pomocou reflection:

FindComponents.java (final)

package com.perhac.blog.component_scanning;

 

import java.lang.reflect.Method;

import java.util.HashMap;

import java.util.HashSet;

import java.util.Map;

import java.util.Set;

 

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.beans.factory.config.BeanDefinition;

import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;

import org.springframework.core.type.filter.AnnotationTypeFilter;

 

public class FindComponents {

 

       private static final Logger LOG = LoggerFactory.getLogger(FindComponents.class);

 

       private static final String BASE_PACKAGE = FindComponents.class.getPackage().getName();

 

       public static void main(String[] args) throws Exception {

              LOG.info("Ready to roll!");

 

              Set<Class<?>> myComponentClasses = findAnnotatedClasses(BASE_PACKAGE);

              Map<String, Class<?>> classMap = new HashMap<>();

              for (Class<?> myClass : myComponentClasses) {

                     MyComponent annotation = myClass.getAnnotation(MyComponent.class);

                     LOG.info("Found name: \"{}\" of type: {}", annotation.value(), myClass.getName());

                     classMap.put(annotation.value(), myClass);

              }

 

              Class<?> classToRun = classMap.get("hidden");

              Method mainMethod = classToRun.getMethod("main", String[].class);

              mainMethod.invoke(null, new Object[] { new String[] { "Peter Perhac", "Brighton, UK", "November 25, 2014" } });

       }

 

       private static Set<Class<?>> findAnnotatedClasses(String basePackage) throws ClassNotFoundException {

              ClassPathScanningCandidateComponentProvider componentProvider = new ClassPathScanningCandidateComponentProvider(false);

              componentProvider.addIncludeFilter(new AnnotationTypeFilter(MyComponent.class));

              Set<BeanDefinition> candidateComponents = componentProvider.findCandidateComponents(basePackage);

              Set<Class<?>> classesFound = new HashSet<>();

              for (BeanDefinition beanDefinition : candidateComponents) {

                     classesFound.add(Class.forName(beanDefinition.getBeanClassName()));

              }

              return classesFound;

       }

 

}

 

Takto to vyzera u mna v projekte, vy ste si mozno vykuzlili ine triedy. Je jedno ake, kym ste ich anotovali @MyComponent.

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finalna verzia - vsetky subory projektu

Zvolenu triedu HiddenClass.java uvediem pre kompletnost:

HiddenClass.java

package com.perhac.blog.component_scanning.dummy.nested;

 

import java.util.Arrays;

 

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

 

import com.perhac.blog.component_scanning.MyComponent;

 

@MyComponent("hidden")

public class HiddenClass {

 

       private static final Logger LOG = LoggerFactory.getLogger(HiddenClass.class);

 

       public static void main(String[] args) {

              LOG.info("Hello from: " + HiddenClass.class.getName());

              LOG.debug(Arrays.toString(args));

       }

 

}

 

A vysledok prenadherny, ako sa dalo cakat:

21:50:09.211 [main] INFO  c.p.b.c.FindComponents - Ready to roll!

21:50:09.371 [main] INFO  c.p.b.c.FindComponents - Found name: "two" of type: com.perhac.blog.component_scanning.another_dummy.ClassTwo

21:50:09.371 [main] INFO  c.p.b.c.FindComponents - Found name: "one" of type: com.perhac.blog.component_scanning.dummy.ClassOne

21:50:09.371 [main] INFO  c.p.b.c.FindComponents - Found name: "hidden" of type: com.perhac.blog.component_scanning.dummy.nested.HiddenClass

21:50:09.371 [main] INFO  c.p.b.c.dummy.nested.HiddenClass - Hello from: com.perhac.blog.component_scanning.dummy.nested.HiddenClass

21:50:09.371 [main] DEBUG c.p.b.c.dummy.nested.HiddenClass - [Peter Perhac, Brighton, UK, November 25, 2014]

 

DOWNLOAD CODE HERE. Tu si stiahni cely projekt. Malicke to je. Par tried. Vyskusaj.
Posledná úprava ( Tuesday, 25 November 2014 )
 
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