@Lookup annotation Code

spring-core/src/main/java/com/baeldung/methodinjections/AppConfig.java

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+package com.baeldung.methodinjections;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan(basePackages = "com.baeldung.methodinjections")
+
+public class AppConfig {
+}

spring-core/src/main/java/com/baeldung/methodinjections/Grader.java

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+package com.baeldung.methodinjections;
+
+import java.util.Collection;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class Grader {
+
+    public String grade(Collection<Integer> marks) {
+
+        boolean result = marks.stream()
+            .anyMatch(mark -> mark < 45);
+        if (result) {
+            return "FAIL";
+        }
+        return "PASS";
+    }
+}

spring-core/src/main/java/com/baeldung/methodinjections/SchoolNotification.java

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+package com.baeldung.methodinjections;
+
+import java.util.ArrayList;
+import java.util.Collection;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.config.ConfigurableBeanFactory;
+import org.springframework.context.annotation.Scope;
+import org.springframework.stereotype.Component;
+
+@Component("schoolNotification")
+@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
+public class SchoolNotification {
+    @Autowired
+    Grader grader;
+
+    private String name;
+    private Collection<Integer> marks;
+
+    public SchoolNotification(String name) {
+        this.name = name;
+        this.marks = new ArrayList<Integer>();
+    }
+
+    public String addMark(Integer mark) {
+        this.marks.add(mark);
+        return this.grader.grade(this.marks);
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Collection<Integer> getMarks() {
+        return marks;
+    }
+
+    public void setMarks(Collection<Integer> marks) {
+        this.marks = marks;
+    }
+}

spring-core/src/main/java/com/baeldung/methodinjections/Student.java

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+package com.baeldung.methodinjections;
+
+import org.springframework.beans.factory.annotation.Lookup;
+import org.springframework.stereotype.Component;
+
+@Component("studentBean")
+public class Student {
+
+    private String id;
+
+    /**
+     * Injects a prototype bean SchoolNotification into Singleton student
+     */
+    @Lookup
+    public SchoolNotification getNotification(String name) {
+        // spring overrides and returns a SchoolNotification instance
+        return null;
+    }
+
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+}

spring-core/src/main/java/com/baeldung/methodinjections/StudentServices.java

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+package com.baeldung.methodinjections;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.springframework.beans.factory.annotation.Lookup;
+import org.springframework.stereotype.Component;
+
+@Component("studentService")
+public abstract class StudentServices {
+
+    private Map<String, SchoolNotification> notes = new HashMap<>();
+
+    @Lookup
+    protected abstract SchoolNotification getNotification(String name);
+
+    public String appendMark(String name, Integer mark) {
+        SchoolNotification notification = notes.computeIfAbsent(name, exists -> getNotification(name));
+        return notification.addMark(mark);
+    }
+}

spring-core/src/main/resources/beans.xml

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+<?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"
+	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">
+
+    <context:component-scan base-package="com.baeldung.methodinjections" />
+
+    <bean id="schoolNotification" class="com.baeldung.methodinjections.SchoolNotification" scope="prototype"/>
+
+    <bean id="studentServices" class="com.baeldung.methodinjections.StudentServices" scope="prototype" >
+    	<lookup-method name="getNotification" bean="schoolNotification"/>
+    </bean>     
+</beans>

spring-core/src/test/java/com/baeldung/methodinjections/StudentTest.java

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+package com.baeldung.methodinjections;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.support.ClassPathXmlApplicationContext;
+
+public class StudentTest {
+
+    @Test
+    public void whenLookupMethodCalled_thenNewInstanceReturned() {
+        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
+        Student student1 = context.getBean("studentBean", Student.class);
+        Student student2 = context.getBean("studentBean", Student.class);
+
+        Assert.assertEquals(student1, student2);
+        Assert.assertNotEquals(student1.getNotification("Alex"), student2.getNotification("Bethany"));
+        context.close();
+    }
+
+    @Test
+    public void whenAbstractGetterMethodInjects_thenNewInstanceReturned() {
+        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");
+        StudentServices services = context.getBean("studentServices", StudentServices.class);
+
+        Assert.assertEquals("PASS", services.appendMark("Alex", 76));
+        Assert.assertEquals("FAIL", services.appendMark("Bethany", 44));
+        Assert.assertEquals("PASS", services.appendMark("Claire", 96));
+        context.close();
+    }
+}