BAEL-1715- Control Bean Creation Order with @DependsOn annotation (#4028)

* removing Bean injection

* BAEL-1715- Control Bean Creation Order with @DependsOn annotation

* BAEL-1715- Formatting changes, test case improvement

* Created new Config file for UnitTest

* Corrected test case- from BeanCreationException to NoSuchBeanDefinitionException

* correcting error- for circular dependency expected exception is- BeanCreationException

spring-core/src/main/java/com/baeldung/dependson/DriverApplication.java

@@ -0,0 +1,14 @@
+package com.baeldung.dependson;
+
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import com.baeldung.dependson.config.Config;
+import com.baeldung.dependson.file.processor.FileProcessor;
+
+public class DriverApplication {
+    public static void main(String[] args) {
+        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(Config.class);
+        ctx.getBean(FileProcessor.class);
+        ctx.close();
+    }
+}

spring-core/src/main/java/com/baeldung/dependson/config/Config.java

@@ -0,0 +1,38 @@
+package com.baeldung.dependson.config;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.DependsOn;
+import org.springframework.context.annotation.Lazy;
+
+import com.baeldung.dependson.file.processor.FileProcessor;
+import com.baeldung.dependson.file.reader.FileReader;
+import com.baeldung.dependson.file.writer.FileWriter;
+import com.baeldung.dependson.shared.File;
+
+@Configuration
+@ComponentScan("com.baeldung.dependson")
+public class Config {
+    
+    @Autowired
+    File file;
+    
+    @Bean("fileProcessor")
+    @DependsOn({"fileReader","fileWriter"})
+    @Lazy
+    public FileProcessor fileProcessor(){
+        return new FileProcessor(file);
+    }
+    
+    @Bean("fileReader")
+    public FileReader fileReader(){
+        return new FileReader(file);
+    }
+    
+    @Bean("fileWriter")
+    public FileWriter fileWriter(){
+        return new FileWriter(file);
+    }
+}

spring-core/src/main/java/com/baeldung/dependson/file/processor/FileProcessor.java

@@ -0,0 +1,19 @@
+package com.baeldung.dependson.file.processor;
+
+import org.springframework.beans.factory.annotation.Autowired;
+
+import com.baeldung.dependson.file.reader.FileReader;
+import com.baeldung.dependson.file.writer.FileWriter;
+import com.baeldung.dependson.shared.File;
+
+public class FileProcessor {
+
+    File file;
+      
+    public FileProcessor(File file){
+        this.file = file;
+        if(file.getText().contains("write") && file.getText().contains("read")){
+            file.setText("processed");
+        }
+    }  
+}

spring-core/src/main/java/com/baeldung/dependson/file/reader/FileReader.java

@@ -0,0 +1,12 @@
+package com.baeldung.dependson.file.reader;
+
+import com.baeldung.dependson.shared.File;
+
+public class FileReader {
+
+    public FileReader(File file) {
+        file.setText("read");
+    }
+    
+    public void readFile() {}
+}

spring-core/src/main/java/com/baeldung/dependson/file/writer/FileWriter.java

@@ -0,0 +1,13 @@
+package com.baeldung.dependson.file.writer;
+
+import com.baeldung.dependson.shared.File;
+
+
+public class FileWriter {
+    
+    public FileWriter(File file){
+        file.setText("write");
+    }
+    
+    public void writeFile(){}
+}

spring-core/src/main/java/com/baeldung/dependson/shared/File.java

@@ -0,0 +1,17 @@
+package com.baeldung.dependson.shared;
+
+import org.springframework.stereotype.Service;
+
+@Service
+public class File {
+
+    private String text = "";
+
+    public String getText() {
+        return text;
+    }
+
+    public void setText(String text) {
+        this.text = this.text+text;
+    }
+}

spring-core/src/test/java/com/baeldung/dependson/config/TestConfig.java

@@ -0,0 +1,59 @@
+package com.baeldung.dependson.config;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.DependsOn;
+import org.springframework.context.annotation.Lazy;
+
+import com.baeldung.dependson.file.processor.FileProcessor;
+import com.baeldung.dependson.file.reader.FileReader;
+import com.baeldung.dependson.file.writer.FileWriter;
+import com.baeldung.dependson.shared.File;
+
+@Configuration
+@ComponentScan("com.baeldung.dependson")
+public class TestConfig {
+    
+    @Autowired
+    File file;
+    
+    @Bean("fileProcessor")
+    @DependsOn({"fileReader","fileWriter"})
+    @Lazy
+    public FileProcessor fileProcessor(){
+        return new FileProcessor(file);
+    }
+    
+    @Bean("fileReader")
+    public FileReader fileReader(){
+        return new FileReader(file);
+    }
+    
+    @Bean("fileWriter")
+    public FileWriter fileWriter(){
+        return new FileWriter(file);
+    }
+    
+    @Bean("dummyFileProcessor")
+    @DependsOn({"dummyfileWriter"})
+    @Lazy
+    public FileProcessor dummyFileProcessor(){
+        return new FileProcessor(file);
+    }
+    
+    @Bean("dummyFileProcessorCircular")
+    @DependsOn({"dummyFileReaderCircular"})
+    @Lazy
+    public FileProcessor dummyFileProcessorCircular(){
+        return new FileProcessor(file);
+    }
+    
+    @Bean("dummyFileReaderCircular")
+    @DependsOn({"dummyFileProcessorCircular"})
+    @Lazy
+    public FileReader dummyFileReaderCircular(){
+        return new FileReader(file);
+    }
+}

spring-core/src/test/java/com/baeldung/dependson/processor/FileProcessorTest.java

@@ -0,0 +1,42 @@
+package com.baeldung.dependson.processor;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.BeanCreationException;
+import org.springframework.beans.factory.NoSuchBeanDefinitionException;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.ApplicationContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+import com.baeldung.dependson.config.TestConfig;
+import com.baeldung.dependson.shared.File;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(classes = TestConfig.class)
+public class FileProcessorTest {
+
+    @Autowired
+    ApplicationContext context;
+    
+    @Autowired
+    File file;
+    
+    @Test
+    public void whenAllBeansCreated_FileTextEndsWithProcessed() {
+        context.getBean("fileProcessor");
+        assertTrue(file.getText().endsWith("processed"));
+    }
+
+    @Test(expected=NoSuchBeanDefinitionException.class)
+    public void whenDependentBeanNotAvailable_ThrowsNoSuchBeanDefinitionException(){
+        context.getBean("dummyFileProcessor");
+    }
+    
+    @Test(expected=BeanCreationException.class)
+    public void whenCircularDependency_ThrowsBeanCreationException(){
+        context.getBean("dummyFileReaderCircular");
+    }
+}