BAEL-2569 : EnvironmentPostProcessor in Spring Boot (#6479)

* BAEL-2569 : EnvironmentPostProcessor in Spring Boot

* BAEL-2569 add test

* BAEL-2569 update test

spring-boot/src/main/java/com/baeldung/environmentpostprocessor/PriceCalculationApplication.java

@@ -0,0 +1,59 @@
+package com.baeldung.environmentpostprocessor;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.CommandLineRunner;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+import com.baeldung.environmentpostprocessor.service.PriceCalculationService;
+
+@SpringBootApplication
+public class PriceCalculationApplication implements CommandLineRunner {
+
+    @Autowired
+    PriceCalculationService priceCalculationService;
+
+    private static final Logger logger = LoggerFactory.getLogger(PriceCalculationApplication.class);
+
+    public static void main(String[] args) {
+        SpringApplication.run(PriceCalculationApplication.class, args);
+    }
+
+    @Override
+    public void run(String... args) throws Exception {
+
+        List<String> params = Arrays.stream(args)
+            .collect(Collectors.toList());
+        if (verifyArguments(params)) {
+            double singlePrice = Double.valueOf(params.get(0));
+            int quantity = Integer.valueOf(params.get(1));
+            priceCalculationService.productTotalPrice(singlePrice, quantity);
+        } else {
+            logger.error("Invalid arguments " + params.toString());
+        }
+
+    }
+
+    private boolean verifyArguments(List<String> args) {
+        boolean successful = true;
+        if (args.size() != 2) {
+            successful = false;
+            return successful;
+        }
+        try {
+            double singlePrice = Double.valueOf(args.get(0));
+            int quantity = Integer.valueOf(args.get(1));
+        } catch (NumberFormatException e) {
+            successful = false;
+        }
+        return successful;
+
+    }
+
+}

spring-boot/src/main/java/com/baeldung/environmentpostprocessor/PriceCalculationEnvironmentPostProcessor.java

@@ -0,0 +1,71 @@
+package com.baeldung.environmentpostprocessor;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.env.EnvironmentPostProcessor;
+import org.springframework.core.Ordered;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.MapPropertySource;
+import org.springframework.core.env.PropertySource;
+import org.springframework.core.env.StandardEnvironment;
+
+public class PriceCalculationEnvironmentPostProcessor implements EnvironmentPostProcessor, Ordered {
+
+    private static final Logger logger = LoggerFactory.getLogger(PriceCalculationEnvironmentPostProcessor.class);
+
+    public static final int DEFAULT_ORDER = Ordered.LOWEST_PRECEDENCE;
+    private int order = DEFAULT_ORDER;
+    private static final String PROPERTY_PREFIX = "com.baeldung.environmentpostprocessor.";
+    private static final String OS_ENV_PROPERTY_CALCUATION_MODE = "calculation_mode";
+    private static final String OS_ENV_PROPERTY_GROSS_CALCULATION_TAX_RATE = "gross_calculation_tax_rate";
+    private static final String OS_ENV_PROPERTY_CALCUATION_MODE_DEFAULT_VALUE = "NET";
+    private static final double OS_ENV_PROPERTY_GROSS_CALCULATION_TAX_RATE_DEFAULT_VALUE = 0;
+
+    @Override
+    public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
+
+        PropertySource<?> systemEnvironmentPropertySource = environment.getPropertySources()
+            .get(StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME);
+
+        Map<String, Object> priceCalculationConfiguration = new LinkedHashMap<>();
+        if (isActive(systemEnvironmentPropertySource)) {
+            priceCalculationConfiguration.put(key(OS_ENV_PROPERTY_CALCUATION_MODE), systemEnvironmentPropertySource.getProperty(OS_ENV_PROPERTY_CALCUATION_MODE));
+            priceCalculationConfiguration.put(key(OS_ENV_PROPERTY_GROSS_CALCULATION_TAX_RATE), systemEnvironmentPropertySource.getProperty(OS_ENV_PROPERTY_GROSS_CALCULATION_TAX_RATE));
+        } else {
+            logger.warn("System environment variables [calculation_mode,gross_calculation_tax_rate] not detected, fallback to default value [calcuation_mode={},gross_calcuation_tax_rate={}]", OS_ENV_PROPERTY_CALCUATION_MODE_DEFAULT_VALUE,
+                OS_ENV_PROPERTY_GROSS_CALCULATION_TAX_RATE_DEFAULT_VALUE);
+            priceCalculationConfiguration.put(key(OS_ENV_PROPERTY_CALCUATION_MODE), OS_ENV_PROPERTY_CALCUATION_MODE_DEFAULT_VALUE);
+            priceCalculationConfiguration.put(key(OS_ENV_PROPERTY_GROSS_CALCULATION_TAX_RATE), OS_ENV_PROPERTY_GROSS_CALCULATION_TAX_RATE_DEFAULT_VALUE);
+        }
+
+        PropertySource<?> priceCalcuationPropertySource = new MapPropertySource("priceCalcuationPS", priceCalculationConfiguration);
+        environment.getPropertySources()
+            .addAfter(StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, priceCalcuationPropertySource);
+
+    }
+
+    private String key(String key) {
+        return PROPERTY_PREFIX + key.replaceAll("\\_", ".");
+    }
+
+    private boolean isActive(PropertySource<?> systemEnvpropertySource) {
+        if (systemEnvpropertySource.containsProperty(OS_ENV_PROPERTY_CALCUATION_MODE) && systemEnvpropertySource.containsProperty(OS_ENV_PROPERTY_GROSS_CALCULATION_TAX_RATE)) {
+            return true;
+        } else
+            return false;
+    }
+
+    public void setOrder(int order) {
+        this.order = order;
+    }
+
+    @Override
+    public int getOrder() {
+        return order;
+    }
+
+}

spring-boot/src/main/java/com/baeldung/environmentpostprocessor/autoconfig/PriceCalculationAutoConfig.java

@@ -0,0 +1,32 @@
+package com.baeldung.environmentpostprocessor.autoconfig;
+
+import org.springframework.boot.autoconfigure.AutoConfigureOrder;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.Ordered;
+
+import com.baeldung.environmentpostprocessor.calculator.GrossPriceCalculator;
+import com.baeldung.environmentpostprocessor.calculator.NetPriceCalculator;
+import com.baeldung.environmentpostprocessor.calculator.PriceCalculator;
+
+@Configuration
+@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE)
+public class PriceCalculationAutoConfig {
+
+    @Bean
+    @ConditionalOnProperty(name = "com.baeldung.environmentpostprocessor.calculation.mode", havingValue = "NET")
+    @ConditionalOnMissingBean
+    public PriceCalculator getNetPriceCalculator() {
+        return new NetPriceCalculator();
+    }
+
+    @Bean
+    @ConditionalOnProperty(name = "com.baeldung.environmentpostprocessor.calculation.mode", havingValue = "GROSS")
+    @ConditionalOnMissingBean
+    public PriceCalculator getGrossPriceCalculator() {
+        return new GrossPriceCalculator();
+    }
+
+}

spring-boot/src/main/java/com/baeldung/environmentpostprocessor/calculator/GrossPriceCalculator.java

@@ -0,0 +1,23 @@
+package com.baeldung.environmentpostprocessor.calculator;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+
+public class GrossPriceCalculator implements PriceCalculator {
+
+    private static final Logger logger = LoggerFactory.getLogger(GrossPriceCalculator.class);
+
+    @Value("${com.baeldung.environmentpostprocessor.gross.calculation.tax.rate}")
+    double taxRate;
+
+    @Override
+    public double calculate(double singlePrice, int quantity) {
+        logger.info("Gross based price calculation with input parameters [singlePrice = {},quantity= {} ], {} percent tax applied.", singlePrice, quantity, taxRate * 100);
+        double netPrice = singlePrice * quantity;
+        double result = Math.round(netPrice * (1 + taxRate));
+        logger.info("Calcuation result is {}", result);
+        return result;
+    }
+
+}

spring-boot/src/main/java/com/baeldung/environmentpostprocessor/calculator/NetPriceCalculator.java

@@ -0,0 +1,17 @@
+package com.baeldung.environmentpostprocessor.calculator;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class NetPriceCalculator implements PriceCalculator {
+
+    private static final Logger logger = LoggerFactory.getLogger(GrossPriceCalculator.class);
+
+    @Override
+    public double calculate(double singlePrice, int quantity) {
+        logger.info("Net based price calculation with input parameters [singlePrice = {},quantity= {} ], NO tax applied.", singlePrice, quantity);
+        double result = Math.round(singlePrice * quantity);
+        logger.info("Calcuation result is {}", result);
+        return result;
+    }
+}

spring-boot/src/main/java/com/baeldung/environmentpostprocessor/calculator/PriceCalculator.java

@@ -0,0 +1,5 @@
+package com.baeldung.environmentpostprocessor.calculator;
+
+public interface PriceCalculator {
+    public double calculate(double singlePrice, int quantity);
+}

spring-boot/src/main/java/com/baeldung/environmentpostprocessor/service/PriceCalculationService.java

@@ -0,0 +1,17 @@
+package com.baeldung.environmentpostprocessor.service;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+import com.baeldung.environmentpostprocessor.calculator.PriceCalculator;
+
+@Service
+public class PriceCalculationService {
+
+    @Autowired
+    PriceCalculator priceCalculator;
+
+    public double productTotalPrice(double singlePrice, int quantity) {
+        return priceCalculator.calculate(singlePrice, quantity);
+    }
+}

spring-boot/src/main/resources/META-INF/spring.factories

@@ -1 +1,7 @@
 org.springframework.boot.diagnostics.FailureAnalyzer=com.baeldung.failureanalyzer.MyBeanNotOfRequiredTypeFailureAnalyzer
+org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
+com.baeldung.environmentpostprocessor.autoconfig.PriceCalculationAutoConfig
+
+org.springframework.boot.env.EnvironmentPostProcessor=\
+com.baeldung.environmentpostprocessor.PriceCalculationEnvironmentPostProcessor
+

spring-boot/src/test/java/com/baeldung/environmentpostprocessor/PriceCalculationEnvironmentPostProcessorLiveTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.environmentpostprocessor;
+
+import static org.junit.Assert.assertEquals;
+
+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.test.context.junit4.SpringRunner;
+
+import com.baeldung.environmentpostprocessor.service.PriceCalculationService;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest(classes = PriceCalculationApplication.class)
+public class PriceCalculationEnvironmentPostProcessorLiveTest {
+
+    @Autowired
+    PriceCalculationService pcService;
+
+    @Test
+    public void whenSetNetEnvironmentVariablebyDefault_thenNoTaxApplied() {
+        double total = pcService.productTotalPrice(100, 4);
+        assertEquals(400.0, total, 0);
+    }
+
+}