single table inheritance

hibernate-inheritance2/pom.xml

@@ -0,0 +1,61 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<groupId>org.springframework.boot</groupId>
+		<artifactId>spring-boot-starter-parent</artifactId>
+		<version>2.3.3.RELEASE</version>
+		<relativePath/> <!-- lookup parent from repository -->
+	</parent>
+	<groupId>ru.sysout</groupId>
+	<artifactId>inherit2</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<name>inherit2</name>
+
+	<properties>
+		<java.version>11</java.version>
+	</properties>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-data-jpa</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>com.h2database</groupId>
+			<artifactId>h2</artifactId>
+			<scope>runtime</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.projectlombok</groupId>
+			<artifactId>lombok</artifactId>
+			<optional>true</optional>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-web</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-test</artifactId>
+			<scope>test</scope>
+			<exclusions>
+				<exclusion>
+					<groupId>org.junit.vintage</groupId>
+					<artifactId>junit-vintage-engine</artifactId>
+				</exclusion>
+			</exclusions>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+			</plugin>
+		</plugins>
+	</build>
+
+</project>

hibernate-inheritance2/src/main/java/ru/sysout/SpringDataJpaApplication.java

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+package ru.sysout;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class SpringDataJpaApplication  {
+    public static void main(String[] args) {
+        SpringApplication.run(SpringDataJpaApplication.class, args);
+    }
+
+}

hibernate-inheritance2/src/main/java/ru/sysout/dao/CustomerRepository.java

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+package ru.sysout.dao;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import ru.sysout.model.Customer;
+
+public interface CustomerRepository extends JpaRepository<Customer, Long> {
+
+}

hibernate-inheritance2/src/main/java/ru/sysout/model/Customer.java

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+package ru.sysout.model;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.*;
+
+@Data
+@NoArgsConstructor
+@Entity
+@Inheritance
+public class Customer {
+    @Id
+    @GeneratedValue(strategy = GenerationType.SEQUENCE)
+    private long id;
+    private String name;
+}

hibernate-inheritance2/src/main/java/ru/sysout/model/EmployeeCustomer.java

@@ -0,0 +1,11 @@
+package ru.sysout.model;
+
+import lombok.Data;
+
+import javax.persistence.Entity;
+
+@Data
+@Entity
+public class EmployeeCustomer extends Customer {
+    private int monthsInCompany;
+}

hibernate-inheritance2/src/main/java/ru/sysout/model/ExternalCustomer.java

@@ -0,0 +1,11 @@
+package ru.sysout.model;
+
+import lombok.Data;
+
+import javax.persistence.Entity;
+
+@Data
+@Entity
+public class ExternalCustomer extends Customer {
+   private long sum;
+}

hibernate-inheritance2/src/main/java/ru/sysout/service/DiscountCalculator.java

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+package ru.sysout.service;
+
+public interface DiscountCalculator<T> {
+    double calculate(T customer);
+    Class<T> getClazz();
+}

hibernate-inheritance2/src/main/java/ru/sysout/service/EmployeeCustomerDiscountCalculator.java

@@ -0,0 +1,18 @@
+package ru.sysout.service;
+
+import org.springframework.stereotype.Service;
+import ru.sysout.model.EmployeeCustomer;
+
+@Service
+public class EmployeeCustomerDiscountCalculator implements DiscountCalculator<EmployeeCustomer> {
+    @Override
+    public double calculate(EmployeeCustomer customer) {
+        if (customer.getMonthsInCompany() > 12)
+            return 0.1;
+        return 0.05;
+    }
+
+    public Class getClazz(){
+        return EmployeeCustomer.class;
+    }
+}

hibernate-inheritance2/src/main/java/ru/sysout/service/ExternalCustomerDiscountCalculator.java

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+package ru.sysout.service;
+
+import org.springframework.stereotype.Service;
+import ru.sysout.model.ExternalCustomer;
+
+@Service
+public class ExternalCustomerDiscountCalculator implements DiscountCalculator<ExternalCustomer> {
+    @Override
+    public double calculate(ExternalCustomer customer) {
+        if (customer.getSum() > 100)
+            return 0.01;
+        return 0.05;
+    }
+    public Class getClazz(){
+        return ExternalCustomer.class;
+    }
+}

hibernate-inheritance2/src/main/java/ru/sysout/service/MakeDiscountsService.java

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+package ru.sysout.service;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+import ru.sysout.dao.CustomerRepository;
+import ru.sysout.model.Customer;
+
+import javax.annotation.PostConstruct;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+@Service
+public class MakeDiscountsService {
+    @Autowired
+    private CustomerRepository customerRepository;
+    @Autowired
+    private List<DiscountCalculator> calculators;
+
+    private Map<Class, DiscountCalculator> map = new HashMap<>();
+
+    @PostConstruct
+    private void init() {
+        for (DiscountCalculator discountCalculator : calculators) {
+            map.put(discountCalculator.getClazz(), discountCalculator);
+        }
+    }
+
+    public void makeDiscounts() {
+        List<Customer> customers = customerRepository.findAll();
+        for (Customer customer : customers) {
+            DiscountCalculator discountCalculator = map.get(customer.getClass());
+            double discount = discountCalculator.calculate(customer);
+            System.out.println(discount);
+        }
+    }
+}
+

hibernate-inheritance2/src/main/resources/application.yml

@@ -0,0 +1,14 @@
+spring:
+  h2:
+    console:
+      enabled: true
+      path: /h2-console
+  datasource:
+     url: jdbc:h2:mem:testdb
+     username: sa
+     password:
+     initialization-mode: never
+  jpa:
+    show-sql: true
+    hibernate:
+      ddl-auto: create

hibernate-inheritance2/src/test/java/ru/sysout/CustomerCalculatorTest.java

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+package ru.sysout;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
+import org.springframework.context.annotation.Import;
+import ru.sysout.dao.CustomerRepository;
+import ru.sysout.model.EmployeeCustomer;
+import ru.sysout.model.ExternalCustomer;
+import ru.sysout.service.EmployeeCustomerDiscountCalculator;
+import ru.sysout.service.ExternalCustomerDiscountCalculator;
+import ru.sysout.service.MakeDiscountsService;
+
+@DataJpaTest
+@Import({MakeDiscountsService.class, EmployeeCustomerDiscountCalculator.class, ExternalCustomerDiscountCalculator.class})
+public class CustomerCalculatorTest {
+    @Autowired
+    private CustomerRepository customerRepository;
+
+    @Autowired
+    private MakeDiscountsService makeDiscountsService;
+
+    @BeforeEach
+    private void init() {
+        EmployeeCustomer employeeCustomer = new EmployeeCustomer();
+        employeeCustomer.setMonthsInCompany(10);
+        employeeCustomer.setName("Petr");
+        customerRepository.save(employeeCustomer);
+
+        ExternalCustomer externalCustomer = new ExternalCustomer();
+        externalCustomer.setSum(110);
+        externalCustomer.setName("Vasya");
+        customerRepository.save(externalCustomer);
+    }
+
+    @Test
+    public void test() {
+        makeDiscountsService.makeDiscounts();
+    }
+}