diagram

pom.xml

<?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>2.3.1.RELEASE</version>
 <relativePath/> <!-- lookup parent from repository -->
 </parent>
 <groupId>com.example</groupId>
 <artifactId>demo</artifactId>
 <version>0.0.1-SNAPSHOT</version>
 <name>demo</name>
 <description>Demo project for Spring Boot</description>
 <properties>
 <java.version>1.8</java.version>
 <powermock.version>2.0.7</powermock.version>
 </properties>
 <dependencies>
 <dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-web</artifactId>
 </dependency>
 <dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-devtools</artifactId>
 <scope>runtime</scope>
 <optional>true</optional>
 </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>
 <dependency>
 <groupId>org.junit.platform</groupId>
 <artifactId>junit-platform-launcher</artifactId>
 <scope>test</scope>
 </dependency>
 </dependencies>
 <build>
 <plugins>
 <plugin>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-maven-plugin</artifactId>
 </plugin>
 </plugins>
 </build>
</project>

1 OperationService.java

package com.example.demo.service;
public interface OperationService {
 Double operate(Double a, Double b);
}

2 AddOperationServiceImpl.java

package com.example.demo.service.impl;
import com.example.demo.service.OperationService;
import org.springframework.stereotype.Service;
@Service("addOperationService")
public class AddOperationServiceImpl implements OperationService{
 @Override
 public Double operate(Double a, Double b) {
 return a+b;
 }
}

3 TimesOperationServiceImpl.java

package com.example.demo.service.impl;
import com.example.demo.service.OperationService;
import org.springframework.stereotype.Service;
@Service("timesOperationService")
public class TimesOperationServiceImpl implements OperationService {
 @Override
 public Double operate(Double a, Double b) {
 return a * b;
 }
}

4 OperationEnum.java

package com.example.demo.enums;
import java.util.HashMap;
import java.util.Map;
public enum OperationEnum {
 ADD("ADD", "addOperationService"),
 TIMES("TIMES", "timesOperationService")
 ;
 public final String operation;
 public final String operationServiceName;
 private static Map<String, OperationEnum> map = new HashMap<>();
 OperationEnum(String operation, String operationServiceName) {
 this.operation = operation;
 this.operationServiceName = operationServiceName;
 }
 static {
 for(OperationEnum e : OperationEnum.values()){
 map.put(e.name(), e);
 }
 }
 public static OperationEnum get(final String operation) {
 OperationEnum e = map.get(operation);
 if (e == null){
 throw new IllegalArgumentException( "MSG:M070");
 }
 return e;
 }
}

5 OperationStrategyContextFactory.java

package com.example.demo.context;
import com.example.demo.enums.OperationEnum;
import com.example.demo.service.OperationService;
public interface OperationStrategyContextFactory {
 OperationService get(OperationEnum e);
 OperationService get(String operation);
}

6 OperationStrategyContextFactoryImpl.java

package com.example.demo.context.impl;
import com.example.demo.enums.OperationEnum;
import com.example.demo.context.OperationStrategyContextFactory;
import com.example.demo.service.OperationService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import java.util.HashMap;
import java.util.Map;
@Component
public class OperationStrategyContextFactoryImpl implements OperationStrategyContextFactory {
 @Autowired 
 private Map<String, OperationService> operationServices = new HashMap<>();
 @Override
 public OperationService get(OperationEnum e) {
 return operationServices.get(e.operationServiceName);
 }
 @Override
 public OperationService get(String operation) {
 return operationServices.get(OperationEnum.get(operation).operationServiceName);
 }
}

7 Junit Test DemoApplicationTests.java

package com.example.demo;
import com.example.demo.context.OperationStrategyContextFactory;
import com.example.demo.enums.OperationEnum;
import com.example.demo.service.OperationService;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
@SpringBootTest
public class DemoApplicationTests {
 @Autowired
 OperationStrategyContextFactory operationStrategyContextFactory;
 @Test
 void contextLoads() {
 }
 @Test
 public void add(){
 Double a = 100d;
 Double b = 200d;
 OperationService operationService = operationStrategyContextFactory.get(OperationEnum.ADD);
 OperationService operationService1 = operationStrategyContextFactory.get("ADD");
 Double c = operationService.operate(a, b);
 Double c1 = operationService1.operate(a, b);
 Assertions.assertEquals(300d, c);
 Assertions.assertEquals(300d, c1);
 }
 @Test
 public void times(){
 Double a = 100d;
 Double b = 200d;
 OperationService operationService = operationStrategyContextFactory.get(OperationEnum.TIMES);
 OperationService operationService1 = operationStrategyContextFactory.get("TIMES");
 Double c = operationService.operate(a, b);
 Double c1 = operationService1.operate(a, b);
 Assertions.assertEquals(20000d, c);
 Assertions.assertEquals(20000d, c1);
 }
}

8 TestController.java

package com.example.demo.controller;
import com.example.demo.enums.OperationEnum;
import com.example.demo.context.OperationStrategyContextFactory;
import com.example.demo.service.OperationService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class TestController {
 @Autowired
 OperationStrategyContextFactory operationStrategyContextFactory;
 @RequestMapping("add")
 public Double add(){
 Double a = 100d;
 Double b = 200d;
 OperationService operationService = operationStrategyContextFactory.get(OperationEnum.ADD);
 OperationService operationService1 = operationStrategyContextFactory.get("ADD");
 Double c = operationService.operate(a, b);
 Double c1 = operationService1.operate(a, b);
 System.out.println(c);
 System.out.println(c1);
 return c;
 }
 @RequestMapping("times")
 public Double times(){
 Double a = 100d;
 Double b = 200d;
 OperationService operationService = operationStrategyContextFactory.get(OperationEnum.TIMES);
 OperationService operationService1 = operationStrategyContextFactory.get("TIMES");
 Double c = operationService.operate(a, b);
 Double c1 = operationService1.operate(a, b);
 System.out.println(c);
 System.out.println(c1);
 return c;
 }
}

小结