Add student service

src/main/java/com/example/demo/lesson20/entity/Student.java

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+package com.example.demo.lesson20.entity;
+
+public class Student {
+
+	private String id;
+	private String name;
+	private Integer age;
+
+	public Student() {
+	}
+	public Student(String id, String name, Integer age) {
+		super();
+		this.id = id;
+		this.name = name;
+		this.age = age;
+	}
+	public String getId() {
+		return id;
+	}
+	public void setId(String id) {
+		this.id = id;
+	}
+	public String getName() {
+		return name;
+	}
+	public void setName(String name) {
+		this.name = name;
+	}
+	public Integer getAge() {
+		return age;
+	}
+	public void setAge(Integer age) {
+		this.age = age;
+	}
+	@Override
+	public String toString() {
+		return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
+	}
+
+}

src/main/java/com/example/demo/lesson20/service/StudentService.java

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+package com.example.demo.lesson20.service;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.springframework.stereotype.Service;
+
+import com.example.demo.lesson20.entity.Student;
+
+@Service
+public class StudentService {
+
+	static Map<String, Student> students = new HashMap<>();
+
+	static {
+		students.put("11", new Student("11", "Tom", 23));
+		students.put("12", new Student("12", "Jerry", 25));
+		students.put("13", new Student("13", "David", 32));
+		students.put("14", new Student("14", "Jack", 41));
+	}
+
+	public Student findById(String id) {
+		return students.get(id);
+	}
+
+	public List<Student> findAll() {
+		return new ArrayList<Student>(students.values());
+	}
+
+}

src/main/java/com/example/demo/lesson20/web/StudentController.java

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+package com.example.demo.lesson20.web;
+
+import java.util.List;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.http.MediaType;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import com.example.demo.lesson20.entity.Student;
+import com.example.demo.lesson20.service.StudentService;
+
+@RestController
+@RequestMapping("/student")
+public class StudentController {
+
+	@Autowired
+	private StudentService studentService;
+
+	@GetMapping(value="/id1")
+	public Student findById(String id) {
+		return studentService.findById(id);
+	}
+
+	@GetMapping(value="/id2", produces=MediaType.APPLICATION_XML_VALUE)
+	public Student findById2(String id) {
+		return studentService.findById(id);
+	}
+
+	@GetMapping(value="/list1")
+	public List<Student> findAll(){
+		return studentService.findAll();
+	}
+
+	@GetMapping(value="/list2", produces=MediaType.APPLICATION_JSON_VALUE)
+	public List<Student> findAll2(){
+
+		return studentService.findAll();
+	}
+}