Spring @Autowired注解用在集合上面，可以保持接口的所有實現類

CourseService課程接口有2個子類，HistroyCourseServiceImpl和MathsCourseServiceImpl

public interface CourseService {

    String getCourseName();

    void attendCourse();
}

package com.junge.spring.demo.service.course.impl;

import com.junge.spring.demo.service.course.CourseService;
import org.springframework.stereotype.Service;

import java.util.logging.Logger;

/**
 * 歷史課
 *
 * @author liuxj
 * @create 2018-01-06 12:46
 */
@Service
public class HistroyCourseServiceImpl implements CourseService {

    private static final Logger logger = Logger.getLogger(HistroyCourseServiceImpl.class.getName());

    @Override
    public String getCourseName() {
        return "歷史";
    }

    @Override
    public void attendCourse() {
        System.out.println("上歷史課");
        logger.info("上歷史課");
    }
}

package com.junge.spring.demo.service.course.impl;

import com.junge.spring.demo.service.course.CourseService;
import org.springframework.stereotype.Service;

import java.util.logging.Logger;

/**
 * 數學課
 *
 * @author liuxj
 * @create 2018-01-06 12:49
 */
@Service
public class MathsCourseServiceImpl implements CourseService {
    private static final Logger logger = Logger.getLogger(MathsCourseServiceImpl.class.getName());

    @Override
    public String getCourseName() {
        return "數學課";
    }

    @Override
    public void attendCourse() {
        System.out.println("上數學課");
        logger.info("上數學課");
    }
}

學生類有接口attendAllCourse，參加所有課程

public interface StudentService {

    void addStudent();

    Student getStudent(int id);

    void updateStudent(Student student);

    void attendAllCourse(Student student);
}

package com.junge.spring.demo.service.impl;

import com.junge.spring.demo.model.Student;
import com.junge.spring.demo.service.StudentService;
import com.junge.spring.demo.service.course.CourseService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.util.CollectionUtils;

import java.util.Set;
import java.util.logging.Logger;

/**
 * 業務實現類
 *
 * @author liuxj
 * @create 2018-01-06 11:24
 */
@Service
public class StudentServiceImpl implements StudentService {

    private static final Logger logger = Logger.getLogger(StudentServiceImpl.class.getName());

    /** * @Autowired注解用在集合上面，可以保持接口的所有實現類 */ @Autowired private Set<CourseService> courseSet;

    @Override
    public void addStudent() {
        System.out.println("addStudent");
        logger.info("addStudent");
    }

    @Override
    public Student getStudent(int id) {

        System.out.println("getStudent id=" + id);
        logger.info("getStudent id=" + id);

        Student student = new Student();
        student.setId(id);
        student.setAge(22);
        student.setName("張勝男");
        return student;
    }

    @Override
    public void updateStudent(Student student) {
        System.out.println("updateStudent info:" + student);
        logger.info("updateStudent info:" + student);
    }

    @Override
    public void attendAllCourse(Student student) { if (!CollectionUtils.isEmpty(courseSet)) { for (CourseService service : courseSet) { service.attendCourse(); } } }
}

調用學生上課接口，可以打印所有課程，說明CourseService所有的實現類都注冊到集合courseSet