Java Spring中注解详解（创建Bean的对象）

秒速五厘米 2022-02-24 02:58 332阅读 0赞

### spring注解（创建Bean的对象） ###

@Controller     C: SpringMVC框架

@Service      M: service

@Repository    M: MyBatis/SpringJDBC

@Component   JavaBean不属于M或C层，并且需要通过spring创建对象

注意：依赖AOP机制的，引入aop-jar包

1、操作属性   setter   构造方法

基本类型   +  API  类           @Value（“”）不需要setter

@Component
    class Courses1 implements Courses{
        @Value("语文")
        private String name;
    
        @Override
        public String toString() {
            return "Courses1{" +
                    "name='" + name + '\'' +
                    '}';
        }
    }

2、注意Component后面可以添加id，使用方法和在config配置bean中的id的使用方法相同：

package zj.it.test;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    import zj.it.entity.Teacher;
    import zj.it.four_two.Student;
    import zj.it.twenty_seven.Hello;
    
    /**
     * Created by Jiang on 2019/3/27
     */
    public class Test {
    
        public static void main(String[] args){
            ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationConfig.xml");
          
            Couser1 student = (Couser1 ) applicationContext.getBean("stu");
            System.out.println(student);
        }
    
    }

3、如果需要使用list和map，可以直接使用@Autowired注解：

@Autowired
        @Qualifier("one")
        private Book books;

4、上面代码中的Book是一个接口， @Qualifier("one")调用的是接口的一个实现类（Qualifier用来选择要使用的类），one表示实现类的id。Book类如下：

package zj.it.four_two;
    
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.stereotype.Component;
    import org.springframework.stereotype.Service;
    
    /**
     * Created by Jiang on 2019/4/2
     */
    @Component("book")
    public interface Book {
        String setName();
    }
    @Service("one")
    class Book1 implements Book{
    
        @Value("战争中")
        private String name;
    
        public Book1() {
            System.out.println("安徒生童话");
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        @Override
        public String setName() {
            System.out.println("安徒生童话");
            return "你好";
        }
    
        @Override
        public String toString() {
            return "Book1{" +
                    "name='" + name + '\'' +
                    '}';
        }
    }
    @Service("two")
    class Book2 implements Book{
    
        @Value("战争中ssssss")
        private String name;
    
        public void setName(String name) {
            this.name = name;
        }
    
    
        public Book2() {
            System.out.println("格林童话");
        }
    
        @Override
        public String setName() {
            System.out.println("格林童话");
            return "你好啊";
        }
    
        @Override
        public String toString() {
            return "Book2{" +
                    "name='" + name + '\'' +
                    '}';
        }
    }

5、上述代码测试结果如下：

Student{name='朱江', age=22, book=[Book1{name='战争中'}, Book2{name='战争中ssssss'}], 
    bookMap={one=Book1{name='战争中'}, two=Book2{name='战争中ssssss'}}, coursesList=
    [Courses1{name='语文'}, Courses1{name='数学'}, Courses1{name='英语'}, Courses1{name='物理'}, 
    Courses1{name='化学'}], books=Book1{name='战争中'}, stringSet=[sssss, sssseweerss], 
    booksLength=[Book1{name='吱吱吱吱1'}, Book2{name='吱吱吱吱2'}, Book1{name='吱吱吱吱3'}, 
    Book2{name='吱吱吱吱4'}], classRooms=ClassRooms{name='一班'}, teachers=Teachers{yid=111111,
     name='朱江水水水水'}}

6、完整Student类代码如下：

package zj.it.four_two;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.beans.factory.annotation.Qualifier;
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.stereotype.Component;
    import zj.it.entity.ClassRoom;
    
    import java.util.Arrays;
    import java.util.List;
    import java.util.Map;
    import java.util.Set;
    
    /**
     * Created by Jiang on 2019/4/2
     */
    @Component("stu")
    public class Student {
    
        @Value("朱江")
        private String name;
        @Value("22")
        private int age;
        private List<Book> book;
        private Map<String, Book> bookMap;
        private List<Courses> coursesList;
        @Autowired
        @Qualifier("one")
        private Book books;
    
        private Set<String> stringSet;
    
        private Book[] booksLength;
        private ClassRooms classRooms;
        private Teachers teachers;
    
    
        public Student() {
        }
    
        @Autowired()
        public Student(List<Book> book, Map<String, Book> bookMap,Teachers teachers,ClassRooms classRooms,List<Courses> coursesList) {
            this.book = book;
            this.bookMap = bookMap;
            this.teachers = teachers;
            this.classRooms = classRooms;
            this.coursesList = coursesList;
        }
    
        public void setBooksLength(Book[] booksLength) {
            this.booksLength = booksLength;
        }
    
        public void setStringSet(Set<String> stringSet) {
            this.stringSet = stringSet;
        }
    
        @Override
        public String toString() {
            return "Student{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    ", book=" + book +
                    ", bookMap=" + bookMap +
                    ", coursesList=" + coursesList +
                    ", books=" + books +
                    ", stringSet=" + stringSet +
                    ", booksLength=" + Arrays.toString(booksLength) +
                    ", classRooms=" + classRooms +
                    ", teachers=" + teachers +
                    '}';
        }
    }

先说到这，有补充欢迎留言。