用@AutoWired和@Resource自动装配Bean

1.@AutoWired和@Resource介绍

　　Spring的主配置文件如下

@AutoWired

　　@AutoWired只有一个属性：required boolean 类型该值默认是true ，

　　它会从你的配置文件中寻找类型一致或者类型存在继承，实现的关系的bean

　　如果required=true，找不到就报异常，required=false 找不到就不注入了

　　@AutoWired 的定义

从定义上看这个注解可以作用在构造函数上，字段上，方法上，注解上（注解上我不知道怎么用）

实体类Student

package ls.entity;/** * 学生类 * @author liusheng */public class Student {    /**     * 学号     */    private String Student_ID;    /**     * 名字     */    private String name;    /**     * 年龄     */    private  int age;    public String getStudent_ID() {        return Student_ID;    }    public void setStudent_ID(String student_ID) {        Student_ID = student_ID;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    public String toString() {        return "Student [Student_ID=" + Student_ID + ", name=" + name + ", age=" + age + "]";    }}

　实体类 User

package ls.entity;/** * User class * @author liusheng */public class User {    /**     * name     */        private String name;        /**         * age         */        private Integer age;        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;        }        public String toString() {            return "User [name=" + name + ", age=" + age + "]";        }}

字段上

package liusheng.springboot.Spring;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;import ls.entity.Student;@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration("classpath:applicationContext.xml")public class AotuWiredTest  {        @Autowired        Student student;        @Test        public void test1() throws Exception {            System.out.println(student);        }}

因为在字段上，所以不需要set方法，通过反射对属性直接赋值

通过方法赋值（注意：这个方法不一定是setStudent(Student student) ,还可以是setaa(Student student);）

package liusheng.springboot.Spring;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;import ls.entity.Student;@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration("classpath:applicationContext.xml")public class AotuWiredTest  {        Student student;        @Test                public void test1() throws Exception {            System.out.println(student);        }        @Autowired        public void setStudent(Student student) {            this.student = student;        }}

通过构造方法赋值（注意：要保留无参构造函数）

package liusheng.springboot.Spring;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Component;import ls.entity.Student;@Componentpublic class ConstuctorWired {        private Student student;        public Student getStudent() {            return student;        }                public ConstuctorWired() {        }        @Autowired        public ConstuctorWired(Student student) {            this.student = student;        }        public String toString() {            return "constuctorWired [student=" + student + "]";        }        public void setStudent(Student student) {            this.student = student;        }        }

package liusheng.springboot.Spring;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;import ls.entity.Student;@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration("classpath:applicationContext.xml")public class AotuWiredTest  {        @Autowired        ConstuctorWired c;                @Test        public void test1() throws Exception {            System.out.println(c);        }                public AotuWiredTest() {        }        }

@Resource

该注解可以用在方法上和字段上

如果不写name属性那么按照类型注入，如果指定的name 属性那么就按name注入

package liusheng.springboot.Spring;import javax.annotation.Resource;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;import ls.entity.User;@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration("classpath:applicationContext.xml")public class ResourceAutoWired {        @Resource()        private User user;                private User user1;        @Resource(name="user")        private User user2;        @Resource(name="user")        public void setUser1(User user1) {            this.user1 = user1;        }        @Test        public void test() throws Exception {            System.out.println("有name属性在方法上"+user1);            System.out.println("有name属性在字段上"+user2);            System.out.println("没有name属性"+user);        }}

console输出：