ioc - 设置注入概念 - 《SSM学习笔记》

怎么给一个对象的属性给属性赋值
- 基于XML的DI(理解，用的比较少)
- 基于注解的DI(掌握)

一个java对象肯定有属性方法

怎么给一个对象的属性给属性赋值

在spring配置文件中，给java对象的属性赋值

**di:依赖注入**,表示创建对象给属性赋值

di的实现语法有俩种

di的语法分类:

set注入(设置注入): spring调用类的set方法，在set方法中可以实现属性的赋值
- 80%左右都是使用set注入
构造注入,spring调用类的有参数构造方法，创建对象。在构造方法中完成赋值

public class Student {
    private Integer id;
    private String name;
    private int age;
    public Student() {
    }
    public Student(Integer id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = 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;
    }
    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

基于XML的DI(理解，用的比较少)

我们在spring的配置开发中有默认的配置名称(选择的是spring config创建):applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    <!--声明student对象-->
    <bean id="myStudent" class="org.chentianyu.users.Student" />
</beans>

xml文件修改(applicationContext.xml)

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    <!--
        声明student对象
        注入: 就是赋值的意思
        简单类型: spring中规定java的基本类型和String字符串都是简单类型
        di: 给属性赋值
        1.set注入(设置注入): spring调用类的set方法,你可以在set方法中完成属性赋值
        1)简单类型的set注入
            <bean id="xx" class="yyy">
                <property name="属性名字" value="属性的值" />
                一个property只能给一个属性赋值
                <property name="属性名字" value="属性的值" 
            </bean>
    -->
    <bean id="myStudent" class="org.chentianyu.users.Student" >
        <property name="name" value="李四" />
        <property name="age" value="20" />
        <property name="id" value="1" />
    </bean>
</beans>

若是把applicationContext.xml放在resources目录下的一个名叫chen的目录下,config路径得是String config = "chen/applicationContext.xml";

这个是基于对象的set方法来传参的如果我们去除了setName方法的话

Bean property 'name' is not writable or has an invalid setter method. Did you mean 'age'?

User中的name属性没有setter方法

设值注入只有使用set方法

如果写一个不存在参数的setter方法

public void setEmail(String email){
    System.out.println("setEmail="+email);
}

<bean id="myStudent" class="org.chentianyu.users.Student" >
    <property name="name" value="李四" /><!--setName("李四")-->
    <property name="age" value="20" /><!--setAge(20)-->
    <property name="id" value="1" /><!--setId(1)-->
    <property name="email" value="123@qq.com" />
</bean>

@Test
public void test05(){
    String config = "chen/applicationContext.xml";
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext(config);

    //从容器中获取Student对象
    Student myStudent = (Student) applicationContext.getBean("myStudent");
    System.out.println("Student对象=" + myStudent);
}

setEmail=123@qq.com
Student对象=Student{id=1, name='李四', age=20}

引用类型的设值注入

编写一个School.java

package org.chentianyu.ba02;public class School {    private String name;    private String address;    public School() {    }    public School(String name, String address) {        this.name = name;        this.address = address;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getAddress() {        return address;    }    public void setAddress(String address) {        this.address = address;    }    @Override    public String toString() {        return "School{" +                "name='" + name + '\'' +                ", address='" + address + '\'' +                '}';    }}

在Student.java类中引用

package org.chentianyu.users;import org.chentianyu.ba02.School;public class Student {    private Integer id;    private String name;    private int age;        private School school;    public Student() {    }    public Student(Integer id, String name, int age) {        this.id = id;        this.name = name;        this.age = age;    }    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = 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 void setEmail(String email){        System.out.println("setEmail="+email);    }    public School getSchool() {        return school;    }    public void setSchool(School school) {        this.school = school;    }    @Override    public String toString() {        return "Student{" +                "id=" + id +                ", name='" + name + '\'' +                ", age=" + age +                ", school=" + school +                '}';    }}

那我要创建Student类怎么做?

先新建一个测试类

package org.chentianyu;import org.chentianyu.ba02.School;import org.chentianyu.users.Student;import org.junit.Test;public class AppTest02 {    @Test    public void testSpringStudent(){        //手动创建        Student student = new Student();        student.setName("李四");        student.setAge(20);        School school = new School();        school.setName("杭州职业技术学院");        school.setAddress("杭州下沙");        student.setSchool(school);        System.out.println(student);    }}

运行结果

Student{id=null, name='李四', age=20, school=School{name='杭州职业技术学院', address='杭州下沙'}}

beans.xml(Spring Config)

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">    ....    <!--        引用类型的注入: set调用类的set方法        <bean id="xxx" class="yyy" >            <property name="属性名称" ref="bean的id(bean对象的名称)" />        </bean>    -->    <bean id="myStudent" class="org.chentianyu.ba02.Student">        <property name="name" value="李四" />        <property name="age" value="22" />        <!--引用类型-->        <property name="school" ref="mySchool" />    </bean>    <!--声明School对象-->    <bean id="mySchool" class="org.chentianyu.ba02.School">        <property name="name" value="杭州职业技术学院" />        <property name="address" value="杭州下沙" />    </bean></beans>

@Testpublic void testSpringStudent(){    String config = "chen/applicationContext.xml";    ApplicationContext applicationContext = new ClassPathXmlApplicationContext(config);    Student myStudent = (Student) applicationContext.getBean("myStudent");    System.out.println(myStudent);}

构造注入

package org.chentianyu.ba02;public class Student {    private Integer id;    private String name;    private int age;    private School school;    public Student() {        System.out.println("无参构造方法执行了");    }    public Student(Integer id, String name, int age) {        System.out.println("有参构造方法执行了");        this.id = id;        this.name = name;        this.age = age;    }    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = 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 void setEmail(String email){        System.out.println("setEmail="+email);    }    public School getSchool() {        return school;    }    public void setSchool(School school) {        this.school = school;    }    @Override    public String toString() {        return "Student{" +                "id=" + id +                ", name='" + name + '\'' +                ", age=" + age +                ", school=" + school +                '}';    }}

bean01>applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">    <!--    构造注入: spring调用类有参数的构造方法，在创建的同时，在构造方法中给属性赋值    构造注入使用的是:<constructor-arg>标签    <constructor-arg>标签: 一个<constructor-arg>表示一个构造方法一个参数        name: 表示构造方法的形参名        index: 表示构造方法的参数位置,参数从左到右位置是0,1,2的顺序        value: 如果构造方法的形参类型是简单类型，使用value;        ref: 构造方法的形参类型是引用数据类型,使用ref    -->    <bean id="myStudent" class="org.chentianyu.ba02.Student">        <constructor-arg name="id" index="0" value="3" />        <constructor-arg name="name" index="1" value="我" />        <constructor-arg name="age" index="2" value="20" />        <constructor-arg name="school" index="3" ref="mySchool" />    </bean>    <bean id="mySchool" class="org.chentianyu.ba02.School">        <property name="name" value="杭州职业技术学院" />        <property name="address" value="杭州下沙" />    </bean></beans>

AppTest02.java

@Testpublic void  testGZ(){    String config = "bean01/applicationContext.xml";    ApplicationContext applicationContext =        new ClassPathXmlApplicationContext(config);    Student myStudent = (Student) applicationContext.getBean("myStudent");    System.out.println(myStudent);}

基于注解的DI(掌握)

请看**注解**栏