Spring创建对象的几种方法

一、通过构造器

 

无参构造器

<?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">

<!--配置我们的Dog类  spring 框架在底层 
  通过反射的机制  执行了我们的构造方法-->
<bean id="dog" class="cn.pb.dao.impl.Dog"></bean>


</beans>

直接这样配置一个bean的话，相当于是调用这个Dog类的无参构造器，如果无参构造器不在，Spring上下文创建对象的时候就会报错。

 

 

无参构造器加setter方法注入field的值

类：

package com.mc.base.learn.spring.bean;

public class Person {

    private String name;
    private Integer id;
    
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    @Override
    public String toString() {
        return "Person [name=" + name + ", >;
    }

}

 

bean配置：

<?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">

    <bean class="com.mc.base.learn.spring.bean.Person" >
        <property name="name" value="LiuChunfu"></property>
        <property name="id" value="125"></property>
    </bean>
    
</beans>

就bean标签下再用property标签来设置name和value

 

如果有field是引用型的，就不用value，用ref = "xxx"，xxx就是某个bean的id或者name

 

 

利用有参数的构造方法：

类代码：

package com.mc.base.learn.spring.bean;

public class Person {

    private String name;
    private Integer id;
    
    public Person(String name, Integer id) {
        super();
        this.name = name;
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    @Override
    public String toString() {
        return "Person [name=" + name + ", >;
    }

}

View Code