Spring之IOC之sping-context实现立即加载

通过之前的学习使用BeanFactory通过延迟加载实现了全部对象的创建并存储到了容器map中

今天学习SpringIOC的spring-context如何实现立即加载!

预习:

需要引入依赖:spring-context
bean标签的解释:
- ①id:从容器中准确取出对象的唯一标识,接口类文件名(开头字母小写)
- ②class:所要创建对象的实现类全路径
- ③scope:代表创建对象的范围:
  - 1>singleton:default 单例模式:即全局使用的都是同一个对象后期对象由Spring维护(生存&销毁)
    - 创建出来的对象地址全部一致
  - 2>prototype:多例模式:需要时就创建一个新的对象,不保证唯一后期对象不由Spring维护
    - 创建出来的对象的地址有可能不一致
生命周期:
- init-method:对象创建之后执行的方法
- destroy-method:对象销毁之前执行的方法

一.案例展示

1.测试准备

项目准备:

2.代码展示:

***pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.howie</groupId>
    <artifactId>springIOC_eager_load</artifactId>
    <version>1.0-SNAPSHOT</version>
    
    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>
        <!--单元测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <!--spring-context-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.1.8.RELEASE</version>
        </dependency>
    </dependencies>
</project>

***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">
    <!--配置对象创建信息-->
    <bean id="accountDao" class="com.howie.dao.impl.AccountDaoImpl"
          init-method="initShow" destroy-method="destoryShow"
          scope="singleton"
    />
    <bean id="accountService" class="com.howie.service.impl.AccountServiceImpl"
          init-method="initShow" destroy-method="destoryShow"
          scope="prototype"
    />
</beans>

***Account.java

package com.howie.pojo;

/**
 * @Author weihuanwen
 * @Date 2019/8/13 21:53
 * @Version 1.0
 */
public class Account {
    private String id;
    private String accountName;
    private double money;

    public String getId() {
        return id;
    }

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

    public String getAccountName() {
        return accountName;
    }

    public void setAccountName(String accountName) {
        this.accountName = accountName;
    }

    public double getMoney() {
        return money;
    }

    public void setMoney(double money) {
        this.money = money;
    }

    @Override
    public String toString() {
        return "Account{" +
                "id='" + id + '\'' +
                ", accountName='" + accountName + '\'' +
                ", money=" + money +
                '}';
    }
}

***AccountDao.java

package com.howie.dao;

import com.howie.pojo.Account;

/**
 * @Author weihuanwen
 * @Date 2019/8/13 22:09
 * @Version 1.0
 */
public interface AccountDao {
    /**
     * 保存账户信息
     * @param account
     */
    void saveAccount(Account account);
}

***AccountDaoImpl.java

package com.howie.dao.impl;

import com.howie.dao.AccountDao;
import com.howie.pojo.Account;

/**
 * @Author weihuanwen
 * @Date 2019/8/13 22:09
 * @Version 1.0
 */
public class AccountDaoImpl implements AccountDao {

    /**
     * 为了观察生命周期,在空参构造中加入提示信息
     */
    public AccountDaoImpl() {
        System.out.println("调用了AccountDaoImpl的空参构造创建对象!");
    }

    public void initShow(){
        System.out.println("AccountDaoImpl对象创建成功!");
    }
    public void destoryShow(){
        System.out.println("AccountDaoImpl对象即将被销毁!");
    }
    /**
     * 保存账户信息
     * 模拟保存数据至数据库的操作
     * @param account
     */
    public void saveAccount(Account account) {
        System.out.println(account);
        System.out.println("账户信息保存成功!");
    }
}

***AccountService.java

package com.howie.service;

import com.howie.pojo.Account;

/**
 * @Author weihuanwen
 * @Date 2019/8/13 21:54
 * @Version 1.0
 */
public interface AccountService {

    /**
     * 保存账户信息
     * @param account
     */
    void saveAccount(Account account);
}

***AccountServiceImpl.java

package com.howie.service.impl;

import com.howie.dao.AccountDao;
import com.howie.pojo.Account;
import com.howie.service.AccountService;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @Author weihuanwen
 * @Date 2019/8/13 21:54
 * @Version 1.0
 */
public class AccountServiceImpl implements AccountService {

    private AccountDao accountDao;
    /**
     * 为了观察生命周期,在空参构造中加入提示信息
     */
    public AccountServiceImpl() {
        //获取spring容器对象
        ClassPathXmlApplicationContext context =
                new ClassPathXmlApplicationContext("ApplicationContext.xml");
        this.accountDao = context.getBean("accountDao",AccountDao.class);
        System.out.println("调用了AccountServiceImpl的空参构造创建对象!");
    }

    public void initShow(){
        System.out.println("AccountServiceImpl对象创建成功!");
    }
    public void destoryShow(){
        System.out.println("AccountServiceImpl对象即将被销毁!");
    }
    /**
     * 保存用户信息
     * @param account
     */
    @Override
    public void saveAccount(Account account) {
        accountDao.saveAccount(account);
    }
}

***AccountTest.java

package com.howie.controller;

import com.howie.dao.AccountDao;
import com.howie.pojo.Account;
import com.howie.service.AccountService;
import org.junit.Test;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * @Author weihuanwen
 * @Date 2019/8/13 22:21
 * @Version 1.0
 */
public class AccountTest {

    /**
     * 保存账户
     */
    @Test
    public void saveAccount(){
        ClassPathXmlApplicationContext context =
                new ClassPathXmlApplicationContext("ApplicationContext.xml");
        AccountService accountService = context.getBean("accountService", AccountService.class);
        Account account = new Account();
        account.setId("2");
        account.setAccountName("Lily");
        account.setMoney(1000);
        accountService.saveAccount(account);
    }


    /**
     * 测试多例模式
     */
    @Test
    public void testScope(){
        ClassPathXmlApplicationContext context =
                new ClassPathXmlApplicationContext("ApplicationContext.xml");
        AccountService accountService1 = context.getBean("accountService", AccountService.class);
        System.out.println("accountService1 ::: "+accountService1);
        AccountDao accountDao1 = context.getBean("accountDao", AccountDao.class);
        System.out.println("accountDao1 ::: "+accountDao1);
        AccountService accountService2 = context.getBean("accountService", AccountService.class);
        System.out.println("accountService2 ::: "+accountService2);
        AccountDao accountDao2 = context.getBean("accountDao", AccountDao.class);
        System.out.println("accountDao2 ::: "+accountDao2);
    }

    /**
     * 测试声明周期
     */
    @Test
    public void testLif(){
        System.out.println("容器即将创建!");
        ClassPathXmlApplicationContext cpxac =
                new ClassPathXmlApplicationContext("ApplicationContext.xml");
        System.out.println("容器即将关闭!");
        //关闭容器时对象会销毁
        cpxac.close();
    }
}

3.测试

①执行saveAccount()控制台输出

调用了AccountDaoImpl的空参构造创建对象!
AccountDaoImpl对象创建成功!
调用了AccountDaoImpl的空参构造创建对象!
AccountDaoImpl对象创建成功!
调用了AccountServiceImpl的空参构造创建对象!
AccountServiceImpl对象创建成功!
Account{id='2', accountName='Lily', money=1000.0}
账户信息保存成功!

②执行testScope()控制台输出(这里只截取有效信息)

accountService1 ::: com.howie.service.impl.AccountServiceImpl@436e852b
accountService2 ::: com.howie.service.impl.AccountServiceImpl@29b5cd00
accountDao1 ::: com.howie.dao.impl.AccountDaoImpl@32d2fa64
accountDao2 ::: com.howie.dao.impl.AccountDaoImpl@32d2fa64

③执行testLife()控制台输出

容器即将创建!
调用了AccountDaoImpl的空参构造创建对象!
AccountDaoImpl对象创建成功!
容器即将关闭!
AccountDaoImpl对象即将被销毁!

二.总结:

1.对象的创建时机?

spring在程序启动的时候就会将所有的对象全部创建出来置入容器内

需要使用对象的时候,只需要从容器内取出即可

2.单例/多例

bean标签中的scope属性:

singleton	单例模式(默认)
prototype	多例模式

通过上面的测试结果可以看得出二者的区别,这里不再赘述!

3.SpringIOC采用立即加载创建对象

Spring之IOC之sping-context实现立即加载

一.案例展示

二.总结:

內網映射工具之EchoSite

Thread類之join方法

Spring之IOC&DI的差異

Mybatis的XxxMapper.xml中能否配置重載方法

Mybatis的XxxMapper.xml中模糊查詢條件如何拼接

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