Spring之IOC之sping-context實現立即加載

通過之前的學習使用BeanFactory通過延遲加載實現了全部對象的創建並存儲到了容器map中

今天學習SpringIOC的spring-context如何實現立即加載!

預習:

需要引入依賴:spring-context
bean標籤的解釋:
- ①id:從容器中準確取出對象的唯一標識,接口類文件名(開頭字母小寫)
- ②class:所要創建對象的實現類全路徑
- ③scope:代表創建對象的範圍:
  - 1>singleton:default 單例模式:即全局使用的都是同一個對象後期對象由Spring維護(生存&銷燬)
    - 創建出來的對象地址全部一致
  - 2>prototype:多例模式:需要時就創建一個新的對象,不保證唯一後期對象不由Spring維護
    - 創建出來的對象的地址有可能不一致
生命週期:
- init-method:對象創建之後執行的方法
- destroy-method:對象銷燬之前執行的方法

一.案例展示

1.測試準備

項目準備:

2.代碼展示:

***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>
        <!--單元測試-->
        <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">
    <!--配置對象創建信息-->
    <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 {
    /**
     * 保存賬戶信息
     * @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 {

    /**
     * 爲了觀察生命週期,在空參構造中加入提示信息
     */
    public AccountDaoImpl() {
        System.out.println("調用了AccountDaoImpl的空參構造創建對象!");
    }

    public void initShow(){
        System.out.println("AccountDaoImpl對象創建成功!");
    }
    public void destoryShow(){
        System.out.println("AccountDaoImpl對象即將被銷燬!");
    }
    /**
     * 保存賬戶信息
     * 模擬保存數據至數據庫的操作
     * @param account
     */
    public void saveAccount(Account account) {
        System.out.println(account);
        System.out.println("賬戶信息保存成功!");
    }
}

***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 {

    /**
     * 保存賬戶信息
     * @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;
    /**
     * 爲了觀察生命週期,在空參構造中加入提示信息
     */
    public AccountServiceImpl() {
        //獲取spring容器對象
        ClassPathXmlApplicationContext context =
                new ClassPathXmlApplicationContext("ApplicationContext.xml");
        this.accountDao = context.getBean("accountDao",AccountDao.class);
        System.out.println("調用了AccountServiceImpl的空參構造創建對象!");
    }

    public void initShow(){
        System.out.println("AccountServiceImpl對象創建成功!");
    }
    public void destoryShow(){
        System.out.println("AccountServiceImpl對象即將被銷燬!");
    }
    /**
     * 保存用戶信息
     * @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 {

    /**
     * 保存賬戶
     */
    @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);
    }


    /**
     * 測試多例模式
     */
    @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);
    }

    /**
     * 測試聲明週期
     */
    @Test
    public void testLif(){
        System.out.println("容器即將創建!");
        ClassPathXmlApplicationContext cpxac =
                new ClassPathXmlApplicationContext("ApplicationContext.xml");
        System.out.println("容器即將關閉!");
        //關閉容器時對象會銷燬
        cpxac.close();
    }
}

3.測試

①執行saveAccount()控制檯輸出

調用了AccountDaoImpl的空參構造創建對象!
AccountDaoImpl對象創建成功!
調用了AccountDaoImpl的空參構造創建對象!
AccountDaoImpl對象創建成功!
調用了AccountServiceImpl的空參構造創建對象!
AccountServiceImpl對象創建成功!
Account{id='2', accountName='Lily', money=1000.0}
賬戶信息保存成功!

②執行testScope()控制檯輸出(這裏只截取有效信息)

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執行testLife()控制檯輸出

容器即將創建!
調用了AccountDaoImpl的空參構造創建對象!
AccountDaoImpl對象創建成功!
容器即將關閉!
AccountDaoImpl對象即將被銷燬!

二.總結:

1.對象的創建時機?

spring在程序啓動的時候就會將所有的對象全部創建出來置入容器內

需要使用對象的時候,只需要從容器內取出即可

2.單例/多例

bean標籤中的scope屬性:

singleton	單例模式(默認)
prototype	多例模式

通過上面的測試結果可以看得出二者的區別,這裏不再贅述!

3.SpringIOC採用立即加載創建對象

Spring之IOC之sping-context實現立即加載

一.案例展示

二.總結:

HTTP URL 詳解

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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