2、Spring使用+ioc容器配置使用1

Hello-zhou發表於2020-12-14
Spring

通過前面的介紹我們已經知道了Spring中非常重要的一個特性就是IOC,下面我們將要來看一下如何使用IOC容器，幫助大家更好的體會spring的優勢。

1、spring_helloworld

(1)使用手動載入jar包的方式實現，分為三個步驟，現在幾乎不用

  • 導包：匯入這五個包即可

    commons-logging-1.2.jar spring-beans-5.2.3.RELEASE.jar spring-context-5.2.3.RELEASE.jar spring-core-5.2.3.RELEASE.jar spring-expression-5.2.3.RELEASE.jar

  • 寫配置

    Person.java

    package com.mashibing.bean;

public class Person {
    private int id;
    private String name;
    private int age;
    private String gender;

    public int getId() {
        return id;
    }

    public void setId(int 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 String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "Person{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", gender='" + gender + '\'' +
                '}';
    }
}

    ioc.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">

    <!--註冊一個物件，spring回自動建立這個物件-->
    <!--
    一個bean標籤就表示一個物件
    id:這個物件的唯一標識
    class:註冊物件的完全限定名
    -->
    <bean id="person" class="com.mashibing.bean.Person">
        <!--使用property標籤給物件的屬性賦值
        name:表示屬性的名稱
        value：表示屬性的值
        -->
        <property name="id" value="1"></property>
        <property name="name" value="zhangsan"></property>
        <property name="age" value="18"></property>
        <property name="gender" value="男"></property>
    </bean>
</beans>

  • 測試

SpringDemoTest.java

package com.mashibing.test;

import com.mashibing.bean.Person;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringDemoTest {
    public static void main(String[] args) {
        //ApplicationContext:表示ioc容器
        //ClassPathXmlApplicationContext:表示從當前classpath路徑中獲取xml檔案的配置
        //根據spring的配置檔案來獲取ioc容器物件
        ApplicationContext context = new ClassPathXmlApplicationContext("ioc.xml");
        Person person = (Person) context.getBean("person");
        System.out.println(person);
    }
}

(2)使用maven的方式來構建專案

  • 建立maven專案

    定義專案的groupId、artifactId

  • 新增對應的pom依賴

    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.mashibing</groupId>
    <artifactId>spring_demo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.2.3.RELEASE</version>
        </dependency>
    </dependencies>
</project>

  • 編寫程式碼

    Person.java

    package com.mashibing.bean;
public class Person {
    private int id;
    private String name;
    private int age;
    private String gender;

    public int getId() {
        return id;
    }

    public void setId(int 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 String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    @Override
    public String toString() {
        return "Person{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", gender='" + gender + '\'' +
                '}';
    }
}

  • 測試

    MyTest.java

import com.mashibing.bean.Person;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("ioc.xml");
        Person person = (Person) context.getBean("person");
        System.out.println(person);
    }
}

總結：

​ 以上兩種方式建立spring的專案都是可以的，但是在現在的企業開發環境中使用更多的還是maven這樣的方式，無須自己處理jar之間的依賴關係，也無須提前下載jar包，只需要配置相關的pom即可，因此推薦大家使用maven的方式，具體的maven操作大家可以看maven的詳細操作文件。

​ 搭建spring專案需要注意的點：

​ 1、一定要將配置檔案新增到類路徑中，使用idea建立專案的時候要放在resource目錄下

​ 2、導包的時候別忘了commons-logging-1.2.jar包

​ 細節點：

​ 1、ApplicationContext就是IOC容器的介面，可以通過此物件獲取容器中建立的物件

​ 2、物件在Spring容器建立完成的時候就已經建立完成，不是需要用的時候才建立

​ 3、物件在IOC容器中儲存的時候都是單例的，如果需要多例需要修改屬性

​ 4、建立物件給屬性賦值的時候是通過setter方法實現的

​ 5、物件的屬性是由setter/getter方法決定的，而不是定義的成員屬性

2、spring物件的獲取及屬性賦值方式

1、通過bean的id獲取IOC容器中的物件（上面已經用過）

2、通過bean的型別獲取物件

​ MyTest.java

import com.mashibing.bean.Person;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("ioc.xml");
        Person bean = context.getBean(Person.class);
        System.out.println(bean);
    }
}

注意：通過bean的型別在查詢物件的時候，在配置檔案中不能存在兩個型別一致的bean物件，如果有的話，可以通過如下方法

MyTest.java

import com.mashibing.bean.Person;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("ioc.xml");
        Person person = context.getBean("person", Person.class);
        System.out.println(person);
    }
}

3、通過構造器給bean物件賦值

ioc.xml

	<!--給person類新增構造方法-->
	<bean id="person2" class="com.mashibing.bean.Person">
        <constructor-arg name="id" value="1"></constructor-arg>
        <constructor-arg name="name" value="lisi"></constructor-arg>
        <constructor-arg name="age" value="20"></constructor-arg>
        <constructor-arg name="gender" value="女"></constructor-arg>
    </bean>

	<!--在使用構造器賦值的時候可以省略name屬性，但是此時就要求必須嚴格按照構造器引數的順序來填寫了-->
	<bean id="person3" class="com.mashibing.bean.Person">
        <constructor-arg value="1"></constructor-arg>
        <constructor-arg value="lisi"></constructor-arg>
        <constructor-arg value="20"></constructor-arg>
        <constructor-arg value="女"></constructor-arg>
    </bean>

	<!--如果想不按照順序來新增引數值，那麼可以搭配index屬性來使用-->
    <bean id="person4" class="com.mashibing.bean.Person">
        <constructor-arg value="lisi" index="1"></constructor-arg>
        <constructor-arg value="1" index="0"></constructor-arg>
        <constructor-arg value="女" index="3"></constructor-arg>
        <constructor-arg value="20" index="2"></constructor-arg>
    </bean>
	<!--當有多個引數個數相同，不同型別的構造器的時候，可以通過type來強制型別-->
	將person的age型別設定為Integer型別
	public Person(int id, String name, Integer age) {
        this.id = id;
        this.name = name;
        this.age = age;
        System.out.println("Age");
    }

    public Person(int id, String name, String gender) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        System.out.println("gender");
    }
	<bean id="person5" class="com.mashibing.bean.Person">
        <constructor-arg value="1"></constructor-arg>
        <constructor-arg value="lisi"></constructor-arg>
        <constructor-arg value="20" type="java.lang.Integer"></constructor-arg>
    </bean>
	<!--如果不修改為integer型別，那麼需要type跟index組合使用-->
	 <bean id="person5" class="com.mashibing.bean.Person">
        <constructor-arg value="1"></constructor-arg>
        <constructor-arg value="lisi"></constructor-arg>
        <constructor-arg value="20" type="int" index="2"></constructor-arg>
    </bean>

4、通過名稱空間為bean賦值，簡化配置檔案中屬性宣告的寫法

​ 1、匯入名稱空間

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

​ 2、新增配置

    <bean id="person6" class="com.mashibing.bean.Person" p:id="3" p:name="wangwu" p:age="22" p:gender="男"></bean>

5、為複雜型別進行賦值操作

​ 在之前的測試程式碼中，我們都是給最基本的屬性進行賦值操作，在正常的企業級開發中還會遇到給各種複雜型別賦值，如集合、陣列、其他物件等。

​ Person.java

package com.mashibing.bean;

import java.util.*;

public class Person {
    private int id;
    private String name="dahuang";
    private int age;
    private String gender;
    private Address address;
    private String[] hobbies;
    private List<Book> books;
    private Set<Integer> sets;
    private Map<String,Object> maps;
    private Properties properties;

    public Person(int id, String name, int age, String gender) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.gender = gender;
        System.out.println("有參構造器");
    }

    public Person(int id, String name, int age) {
        this.id = id;
        this.name = name;
        this.age = age;
        System.out.println("Age");
    }

    public Person(int id, String name, String gender) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        System.out.println("gender");
    }

    public Person() {
    }

    public int getId() {
        return id;
    }

    public void setId(int 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 String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    public List<Book> getBooks() {
        return books;
    }

    public void setBooks(List<Book> books) {
        this.books = books;
    }

    public Map<String, Object> getMaps() {
        return maps;
    }

    public void setMaps(Map<String, Object> maps) {
        this.maps = maps;
    }

    public Properties getProperties() {
        return properties;
    }

    public void setProperties(Properties properties) {
        this.properties = properties;
    }

    public String[] getHobbies() {
        return hobbies;
    }

    public void setHobbies(String[] hobbies) {
        this.hobbies = hobbies;
    }

    public Set<Integer> getSets() {
        return sets;
    }

    public void setSets(Set<Integer> sets) {
        this.sets = sets;
    }

    @Override
    public String toString() {
        return "Person{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", gender='" + gender + '\'' +
                ", address=" + address +
                ", hobbies=" + Arrays.toString(hobbies) +
                ", books=" + books +
                ", sets=" + sets +
                ", maps=" + maps +
                ", properties=" + properties +
                '}';
    }
}

Book.java

package com.mashibing.bean;

public class Book {
    private String name;
    private String author;
    private double price;

    public Book() {
    }

    public Book(String name, String author, double price) {
        this.name = name;
        this.author = author;
        this.price = price;
    }

    public String getName() {
        return name;
    }

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

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    @Override
    public String toString() {
        return "Book{" +
                "name='" + name + '\'' +
                ", author='" + author + '\'' +
                ", price=" + price +
                '}';
    }
}

Address.java

package com.mashibing.bean;

public class Address {
    private String province;
    private String city;
    private String town;

    public Address() {
    }

    public Address(String province, String city, String town) {
        this.province = province;
        this.city = city;
        this.town = town;
    }

    public String getProvince() {
        return province;
    }

    public void setProvince(String province) {
        this.province = province;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getTown() {
        return town;
    }

    public void setTown(String town) {
        this.town = town;
    }

    @Override
    public String toString() {
        return "Address{" +
                "province='" + province + '\'' +
                ", city='" + city + '\'' +
                ", town='" + town + '\'' +
                '}';
    }
}

ioc.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"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/util https://www.springframework.org/schema/util/spring-util.xsd"
>

    <!--給複雜型別的賦值都在property標籤內進行-->
    <bean id="person" class="com.mashibing.bean.Person">
        <property name="name">
            <!--賦空值-->
            <null></null>
        </property>
        <!--通過ref引用其他物件，引用外部bean-->
        <property name="address" ref="address"></property>
        <!--引用內部bean-->
       <!-- <property name="address">
            <bean class="com.mashibing.bean.Address">
                <property name="province" value="北京"></property>
                <property name="city" value="北京"></property>
                <property name="town" value="西城區"></property>
            </bean>
        </property>-->
        <!--為list賦值-->
        <property name="books">
            <list>
                <!--內部bean-->
                <bean id="book1" class="com.mashibing.bean.Book">
                    <property name="name" value="多執行緒與高併發"></property>
                    <property name="author" value="馬士兵"></property>
                    <property name="price" value="1000"></property>
                </bean>
                <!--外部bean-->
                <ref bean="book2"></ref>
            </list>
        </property>
        <!--給map賦值-->
        <property name="maps" ref="myMap"></property>
        <!--給property賦值-->
        <property name="properties">
            <props>
                <prop key="aaa">aaa</prop>
                <prop key="bbb">222</prop>
            </props>
        </property>
        <!--給陣列賦值-->
        <property name="hobbies">
            <array>
                <value>book</value>
                <value>movie</value>
                <value>game</value>
            </array>
        </property>
        <!--給set賦值-->
        <property name="sets">
            <set>
                <value>111</value>
                <value>222</value>
                <value>222</value>
            </set>
        </property>
    </bean>
    <bean id="address" class="com.mashibing.bean.Address">
        <property name="province" value="河北"></property>
        <property name="city" value="邯鄲"></property>
        <property name="town" value="武安"></property>
    </bean>
    <bean id="book2" class="com.mashibing.bean.Book">
        <property name="name" value="JVM"></property>
        <property name="author" value="馬士兵"></property>
        <property name="price" value="1200"></property>
    </bean>
    <!--級聯屬性-->
    <bean id="person2" class="com.mashibing.bean.Person">
        <property name="address" ref="address"></property>
        <property name="address.province" value="北京"></property>
    </bean>
    <!--util名稱空間建立集合型別的bean-->
    <util:map id="myMap">
            <entry key="key1" value="value1"></entry>
            <entry key="key2" value-ref="book2"></entry>
            <entry key="key03">
                <bean class="com.mashibing.bean.Book">
                    <property name="name" value="西遊記" ></property>
                    <property name="author" value="吳承恩" ></property>
                    <property name="price" value="100" ></property>
                </bean>
            </entry>
    </util:map>
</beans>

6、繼承關係bean的配置

ioc.xml

    <bean id="person" class="com.mashibing.bean.Person">
        <property name="id" value="1"></property>
        <property name="name" value="zhangsan"></property>
        <property name="age" value="21"></property>
        <property name="gender" value="男"></property>
    </bean>
    <!--parent:指定bean的配置資訊繼承於哪個bean-->
    <bean id="person2" class="com.mashibing.bean.Person" parent="person">
        <property name="name" value="lisi"></property>
    </bean>

如果想實現Java檔案的抽象類，不需要將當前bean例項化的話，可以使用abstract屬性

 	<bean id="person" class="com.mashibing.bean.Person" abstract="true">
        <property name="id" value="1"></property>
        <property name="name" value="zhangsan"></property>
        <property name="age" value="21"></property>
        <property name="gender" value="男"></property>
    </bean>
    <!--parent:指定bean的配置資訊繼承於哪個bean-->
    <bean id="person2" class="com.mashibing.bean.Person" parent="person">
        <property name="name" value="lisi"></property>
    </bean>

7、bean物件建立的依賴關係

​ bean物件在建立的時候是按照bean在配置檔案的順序決定的，也可以使用depend-on標籤來決定順序

ioc.xml

	<bean id="book" class="com.mashibing.bean.Book" depends-on="person,address"></bean>
    <bean id="address" class="com.mashibing.bean.Address"></bean>
    <bean id="person" class="com.mashibing.bean.Person"></bean>

8、bean的作用域控制，是否是單例

ioc.xml

    <!--
    bean的作用域：singleton、prototype、request、session
    預設情況下是單例的
    prototype：多例項的
        容器啟動的時候不會建立多例項bean，只有在獲取物件的時候才會建立該物件
        每次建立都是一個新的物件
    singleton：預設的單例物件
        在容器啟動完成之前就已經建立好物件
        獲取的所有物件都是同一個
    -->
    <bean id="person4" class="com.mashibing.bean.Person" scope="prototype"></bean>

9、利用工廠模式建立bean物件

​ 在之前的案例中，所有bean物件的建立都是通過反射得到對應的bean例項，其實在spring中還包含另外一種建立bean例項的方式，就是通過工廠模式進行物件的建立

​ 在利用工廠模式建立bean例項的時候有兩種方式，分別是靜態工廠和例項工廠。

​ 靜態工廠：工廠本身不需要建立物件，但是可以通過靜態方法呼叫，物件=工廠類.靜態工廠方法名（）；

​ 例項工廠：工廠本身需要建立物件，工廠類 工廠物件=new 工廠類；工廠物件.get物件名（）；

PersonStaticFactory.java

package com.mashibing.factory;

import com.mashibing.bean.Person;

public class PersonStaticFactory {

    public static Person getPerson(String name){
        Person person = new Person();
        person.setId(1);
        person.setName(name);
        return person;
    }
}

ioc.xml

<!--
靜態工廠的使用：
class:指定靜態工廠類
factory-method:指定哪個方法是工廠方法
-->
<bean id="person5" class="com.mashibing.factory.PersonStaticFactory" factory-method="getPerson">
        <!--constructor-arg：可以為方法指定引數-->
        <constructor-arg value="lisi"></constructor-arg>
    </bean>

PersonInstanceFactory.java

package com.mashibing.factory;

import com.mashibing.bean.Person;

public class PersonInstanceFactory {
    public Person getPerson(String name){
        Person person = new Person();
        person.setId(1);
        person.setName(name);
        return person;
    }
}

ioc.xml

    <!--例項工廠使用-->
    <!--建立例項工廠類-->
    <bean id="personInstanceFactory" class="com.mashibing.factory.PersonInstanceFactory"></bean>
    <!--
    factory-bean:指定使用哪個工廠例項
    factory-method:指定使用哪個工廠例項的方法
    -->
    <bean id="person6" class="com.mashibing.bean.Person" factory-bean="personInstanceFactory" factory-method="getPerson">
        <constructor-arg value="wangwu"></constructor-arg>
    </bean>

10、繼承FactoryBean來建立物件

​ FactoryBean是Spring規定的一個介面，當前介面的實現類，Spring都會將其作為一個工廠，但是在ioc容器啟動的時候不會建立例項，只有在使用的時候才會建立物件

MyFactoryBean.java

package com.mashibing.factory;

import com.mashibing.bean.Person;
import org.springframework.beans.factory.FactoryBean;

/**
 * 實現了FactoryBean介面的類是Spring中可以識別的工廠類，spring會自動呼叫工廠方法建立例項
 */
public class MyFactoryBean implements FactoryBean<Person> {

    /**
     * 工廠方法，返回需要建立的物件
     * @return
     * @throws Exception
     */
    @Override
    public Person getObject() throws Exception {
        Person person = new Person();
        person.setName("maliu");
        return person;
    }

    /**
     * 返回建立物件的型別,spring會自動呼叫該方法返回物件的型別
     * @return
     */
    @Override
    public Class<?> getObjectType() {
        return Person.class;
    }

    /**
     * 建立的物件是否是單例物件
     * @return
     */
    @Override
    public boolean isSingleton() {
        return false;
    }
}

ioc.xml

<bean id="myfactorybean" class="com.mashibing.factory.MyFactoryBean"></bean>

11、bean物件的初始化和銷燬方法

​ 在建立物件的時候，我們可以根據需要呼叫初始化和銷燬的方法

Address.java

package com.mashibing.bean;

public class Address {
    private String province;
    private String city;
    private String town;

    public Address() {
        System.out.println("address被建立了");
    }

    public Address(String province, String city, String town) {
        this.province = province;
        this.city = city;
        this.town = town;
    }

    public String getProvince() {
        return province;
    }

    public void setProvince(String province) {
        this.province = province;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public String getTown() {
        return town;
    }

    public void setTown(String town) {
        this.town = town;
    }

    public void init(){
        System.out.println("物件被初始化");
    }
    
    public void destory(){
        System.out.println("物件被銷燬");
    }
    
    @Override
    public String toString() {
        return "Address{" +
                "province='" + province + '\'' +
                ", city='" + city + '\'' +
                ", town='" + town + '\'' +
                '}';
    }
}

ioc.xml

<!--bean生命週期表示bean的建立到銷燬
        如果bean是單例，容器在啟動的時候會建立好，關閉的時候會銷燬建立的bean
        如果bean是多禮，獲取的時候建立物件，銷燬的時候不會有任何的呼叫
    -->
    <bean id="address" class="com.mashibing.bean.Address" init-method="init" destroy-method="destory"></bean>

MyTest.java

import com.mashibing.bean.Address;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("ioc2.xml");
        Address address = context.getBean("address", Address.class);
        System.out.println(address);
        //applicationContext沒有close方法，需要使用具體的子類
        ((ClassPathXmlApplicationContext)context).close();

    }
}

12、配置bean物件初始化方法的前後處理方法

​ spring中包含一個BeanPostProcessor的介面，可以在bean的初始化方法的前後呼叫該方法，如果配置了初始化方法的前置和後置處理器，無論是否包含初始化方法，都會進行呼叫

MyBeanPostProcessor.java

package com.mashibing.bean;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;

public class MyBeanPostProcessor implements BeanPostProcessor {
    /**
     * 在初始化方法呼叫之前執行
     * @param bean  初始化的bean物件
     * @param beanName  xml配置檔案中的bean的id屬性
     * @return
     * @throws BeansException
     */
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("postProcessBeforeInitialization:"+beanName+"呼叫初始化前置方法");
        return bean;
    }

    /**
     * 在初始化方法呼叫之後執行
     * @param bean
     * @param beanName
     * @return
     * @throws BeansException
     */
    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("postProcessAfterInitialization:"+beanName+"呼叫初始化字尾方法");
        return bean;
    }
}

ioc.xml

<bean id="myBeanPostProcessor" class="com.mashibing.bean.MyBeanPostProcessor"></bean>

3、spring建立第三方bean物件

​ 在Spring中，很多物件都是單例項的，在日常的開發中，我們經常需要使用某些外部的單例項物件，例如資料庫連線池，下面我們來講解下如何在spring中建立第三方bean例項。

​ 1、匯入資料庫連線池的pom檔案

<!-- https://mvnrepository.com/artifact/com.alibaba/druid -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.1.21</version>
</dependency>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.47</version>
</dependency>

​ 2、編寫配置檔案

ioc.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">

    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="username" value="root"></property>
        <property name="password" value="123456"></property>
        <property name="url" value="jdbc:mysql://localhost:3306/demo"></property>
        <property name="driverClassName" value="com.mysql.jdbc.Driver"></property>
    </bean>
</beans>

​ 3、編寫測試檔案

MyTest.java

import com.alibaba.druid.pool.DruidDataSource;
import com.mashibing.bean.Address;
import com.mashibing.bean.Person;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import java.sql.SQLException;

public class MyTest {
    public static void main(String[] args) throws SQLException {
        ApplicationContext context = new ClassPathXmlApplicationContext("ioc3.xml");
        DruidDataSource dataSource = context.getBean("dataSource", DruidDataSource.class);
        System.out.println(dataSource);
        System.out.println(dataSource.getConnection());
    }
}

4、spring引用外部配置檔案

在resource中新增dbconfig.properties

username=root
password=123456
url=jdbc:mysql://localhost:3306/demo
driverClassName=com.mysql.jdbc.Driver

編寫配置檔案

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">
	<!--載入外部配置檔案
		在載入外部依賴檔案的時候需要context名稱空間
	-->
    <context:property-placeholder location="classpath:dbconfig.properties"/>
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="username" value="${username}"></property>
        <property name="password" value="${password}"></property>
        <property name="url" value="${url}"></property>
        <property name="driverClassName" value="${driverClassName}"></property>
    </bean>
</beans>

5、spring基於xml檔案的自動裝配

​ 當一個物件中需要引用另外一個物件的時候，在之前的配置中我們都是通過property標籤來進行手動配置的，其實在spring中還提供了一個非常強大的功能就是自動裝配，可以按照我們指定的規則進行配置，配置的方式有以下幾種：

autowire:

​ default/no：不自動裝配

​ byName：按照名字進行裝配，以屬性名作為id去容器中查詢元件，進行賦值，如果找不到則裝配null

​ byType：按照型別進行裝配,以屬性的型別作為查詢依據去容器中找到這個元件，如果有多個型別相同的bean物件，那麼會報異常，如果找不到則裝配null

​ constructor：按照構造器進行裝配，先按照有參構造器引數的型別進行裝配，沒有就直接裝配null；如果按照型別找到了多個，那麼就使用引數名作為id繼續匹配，找到就裝配，找不到就裝配null

ioc.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">

    <bean id="address" class="com.mashibing.bean.Address">
        <property name="province" value="河北"></property>
        <property name="city" value="邯鄲"></property>
        <property name="town" value="武安"></property>
    </bean>
    <bean id="person" class="com.mashibing.bean.Person" autowire="byName"></bean>
    <bean id="person2" class="com.mashibing.bean.Person" autowire="byType"></bean>
    <bean id="person3" class="com.mashibing.bean.Person" autowire="constructor"></bean>
</beans>

6、SpEL的使用

​ SpEL:Spring Expression Language,spring的表示式語言，支援執行時查詢操作物件

​ 使用#{...}作為語法規則，所有的大括號中的字元都認為是SpEL.

ioc.xml

    <bean id="person4" class="com.mashibing.bean.Person">
        <!--支援任何運算子-->
        <property name="age" value="#{12*2}"></property>
        <!--可以引用其他bean的某個屬性值-->
        <property name="name" value="#{address.province}"></property>
        <!--引用其他bean-->
        <property name="address" value="#{address}"></property>
        <!--呼叫靜態方法-->
        <property name="hobbies" value="#{T(java.util.UUID).randomUUID().toString().substring(0,4)}"></property>
        <!--呼叫非靜態方法-->
        <property name="gender" value="#{address.getCity()}"></property>
    </bean>

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