Spring框架之XML配置文件的使用

拼搏现实的明天。 2022-09-10 00:26 195阅读 0赞

> IOC : 控制反转 Inversion of Controller，IOC本质上是一个概念，是一种思想，控制反转就是对对象控制权的转移，SpringIOC容器创建对象，然后将对象的使用权交出去。

### 基于XML配置文件方式的使用 ###

使用`maven`引入Spring相关的依赖

<properties>
        <java.version>1.8</java.version>
        <spring.verson>5.3.9</spring.verson>
        <junit.version>5.7.2</junit.version>
    </properties>
    <dependencies>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-context</artifactId>
                <version>${spring.verson}</version>
            </dependency>
    
            <dependency>
                <groupId>org.junit.jupiter</groupId>
                <artifactId>junit-jupiter-engine</artifactId>
                <version>${junit.version}</version>
                <scope>test</scope>
            </dependency>
            
            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>1.18.20</version>
                <scope>provided</scope>
            </dependency>
        </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.22.2</version>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.8.1</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

创建 UserBean.java

package org.spring.ss.pojo;
    
    import lombok.Data;
    import lombok.NoArgsConstructor;
    
    @Data
    @NoArgsConstructor
    public class UserBean { 
        private String name;
        private Integer age;
        private String[] favorites;
    
        public UserBean(String name, Integer age) { 
            this.name = name;
            this.age = age;
        }
    
        public void say() { 
            System.out.println("say");
        }
    }

在 `resources`中添加`spring`配置文件`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">
    	
    	<bean class="org.spring.ss.pojo.UserBean" id="userBean"/>
    </beans>

测试

/** * IoC的方式获取 UserBean 对象 */
    @Test
    public void sayTestIoc() { 
        // ioc 容器初始化
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        // ioc 通过bean 的 id 获取指定的bean
        UserBean userBean = (UserBean) applicationContext.getBean("userBean");
        // 使用bean
        userBean.say();
    }

### 从容器中获取对象的方式 ###

*  根据ID获取，`IOC`容器中同一个`bean`只有一个`id`
 *  根据`name`获取，`IOC`容器中同一个`bean`可以声明一个或者多个`name`
    
        
        <bean class="org.spring.ss.pojo.UserBean" id="userBean" name="userBean2,u,uu"/>
        <bean class="org.spring.ss.pojo.UserBean" id="userBean3"/>
 *  根据类型，可以根据需要获取的对象的类型从容器中获取对象
    
        @Test
        public void sayTestIoc2() { 
            // ioc 容器初始化 , 调用UserBean中无参构造器创建对象
            ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
            UserBean userBean = applicationContext.getBean(UserBean.class);
            // 使用bean
            userBean.say();
        }
    
    如果同一类型的对象在容器中有多个，这个时候只根据类型来查找，程序就会报错。
    
        <?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="org.spring.ss.pojo.UserBean" id="userBean" name="userBean2,u,uu"/>
            <bean class="org.spring.ss.pojo.UserBean" id="userBean3"/>
        </beans>
    
    ![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA54Wn54mp5Y2O_size_20_color_FFFFFF_t_70_g_se_x_16]  
    这时候，只能通过`getBean`方法中的组合条件查找。
    
        @Test
        public void sayTestIoc3() { 
            // ioc 容器初始化
            ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
            // ioc 根据 类型 获取指定的bean， 通过类型获取的时候，如果同一类型的 bean 有多个，会报错
        // UserBean userBean = applicationContext.getBean(UserBean.class);
            // 可以组合条件查找
            UserBean userBean = applicationContext.getBean("userBean3", UserBean.class);
            // 使用bean
            userBean.say();
        }
    
    另外，还可以在`<bean>` 中设置 `primary`属性为`true`，那么当同一类型有多个对象时，会优先返回`primary`属性所在的对象
    
        <?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="org.spring.ss.pojo.UserBean" id="userBean" name="userBean2,u,uu"/>
            <bean class="org.spring.ss.pojo.UserBean" id="userBean3"/>
            
            <bean class="org.spring.ss.pojo.UserBean" id="userBean4" primary="true"/>
        </beans>

### 工厂注入 ###

##### 静态工厂注入 #####

StaticFactory.java

package org.spring.ss.factory;
    
    import org.spring.ss.pojo.UserBean;
    
    public class StaticFactory { 
    
        /** * 静态工厂提供的方法 * * @return */
        public static UserBean getInstance() { 
            return new UserBean("Jupiter", 18);
        }
    }

在 `applicationContext.xml`中添加配置

<bean id="userBean5" class="org.spring.ss.factory.StaticFactory" factory-method="getInstance"/>

junit test

@Test
        public void sayTestIoc5() { 
            // ioc 容器初始化
            ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
            UserBean userBean = applicationContext.getBean("userBean5", UserBean.class);
            System.out.println(userBean);
        }

输出：

UserBean(name=Jupiter, age=18)

##### 动态工厂注入 #####

DynamicFactory.java

package org.spring.ss.factory;
    
    import org.spring.ss.pojo.UserBean;
    
    public class DynamicFactory { 
        public UserBean getUserBean() { 
            return new UserBean("join", 13);
        }
    
        public UserBean getUserBean2() { 
            return new UserBean("chai", 15);
        }
    }

在 `applicationContext.xml`中添加配置

<bean class="org.spring.ss.factory.DynamicFactory" id="dynamicFactory"/>
    <bean id="userBean6" factory-bean="dynamicFactory" factory-method="getUserBean"/>
    <bean id="userBean7" factory-bean="dynamicFactory" factory-method="getUserBean2"/>

junit test

@Test
    public void sayTestIoc6() { 
        // ioc 容器初始化
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserBean userBean1 = applicationContext.getBean("userBean6", UserBean.class);
        UserBean userBean2 = applicationContext.getBean("userBean7", UserBean.class);
        System.out.println(userBean1);
        System.out.println(userBean2);
    }

输出：

UserBean(name=join, age=13)
    UserBean(name=chai, age=15)

### 属性注入【DI】 ###

属性注入主要是指如何给对象中的属性赋值

##### 构造注入 #####

> 构造注入, 构造注入需要提供对应的有参构造方法

在`applicationContext.xml`中添加配置

<bean id="userBean8" class="org.spring.ss.pojo.UserBean">
        <constructor-arg name="name" value="DIByConstructor"/>
        <constructor-arg name="age" value="10"/>
        
        
    </bean>

添加测试方法

@Test
    public void testDI() { 
        // ioc 容器初始化
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserBean userBean = applicationContext.getBean("userBean8", UserBean.class);
        System.out.println(userBean);
    }

输出：`UserBean(name=DIByConstructor, age=10)`

##### 设置注入 #####

在`applicationContext.xml`中添加配置

<bean id="userBean9" class="org.spring.ss.pojo.UserBean">
        <property name="name" value="DIBySet"/>
        <property name="age" value="20"/>
    </bean>

添加测试方法

@Test
    public void testDI2() { 
        // ioc 容器初始化
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserBean userBean = applicationContext.getBean("userBean9", UserBean.class);
        System.out.println(userBean);
    }

输出：`UserBean(name=DIBySet, age=20)`

##### 简化构造注入和设值注入的操作 #####

引入对应的名称空间

xmlns:p="http://www.springframework.org/schema/p"
    xmlns:c="http://www.springframework.org/schema/c"

![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBA54Wn54mp5Y2O_size_20_color_FFFFFF_t_70_g_se_x_16 1]  
`applicationContext.xml`的配置也可以写成这样：

<bean id="userBean8" class="org.spring.ss.pojo.UserBean" c:_0="DIByConstructor" c:_1="10" />
    
    
    
    
    
    <bean id="userBean9" class="org.spring.ss.pojo.UserBean" p:age="20" p:name="DIBySet"/>

##### 其他类型的注入写法 #####

创建Cat.java

package org.spring.ss.pojo;
    
    import lombok.Data;
    
    @Data
    public class Cat { 
        private String color;
        private String nick;
    }

修改`UserBean.java`为：

package org.spring.ss.pojo;
    
    import lombok.Data;
    import lombok.NoArgsConstructor;
    
    import java.util.List;
    import java.util.Map;
    import java.util.Properties;
    
    @Data
    @NoArgsConstructor
    public class UserBean { 
        private String name;
        private Integer age;
        private String[] favorites;
        private List<Cat> cats;
        private Map<String, Object> map;
        private Properties props;
    
        public UserBean(String name, Integer age) { 
            this.name = name;
            this.age = age;
        }
    
        public void say() { 
            System.out.println("say");
        }
    }

使用`applicationContext.xml`进行设置属性

<bean id="userBean10" class="org.spring.ss.pojo.UserBean">
        <property name="name" value="DIBySet"/>
        <property name="age" value="20"/>
        <property name="favorites">
            <array>
                <value>篮球</value>
                <value>爬山</value>
                <value>逛街</value>
            </array>
        </property>
        <property name="cats">
            <list>
                <bean class="org.spring.ss.pojo.Cat">
                    <property name="color" value="红色"/>
                    <property name="nick" value="肥猫"/>
                </bean>
                <bean class="org.spring.ss.pojo.Cat">
                    <property name="color" value="黄色"/>
                    <property name="nick" value="咖啡毛"/>
                </bean>
            </list>
        </property>
        <property name="map">
            <map>
                <entry key="name1" value="张三1"/>
                <entry key="name2" value="张三2"/>
                <entry key="name3" value="张三3"/>
            </map>
        </property>
        <property name="props">
            <props>
                <prop key="username">root</prop>
                <prop key="password">123</prop>
            </props>
        </property>
    </bean>

添加测试方法

@Test
    public void testDI3() { 
        // ioc 容器初始化
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserBean userBean = applicationContext.getBean("userBean10", UserBean.class);
        System.out.println(userBean);
    }

输出：`UserBean(name=DIBySet, age=20, favorites=[篮球, 爬山, 逛街], cats=[Cat(color=红色, nick=肥猫), Cat(color=黄色, nick=咖啡毛)], map={name1=张三1, name2=张三2, name3=张三3}, props={password=123, username=root})`

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