Ioc和Aop扩展--多种方式实现依赖注入(构造注入,p命名空间注入,集合类型注入,注入null和注入空值)

构造注入

语法：

<constructor-arg>

   <ref bean=“bean的id”/>

</constructor-arg>

1.首先创建一个实体类，一定要有带参构造

public class UserEntity {
    private Integer id;
    private String name;
    private String pwd;
    private CardEntity myCard;

    public UserEntity() {
        System.out.println("UserEntity初始化============================");
    }

    public UserEntity(Integer id, String name, String pwd, CardEntity myCard) {
        super();
        this.id = id;
        this.name = name;
        this.pwd = pwd;
        this.myCard = myCard;
    }
    // 省略get,set
}

2.创建dao

public interface UserEntityDao {
    public void save(UserEntity user);
}

2.创建dao实现类

public class UserEntityDaoImpl implements UserEntityDao {

    @Override
    public void save(UserEntity user) {
    }

}

3.创建biz

public interface UserEntityBiz {
    public void save(UserEntity user);

}

4.创建biz实现类,植入一个dao对象

public class UserEntityBizImpl implements UserEntityBiz {
    private UserEntityDao userDao;

    public UserEntityBizImpl() {
    }

    public void UserEntityBizImpl(UserEntityDao userDao) {
        this.userDao = userDao;
    }
    
    @Override
    public void save(UserEntity user) {
        userDao.save(user);
        System.out.println("===保存成功====");
    }
    //省略get,set
}

5.配置xml

<bean id="card" class="cn.cnsdhzzl.entity.CardEntity">
        <property name="id" value="123"></property>
        <property name="cardNumber" value="1111111110000"></property>
    </bean>

    <bean id="userDao" class="cn.cnsdhzzl.dao.impl.UserEntityDaoImpl" />

    <bean id="userBiz" class="cn.cnsdhzzl.biz.impl.UserEntityBizImpl">
        <constructor-arg>
            <ref bean="userDao"></ref>
        </constructor-arg>
    </bean>

    <bean id="userEntity" class="cn.cnsdhzzl.entity.UserEntity">
        <constructor-arg index="0" type="java.lang.Integer"
            value="001" />
        <constructor-arg index="1" type="java.lang.String"
            value="002用户" />
        <constructor-arg index="2" type="java.lang.String"
            value="003用户密码" />
        <constructor-arg index="3" ref="card" />
    </bean>

6.测试

@Test
    /*
     * 构造注入
     */
    public void constructorSpring() {
        ApplicationContext ac = new ClassPathXmlApplicationContext(
                "applicationContext.xml");
        UserEntityBizImpl biz = (UserEntityBizImpl) ac.getBean("userBiz");
        UserEntity ue = (UserEntity) ac.getBean("userEntity");
        biz.save(ue);
        System.out.println(ue.toString());
}

p命名空间注入

语法：

p:属性名=“属性值”

p:属性名-ref=“bean的id”

1.准备一个实体类

public class CardEntity {
    private Integer id;
    private String cardNumber;

    public CardEntity() {
    }

    public CardEntity(Integer id, String cardNumber) {
        this.id = id;
        this.cardNumber = cardNumber;
    }

    @Override
    public String toString() {
        return "CardEntity [id=" + id + ", cardNumber=" + cardNumber + "]";
    }
    //省略get,set
}

2.配置xml

<!-- 使用p空间实现属性注入 -->
    <bean id="card" class="cn.cnsdhzzl.entity.CardEntity" p:id="001"
        p:cardNumber="62256549361" />

3.测试

@Test
    /*
     * P命名空间注入
     */
    public void PInjection() {
        CardEntity card = (CardEntity) ac.getBean("card");
        System.out.println(card.toString());
    }

注：如果属性中包括了xml中的特殊字符（&、<、>、"、'），则注入时需要进行处理，通常可以采用两种方法：使用<![CDATA[]]>标记或把字符串替换为实体引用。

xml中预定义的实体引用

符号	实体引用	符号	实体引用
<	&lt;	'	&apos;
>	&gt;	"	&quot;
&	&amp;

。

注入集合类型的属性

1.list

<bean id="user" class="cn.cnsdhzzl.entity.UserEntity">
        <property name="hobbies">
            <list>
                <value>计算机</value>
                <value>运动</value>
            </list>
        </property>
    </bean>

2.set

<bean id="user" class="cn.cnsdhzzl.entity.UserEntity">
        <property name="hobbies">
            <set>
                <value>计算机</value>
                <value>运动</value>
            </set>
        </property>
    </bean>

3.map

<bean id="user" class="cn.cnsdhzzl.entity.UserEntity">
        <property name="hobbies">
            <map>
                <entry>
                    <value>计算机</value>
                </entry>
                <entry>
                    <value>运动</value>
                </entry>
            </map>
        </property>
    </bean>

4.props

<bean id="user" class="cn.cnsdhzzl.entity.UserEntity">
        <property name="hobbies">
            <props>
                <prop key="computer">计算机</prop>
                <prop key="motion">运动</prop>
            </props>
        </property>
    </bean>

5.注入null和空值

<!-- 注入空字符串 -->
    <bean id="user" class="cn.cnsdhzzl.entity.UserEntity">
        <property name="hobbies">
            <value></value>
        </property>
    </bean>

<!-- 注入null -->
    <bean id="user" class="cn.cnsdhzzl.entity.UserEntity">
        <property name="hobbies">
            <null></null>
        </property>
    </bean>