Question

我正在尝试使用util名称空间注入HashMap对象，但无法获取该对象的HashMap类（正在打印LinkedHashMap类名称。）无法弄清楚为什么会这样。

在此测试中，我在Spring jar下方使用：

1. spring-beans-5.0.7.RELEASE.jar 
2. spring-context-5.0.7.RELEASE.jar 
3. spring-core-5.0.7.RELEASE.jar 
4. spring-expression-5.0.7.RELEASE.jar 
5. commons-logging-1.1.1.jar

Bean类：

        package com.vitp.pkg1;

        import java.util.HashMap;

        public class ActualCollections {

            private HashMap<String,Integer> student;

            public void setStudent(HashMap<String, Integer> student) {
                this.student = student;
            }

            public void displayData()
            {
                 System.out.println("Map data(Student<name,rollnumber>) : ---default is LinkedHashMap And actual is :: "+student.getClass().getName());
                 for(String key : student.keySet())
                 {
                     System.out.println(key+"::"+student.get(key));
                 }
            }
        }

用于测试输出的驱动程序类：

        package com.vitp.start;

        import org.springframework.context.ApplicationContext;
        import org.springframework.context.support.ClassPathXmlApplicationContext;

        import com.vitp.pkg1.ActualCollections;
        import com.vitp.pkg1.DefaultCollections;

        public class ActualCollectionObjectInjectionTest {

            public static void main(String... s)
            {
                ApplicationContext beans = new ClassPathXmlApplicationContext("/com/vitp/resources/particular_collection.xml");
                ActualCollections pc = (ActualCollections) beans.getBean("pc");
                pc.displayData();
            }
        }

xml配置文件：

        <!--In this case we need to make use of util namespace so will use xsd instate of dtd.-->

        <beans xmlns="http://www.springframework.org/schema/beans"
               xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
               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 http://www.springframework.org/schema/util/spring-util.xsd">

            <bean id="pc" class="com.vitp.pkg1.ActualCollections">
                <!--Set Map attribute with setter injection-->
                <property name="student">
                    <util:map map-class="java.util.HashMap">
                        <!-- demonstrating various ways on values for entry-->
                        <entry key="Sachin" value="1"/>
                        <!--way2-->               
                        <entry key="Rahul">
                            <value>2</value>
                        </entry>
                        <!--way3-->
                        <entry key="Vinayak" value-ref="three"/>
                        <!--way4-->
                        <entry key="Salman">
                            <ref bean="four"/>
                        </entry>
                    </util:map>
                </property>
            </bean>

            <bean id="three" class="java.lang.Integer">
                <constructor-arg index="0">
                    <value>3</value>
                </constructor-arg>
            </bean>

            <bean id="four" class="java.lang.Integer">
                <constructor-arg index="0">
                    <value>4</value>
                </constructor-arg>
            </bean>

        </beans>

结果是：

            Sep 09, 2018 7:17:03 PM org.springframework.context.support.AbstractApplicationContext prepareRefresh
            INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@27f8302d: startup date [Sun Sep 09 19:17:03 IST 2018]; root of context hierarchy
            Sep 09, 2018 7:17:03 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
            INFO: Loading XML bean definitions from class path resource [com/vitp/resources/particular_collection.xml]
            Map data(Student<name,rollnumber>) : ---default is LinkedHashMap And actual is :: java.util.LinkedHashMap
            Rahul::2
            Vinayak::3
            Sachin::1
            Salman::4

我希望它应该是HashMap类。

Answer 1

您缺少Map的id属性。如果您将id用作地图，则可以使用。工作代码：

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       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 http://www.springframework.org/schema/util/spring-util.xsd">

    <bean id="pc" class="com.vitp.pkg1.ActualCollections">
        <property name="student" ref="someId"/>
    </bean>

    <util:map id="someId" map-class="java.util.HashMap">
        <!-- demonstrating various ways on values for entry-->
        <entry key="Sachin" value="1"/>
        <!--way2-->               
        <entry key="Rahul">
            <value>2</value>
        </entry>
        <!--way3-->
        <entry key="Vinayak" value-ref="three"/>
        <!--way4-->
        <entry key="Salman">
            <ref bean="four"/>
        </entry>
    </util:map>

    <bean id="three" class="java.lang.Integer">
        <constructor-arg index="0">
            <value>3</value>
        </constructor-arg>
    </bean>

    <bean id="four" class="java.lang.Integer">
        <constructor-arg index="0">
            <value>4</value>
        </constructor-arg>
    </bean>

</beans>

在春季

1 个答案: