Question

我已经更新了以下文件。我的问题是：

错误消息是什么意思？
在E.java的MethodE（）中，我能够执行最后两行，

this.b = new B（this.entities）; this.b.MethodA（）;

而不是使用new，使用Spring Annotation？谢谢你们！

main.java

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


public class main {

    public static void main(String[] args) {
         ApplicationContext context = 
                 new ClassPathXmlApplicationContext("spring.xml");

          E obj = (E) context.getBean("e");

          obj.MethodE();;

    }

}

A.java

import java.util.Collection;


public abstract class A<T> {
    private Collection<T> entities;
    public A(Collection<T> entities){
            this.entities = entities;
    }

public void MethodA() {
    //To process entities such as save them to Database by using Hibernate.
    System.out.println("this is MethodA of Class A");
}
}

B.java

import java.util.Collection;
import java.util.Iterator;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Required;
import org.springframework.stereotype.Component;

@SuppressWarnings({ "hiding", "rawtypes" })
@Component
public class B<Class> extends A {
    private C c;
    private D d;
    private Collection<Class> entities;

    @SuppressWarnings("unchecked")
    public B(Collection<Class> entities) {
        super(entities);
        // TODO Auto-generated constructor stub
        this.entities = entities;
        for(Iterator iterator = entities.iterator(); iterator.hasNext();){
            if (iterator.next() instanceof C)
                this.c = (C) iterator.next();
            if(iterator.next() instanceof D)
                this.d = (D) iterator.next();
        }
    }

    public C getC() {
        return c;
    }

    @Autowired
    public void setC(C c) {
        this.c = c;
    }

    public D getD() {
        return d;
    }

    @Autowired
    public void setD(D d) {
        this.d = d;
    }


    @Override
    public void MethodA() {
        System.out.println("this is override methodA to see if injection works." + this.d.getStrAttr1());
    }

}

C.java

import org.springframework.stereotype.Component;

@Component
public class C {
    private String  strAttr1;
    private int     iAttr2;
    public String getStrAttr1() {
        return strAttr1;
    }
    public void setStrAttr1(String strAttr1) {
        this.strAttr1 = strAttr1;
    }
    public int getiAttr2() {
        return iAttr2;
    }
    public void setiAttr2(int iAttr2) {
        this.iAttr2 = iAttr2;
    }


}

D.java

import org.springframework.stereotype.Component;

@Component
public class D {
    private String  strAttr1;
    private int     iAttr2;
    public String getStrAttr1() {
        return strAttr1;
    }
    public void setStrAttr1(String strAttr1) {
        this.strAttr1 = strAttr1;
    }
    public int getiAttr2() {
        return iAttr2;
    }
    public void setiAttr2(int iAttr2) {
        this.iAttr2 = iAttr2;
    }
}

E.java

import java.util.Collection;

import org.springframework.stereotype.Component;

@Component
public class E {
    private C c;
    private D d;
    private B b;

    private Collection<Class> entities;

    public E() {
    }

    @SuppressWarnings("unchecked")
    public void MethodE(){
        this.c.setStrAttr1("this is my class C's attr1");
        this.c.setiAttr2(9);

        this.d.setStrAttr1("this is my class D's attr1");
        this.d.setiAttr2(7);

        this.entities.addAll((Collection<? extends Class>) this.c);
        this.entities.addAll((Collection<? extends Class>) this.d);

        this.b = new B(this.entities);
        this.b.MethodA();

    }
}

spring.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:tx="http://www.springframework.org/schema/tx"
        xmlns:context="http://www.springframework.org/schema/context"
        xsi:schemaLocation="
   http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-4.1.xsd
   http://www.springframework.org/schema/tx
   http://www.springframework.org/schema/tx/spring-tx-4.1.xsd
   http://www.springframework.org/schema/context
   http://www.springframework.org/schema/context/spring-context-4.1.xsd"
   default-autowire="byName">
    <context:annotation-config/>
    <context:component-scan base-package=""/>


</beans>

错误讯息：

Exception in thread "main" org.apache.commons.logging.LogConfigurationException: org.apache.commons.logging.LogConfigurationException: java.lang.NullPointerException (Caused by java.lang.NullPointerException) (Caused by org.apache.commons.logging.LogConfigurationException: java.lang.NullPointerException (Caused by java.lang.NullPointerException))
    at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:543)
    at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:235)
    at org.apache.commons.logging.impl.LogFactoryImpl.getInstance(LogFactoryImpl.java:209)
    at org.apache.commons.logging.LogFactory.getLog(LogFactory.java:351)
    at org.springframework.context.support.AbstractApplicationContext.<init>(AbstractApplicationContext.java:145)
    at org.springframework.context.support.AbstractRefreshableApplicationContext.<init>(AbstractRefreshableApplicationContext.java:84)
    at org.springframework.context.support.AbstractRefreshableConfigApplicationContext.<init>(AbstractRefreshableConfigApplicationContext.java:59)
    at org.springframework.context.support.AbstractXmlApplicationContext.<init>(AbstractXmlApplicationContext.java:58)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:136)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
    at main.main(main.java:9)
Caused by: org.apache.commons.logging.LogConfigurationException: java.lang.NullPointerException (Caused by java.lang.NullPointerException)
    at org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:397)
    at org.apache.commons.logging.impl.LogFactoryImpl.newInstance(LogFactoryImpl.java:529)
    ... 10 more
Caused by: java.lang.NullPointerException
    at org.apache.commons.logging.impl.LogFactoryImpl.getLogConstructor(LogFactoryImpl.java:374)
    ... 11 more

集合<t>作为构造函数参数，如何使用Spring实现这个？</t>

0 个答案: