gpt4 book ai didi

java - 使用 ApplicationContext 初始化 bean 时发生类转换异常

转载 作者:行者123 更新时间:2023-12-02 13:17:30 24 4
gpt4 key购买 nike

我需要您的帮助来解决有关 spring bean 初始化的问题。以下是该问题的详细信息:

dao接口(interface)

  package com.dao;

import com.entity.Employee;

public interface IEmployeeDao {

Employee create(final Employee aEmployee);
Employee fetchEmployeeById(final Integer aEmployeeId);
}

dao impl 类

  package com.dao.impl;

import javax.persistence.EntityManager;

import com.dao.IEmployeeDao;
import com.entity.Employee;

public class EmployeeDao implements IEmployeeDao {

private EntityManager em;

@Override
public Employee create(Employee aEmployee) {
return this.em.merge(aEmployee);
}

@Override
public Employee fetchEmployeeById(Integer aEmployeeId) {
return this.em.find(Employee.class, aEmployeeId);
}
}

主类:

  package com.client;

import java.sql.SQLException;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.dao.impl.EmployeeDao;

public class Client {
private static final Logger LOGGER = LogManager.getLogger(Client.class);

public static void main(String[] args) throws ClassNotFoundException,
SQLException {
ApplicationContext applicationContext = new
ClassPathXmlApplicationContext(new String[] {"applicationcontext.xml"});
LOGGER.info("client invoked");
EmployeeDao employeeDao =
(EmployeeDao)applicationContext.getBean("employeeDao");
//....some code below
}
}

我试图获取employeeDao bean的代码中的最后一行抛出以下异常:

  Exception in thread "main" java.lang.ClassCastException: 
com.sun.proxy.$Proxy17 cannot be cast to
com.dao.impl.EmployeeDao
at com.client.Client.main(Client.java:26)

根据我浏览的一些答案中的建议,我更改了上面的行以转换为接口(interface)而不是其实现类

    IEmployeeDao employeeDao =  
(IEmployeeDao)applicationContext.getBean("employeeDao");

bean 被注入(inject),没有任何异常,但现在实际的实现方法没有被调用,即现在当我调用 EmployeedDao 的 create 方法时,如下所示

  employeeDao.create(new Employee());

创建方法实现未被调用,即以下方法:

  @Override
public Employee create(Employee aEmployee) {
System.out.println("com.dao.impl.EmployeeDao.create(Employee) callled")
return this.em.merge(aEmployee);
}

我通过放置一条 sysout 消息来确认这一点。

请告诉我我做错了什么或者可以采取什么措施来解决这个问题。我还在下面发布了 bean 配置文件和 Maven 依赖项。

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"
xmlns:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd ">
<import resource="aspects.xml"/>
<bean id="employeeDao" class="com.dao.impl.EmployeeDao" />

</beans>

方面.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:aop="http://www.springframework.org/schema/aop"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-2.5.xsd ">

<bean id="logAspect"
class="com.logging.LoggingAspect" />

<aop:config>

<aop:aspect id="aspectLoggging" ref="logAspect">
<aop:pointcut id="pointCutAround"
expression="execution(*
com.dao.IEmployeeDao.*(..))" />

aop:around method="logAround" pointcut-ref="pointCutAround" />

</aop:aspect>
</aop:config>
</beans>

maven 依赖项:

  <dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>2.5.5</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>2.5.5</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjrt</artifactId>
<version>1.7.3</version>
</dependency>
<dependency>
<groupId>org.aspectj</groupId>
<artifactId>aspectjweaver</artifactId>
<version>1.7.3</version>
</dependency>
<dependency>
<groupId>org.apache.derby</groupId>
<artifactId>derby</artifactId>
<version>10.13.1.1</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>3.6.0.Final</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.8.2</version>
</dependency>
</dependencies>

编辑:

LoggingAspect 类:

  package com.logging;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.aspectj.lang.JoinPoint;

public class LoggingAspect {
private static final Logger LOGGER =
LogManager.getLogger(LoggingAspect.class);
public void logAround(JoinPoint aJoinPoint) {
LOGGER.info("aspects logging enabled");
}
}

最佳答案

是的,您的方面有问题。它实际上并没有调用检测代码。试试这个:

public void logAround(ProceedingJoinPoint aJoinPoint) { // <<-- don't forget to change the type to ProceedingJoinPoint
LOGGER.info("aspects logging enabled");
aJoinPoint.proceed(); // this will continue to the instrumented code
}

关于java - 使用 ApplicationContext 初始化 bean 时发生类转换异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/43710405/

24 4 0
Copyright 2021 - 2024 cfsdn All Rights Reserved 蜀ICP备2022000587号
广告合作:1813099741@qq.com 6ren.com