spring在构造器注入时报错,类型不匹配

====================================>User.java

public class User {

private Integer id;

private String name;

private Integer age;

 

public User(){}

public User(Integer id, String name, Integer age) {

super();

this.id = id;

this.name = name;

this.age = age;

}

 

public Integer getId() {

return id;

}

//setter and getter method ......

}

===================================================>Test.java

@org.junit.Test

public void testCase(){

ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

User user = (User)context.getBean("user");

System.out.println(user.getId()+":"+user.getName()+":"+user.getAge());

}

=====================================>applicationContext.xml

<bean id="user" class="com.ustcinfo.entity.User">

<constructor-arg index="0" type="int">

<value>1</value>

</constructor-arg>

<constructor-arg index="1" type="java.lang.String">

<value>scott</value>

</constructor-arg>

<constructor-arg index="2" type="java.lang.Integer">

<value>30</value>

</constructor-arg>

</bean>

用set方式不会报错,但是用构造器缺报错了:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'user' defined in class path resource [applicationContext.xml]: Could not resolve matching constructor (hint: specify index/type/name arguments for simple parameters to avoid type ambiguities)

at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:250)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1049)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:953)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:490)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:461)

at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:295)

at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:223)

at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)

at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)

at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:607)

at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:932)

at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:479)

at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)

at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)

at com.ustcinfo.entity.Test.testCase(Test.java:11)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:606)

at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)

at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)

at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)

at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)

at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)

at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)

at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)

at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)

at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)

at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)

at org.junit.runners.ParentRunner.run(ParentRunner.java:309)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:49)

at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

======================================>解决方案

看到红色加粗字体没?注意将type属性删除,只留一个index属性也是可以的(构造函数非重载的情况下),当然不删除最好,避免重载时出错,最好的解决办法是index和type同时配置。下面我来解释下为何添加上type属性后报错:注意我的实体类User中属性id是Integer类型,而applicationContext.xml中配置的是int,所以解决办法有两种,其一,将User中id类型改为int类型,其二,或者改applicationContext.xml配置为type="java.lang.Integer"

无人驾驶Autoware导读 认知有限,望大家多多包涵,有什么问题也希望能够与大家多交流,共同成长!本文先对无人驾驶Autoware介绍做个简单的介绍,具体内容后续再更,其他模块可以参考去我其他文章提示:以下是本篇文章正文内容。 阅读详情

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Spring 注入方式有三中 1.setter注入 2.构造器注入 3.基于注解的注入 1.setter注入 在InjectionServiceImple 中有 变量 injectionDao 并有其的set方法 还有一点需要注意:如果通过set方法注入属性,那么spring会通过默认的空参构造方法来实例化对象,所以如果在类中写了一个带有参数的构造方法,一定要把空参数的构造方法写上,否则spring没有办法实例化对象,导致报错。 2.构造器注入 注意:配置文件中的nam.

Imzhipo的博客 8702

Spring的三种注入方式(为什么推荐构造器注入?)

Spring有三种注入方式,分别是——这种方式是最常用的,我们可以使用或者是进行注入使用方式是最简单,但是也是最不推荐的!要使用也是推荐使用!@Resource和@Autowired的区别。

金鳞踏雨 2073

Spring为什么建议构造器注入?

本章的内容主要是想探讨我们在进行Spring 开发过程当中,关于依赖注入的几个知识点。感兴趣的读者可以先看下以下问题:@Autowired, @Resource, @Inject 三个注解的区别当你在使用@Autowired时,是否有出现过Field injection is not recommended的警告?你知道这是为什么吗?Spring 依赖注入有哪几种方式?官方是怎么建议使用的呢?如果你对上述问题都了解,那我个人觉得你的开发经验应该是不错的👍。

2501_92608043的博客 826

Spring为何禁用@Autowired字段注入?构造器注入的8大优势与终极实践

你还在用@Autowired字段注入?别骗自己了,那不是依赖注入,是依赖赌博!Spring早就不推荐了,你却还在写“运行时才报NPE”的代码,测试还得靠ReflectionTestUtils当保姆?本文撕开字段注入的温柔面纱,用Mermaid图解它的“残缺出生”,对比构造器注入如何让对象一出生就完整、不可变、可测试。你以为Spring能帮你解决循环依赖?不,它只是在偷偷擦屁股。真正的绅士,依赖全写在构造器里,final字段稳如老狗,测试一行new搞定。Lombok省事,但别偷懒——代码的健壮性,从拒绝字段注

m0_72340523的博客 996

为什么IDEA和Spring都不推荐使用@Autowired注入

为什么不推荐使用@Autowired

ZULJ131的博客 3130

spring default-autowire 构造器和set属性注入行为

XML 时代的:通过集中配置定义全局注入规则,但灵活性低。现代 Spring Boot:使用注解(@Autowired@Qualifier)实现更精确的注入控制,完全取代 XML 配置方式。构造器注入是当前的首选方案。

lanwp5302的博客 938

尽量使用构造器/setter注入@RequiredArgsConstructor而不推荐使用字段注入@Resoucre/@Autowired的原因

idea会发现spring并不推荐使用 原因:注入失败的话不会报错提示,容易出现空指针 spring推荐的写法 1.构造器注入 @Slf4j @RestController @RequestMapping("point") public class PointController { private final PointBiz1 pointBiz1; private final PointBiz2 pointBiz1; @Autowired public Po

Koikoi12的博客 4721
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