Spring IDREF用法
Spring IDREF用法
提问于 2013-01-30 23:07:35
我有一个定义如下的spring.xml：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd">
<beans>
<bean id="triangle" class="org.tutorial.spring.Triangle">
<property name="pointA">
<idref bean="pointA"/>
</property>
<property name="pointB" ref="pointB"/>
<property name="pointC" ref="pointC"/>
</bean>
<bean id="pointA" class="org.tutorial.spring.Point">
<property name="x" value="0"/>
<property name="y" value="0"/>
</bean>
<bean id="pointB" class="org.tutorial.spring.Point">
<property name="x" value="100"/>
<property name="y" value="200"/>
</bean>
<bean id="pointC" class="org.tutorial.spring.Point">
<property name="x" value="-100"/>
<property name="y" value="-200"/>
</bean>
</beans>Point类基本上是一个具有2个私有int成员的类。我的问题是我在IDREF上得到的错误如下：
Caused by: org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'java.lang.String' to required type 'org.tutorial.spring.Point' for property 'pointA';
nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [org.tutorial.spring.Point] for property 'pointA': no matching editors or conversion strategy found据我所知，IDREF (在上面的例子中)的目的是为了bean三角形而存在bean PointA (错误检查)。因此，我在IDREF元素中提供了bean PointA(string)的名称。为什么会出现上面的错误？
当我认为它只是通过提供名称来检查bean (PointA)的存在时，为什么它要尝试将字符串转换为Point？
我真的很困惑。请帮帮忙。谢谢。
回答 5
Stack Overflow用户
回答已采纳
发布于 2013-01-31 00:18:25
idref用于传递bean (即字符串)的名称(标识符)。
<idref bean="pointA">与字符串值pointA完全相同，不同之处在于如果没有定义这样的bean，Spring会报错。
详情请参见the Spring documentation。
要传递实际的bean，只需使用ref，就像对pointB和pointC所做的那样。
Stack Overflow用户
发布于 2013-08-31 02:17:29
idref元素只是将容器中另一个bean的id (字符串值-不是引用)传递给或元素的一种防错方法。
简单地说，idref元素用于传递字符串值，使用idref标记允许容器在部署时验证引用的命名bean是否实际存在。
考虑下面的例子
注意控制台中的输出，当我们调用secondBean.getSecondMessage()时，它的值是firstBean，它是使用idref属性设置的。
注意:元素带来价值的一个常见地方是在ProxyFactoryBean bean定义中AOP拦截器的配置中。在指定拦截器名称时使用元素可以防止拦截器id拼写错误。
Stack Overflow用户
发布于 2016-10-21 19:42:11
通过使用‘idref’标记，您可以在部署时验证引用的命名bean是否实际存在。
例如,
<bean id="paulo" class="com.sample.pojo.Author">
<property name="firstName" value="Paulo" />
<property name="lastName" value="Coelho" />
<property name="dateOfBirth" value="24 August 1947" />
<property name="country" value="India" />
</bean>如果您像下面这样定义验证器bean，Spring将在部署时验证ids为osho和Paulo的bean。如果在配置文件中没有找到任何bean，spring就会抛出BeanDefinitionStoreException。
<bean id="validatorBean" class="com.sample.test.BeansValidator">
<property name="author1">
<idref bean="osho" />
</property>
<property name="author2">
<idref bean="paulo" />
</property>
</bean>以下是完整的工作应用程序。
package com.sample.pojo;
public class Author {
private String firstName;
private String lastName;
private String dateOfBirth;
private String country;
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getDateOfBirth() {
return dateOfBirth;
}
public void setDateOfBirth(String dateOfBirth) {
this.dateOfBirth = dateOfBirth;
}
public String getCountry() {
return country;
}
public void setCountry(String country) {
this.country = country;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append("Author [firstName=").append(firstName).append(", lastName=").append(lastName)
.append(", dateOfBirth=").append(dateOfBirth).append(", country=").append(country).append("]");
return builder.toString();
}
}BeansValidator.java
package com.sample.test;
public class BeansValidator {
private String author1;
private String author2;
public String getAuthor1() {
return author1;
}
public void setAuthor1(String author1) {
this.author1 = author1;
}
public String getAuthor2() {
return author2;
}
public void setAuthor2(String author2) {
this.author2 = author2;
}
}myConfiguration.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"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="osho" class="com.sample.pojo.Author">
<property name="firstName" value="Osho" />
<property name="lastName" value="Jain" />
<property name="dateOfBirth" value="11 December 1931" />
<property name="country" value="India" />
</bean>
<bean id="paulo" class="com.sample.pojo.Author">
<property name="firstName" value="Paulo" />
<property name="lastName" value="Coelho" />
<property name="dateOfBirth" value="24 August 1947" />
<property name="country" value="India" />
</bean>
<bean id="validatorBean" class="com.sample.test.BeansValidator">
<property name="author1">
<idref bean="osho" />
</property>
<property name="author2">
<idref bean="paulo" />
</property>
</bean>
</beans>运行HelloWorld.java，你不会得到任何异常。
package com.sample.test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class HelloWorld {
public static void main(String args[]) {
ApplicationContext context = new ClassPathXmlApplicationContext(new String[] { "myConfiguration.xml" });
((ClassPathXmlApplicationContext) context).close();
}
}现在像下面这样更新myConfiguration.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"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<bean id="osho" class="com.sample.pojo.Author">
<property name="firstName" value="Osho" />
<property name="lastName" value="Jain" />
<property name="dateOfBirth" value="11 December 1931" />
<property name="country" value="India" />
</bean>
<bean id="paulo" class="com.sample.pojo.Author">
<property name="firstName" value="Paulo" />
<property name="lastName" value="Coelho" />
<property name="dateOfBirth" value="24 August 1947" />
<property name="country" value="India" />
</bean>
<bean id="validatorBean" class="com.sample.test.BeansValidator">
<property name="author1">
<idref bean="Krishna" />
</property>
<property name="author2">
<idref bean="paulo" />
</property>
</bean>
</beans>正如您看到的配置文件一样，validatorBean检查id为‘Krishna’的bean。
<bean id="validatorBean" class="com.sample.test.BeansValidator">
<property name="author1">
<idref bean="Krishna" />
</property>
<property name="author2">
<idref bean="paulo" />
</property>
</bean>由于id为‘Krishna’的bean不存在，您将在下面的错误中结束。
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'validatorBean' defined in class path resource [myConfiguration.xml]: Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanDefinitionStoreException: Invalid bean name 'Krishna' in bean reference for bean property 'author1'
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:751)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:861)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:541)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:93)
at com.sample.test.HelloWorld.main(HelloWorld.java:8)页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/14607142
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