错误：对于属性“吉他手”：找不到匹配的编辑器或转换策略答案

【问题标题】：Error: for property 'guitarist': no matching editors or conversion strategy found错误：对于属性“吉他手”：找不到匹配的编辑器或转换策略
【发布时间】：2021-09-05 18:50:06
【问题描述】：

This is the example I'm working on

问题是我从这段代码中得到错误，例如：

线程“main”中的异常 org.springframework.beans.factory.BeanCreationException：在类路径资源中定义名称为“documentaristOne”的 bean 创建时出错 .... 对于属性“guitarist”：找不到匹配的编辑器或转换策略在 org.springframework.beans.factory.support...

界面：

public interface Singer {
    public void sing();    
}

类：

public class GrammyGuitarist implements Singer{

@Override
public void sing() {

    System.out.println("sing: Gravity is working against me\n" +
            "And gravity wants to bring me down");
}

public void sing(Guitar guitar) {
    System.out.println("play: " + guitar.play());
}

public void talk(){
    System.out.println("talk");
}

}

public class Documentarist {

protected GrammyGuitarist guitarist;

public void execute() {
    guitarist.sing();
    guitarist.talk();
}

public void setGuitarist(GrammyGuitarist guitarist) {
    this.guitarist = guitarist;
}
}

public class ProxyFactoryBeanDemo {
public static void main(String... args) {
    GenericXmlApplicationContext ctx = new GenericXmlApplicationContext();
    ctx.load("spring/app-context-xml.xml");
    ctx.refresh();

    Documentarist documentaristOne = ctx.getBean("documentaristOne", Documentarist.class);
    Documentarist documentaristTwo = ctx.getBean("documentaristTwo", Documentarist.class);

    System.out.println("Documentarist One >>");
    documentaristOne.execute();

    System.out.println("\nDocumentarist Two >> ");
    documentaristTwo.execute();
}
}

app-xml 文件

<?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:p="http://www.springframework.org/schema/p"
       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="johnMayer" class="com.apress.prospring5.ch5.GrammyGuitarist"/>
    <bean id="advice" class="com.apress.prospring5.ch5.AuditAdvice"/>

    <bean id="documentaristOne" class="com.apress.prospring5.ch5.Documentarist"
          p:guitarist-ref="proxyOne"/>

    <bean id="proxyOne" class="org.springframework.aop.framework.ProxyFactoryBean"
          p:target-ref="johnMayer" p:interceptorNames-ref="interceptorAdviceNames"/>

    <util:list id="interceptorAdviceNames">
        <value>advice</value>
    </util:list>


    <bean id="documentaristTwo" class="com.apress.prospring5.ch5.Documentarist"
          p:guitarist-ref="proxyTwo"/>

    <bean id="proxyTwo" class="org.springframework.aop.framework.ProxyFactoryBean"
          p:target-ref="johnMayer" p:interceptorNames-ref="interceptorAdvisorNames">
    </bean>

    <util:list id="interceptorAdvisorNames">
        <value>advisor</value>
    </util:list>

    <bean id="advisor" class="org.springframework.aop.support.DefaultPointcutAdvisor"
          p:advice-ref="advice">
        <property name="pointcut">
            <bean class="org.springframework.aop.aspectj.AspectJExpressionPointcut"
                  p:expression="execution(* sing*(..))"/>
        </property>
    </bean>

</beans>

正如我所见，问题在于尝试初始化 GenericXmlApplicationContext 在 app-xml 中的行：

<bean id="documentaristOne" class="com.apress.prospring5.ch5.Documentarist"
      p:guitarist-ref="proxyOne"/>

尝试创建 Documentarist 的 documentaristOne 实例，但对于属性 guitarist 我们不提供 GrammyGuitarist 的 bean 实例> 而是一个代理。是的，proxyOne 通过“johnMayer”引用了 GrammyGuitarist：

<bean id="proxyOne" class="org.springframework.aop.framework.ProxyFactoryBean"
      p:target-ref="johnMayer" p:interceptorNames-ref="interceptorAdviceNames"/>

但正如我所见，JAVA/Spring 不想接受它。是否有可能以某种方式将类型代理转换为目标类型？如果没有，那要怎么做才能使这段代码正常工作？

下面的完整堆栈：

 org.springframework.context.support.AbstractApplicationContext refresh
WARNING: Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'documentaristOne' defined in class path resource [ch5/ProxyFactoryBeanDemo/app-context-xml.xml]: Initialization of bean failed; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'com.sun.proxy.$Proxy7 implementing ch5.ProxyFactoryBeanDemo.Singer,org.springframework.aop.SpringProxy,org.springframework.aop.framework.Advised,org.springframework.core.DecoratingProxy' to required type 'ch5.ProxyFactoryBeanDemo.GrammyGuitarist' for property 'guitarist'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'com.sun.proxy.$Proxy7 implementing ch5.ProxyFactoryBeanDemo.Singer,org.springframework.aop.SpringProxy,org.springframework.aop.framework.Advised,org.springframework.core.DecoratingProxy' to required type 'ch5.ProxyFactoryBeanDemo.GrammyGuitarist' for property 'guitarist': no matching editors or conversion strategy found
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'documentaristOne' defined in class path resource [ch5/ProxyFactoryBeanDemo/app-context-xml.xml]: Initialization of bean failed; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'com.sun.proxy.$Proxy7 implementing ch5.ProxyFactoryBeanDemo.Singer,org.springframework.aop.SpringProxy,org.springframework.aop.framework.Advised,org.springframework.core.DecoratingProxy' to required type 'ch5.ProxyFactoryBeanDemo.GrammyGuitarist' for property 'guitarist'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'com.sun.proxy.$Proxy7 implementing ch5.ProxyFactoryBeanDemo.Singer,org.springframework.aop.SpringProxy,org.springframework.aop.framework.Advised,org.springframework.core.DecoratingProxy' to required type 'ch5.ProxyFactoryBeanDemo.GrammyGuitarist' for property 'guitarist': no matching editors or conversion strategy found
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:603)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:879)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550)
    at ch5.ProxyFactoryBeanDemo.ProxyFactoryBeanDemo.main(ProxyFactoryBeanDemo.java:14)
Caused by: org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'com.sun.proxy.$Proxy7 implementing ch5.ProxyFactoryBeanDemo.Singer,org.springframework.aop.SpringProxy,org.springframework.aop.framework.Advised,org.springframework.core.DecoratingProxy' to required type 'ch5.ProxyFactoryBeanDemo.GrammyGuitarist' for property 'guitarist'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'com.sun.proxy.$Proxy7 implementing ch5.ProxyFactoryBeanDemo.Singer,org.springframework.aop.SpringProxy,org.springframework.aop.framework.Advised,org.springframework.core.DecoratingProxy' to required type 'ch5.ProxyFactoryBeanDemo.GrammyGuitarist' for property 'guitarist': no matching editors or conversion strategy found
    at org.springframework.beans.AbstractNestablePropertyAccessor.convertIfNecessary(AbstractNestablePropertyAccessor.java:590)
    at org.springframework.beans.AbstractNestablePropertyAccessor.convertForProperty(AbstractNestablePropertyAccessor.java:604)
    at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:219)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.convertForProperty(AbstractAutowireCapableBeanFactory.java:1748)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1704)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1444)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:594)
    ... 9 more
Caused by: java.lang.IllegalStateException: Cannot convert value of type 'com.sun.proxy.$Proxy7 implementing ch5.ProxyFactoryBeanDemo.Singer,org.springframework.aop.SpringProxy,org.springframework.aop.framework.Advised,org.springframework.core.DecoratingProxy' to required type 'ch5.ProxyFactoryBeanDemo.GrammyGuitarist' for property 'guitarist': no matching editors or conversion strategy found
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:262)
    at org.springframework.beans.AbstractNestablePropertyAccessor.convertIfNecessary(AbstractNestablePropertyAccessor.java:585)
    ... 15 more
Command execution failed.
org.apache.commons.exec.ExecuteException: Process exited with an error: 1 (Exit value: 1)
    at org.apache.commons.exec.DefaultExecutor.executeInternal (DefaultExecutor.java:404)
    at org.apache.commons.exec.DefaultExecutor.execute (DefaultExecutor.java:166)
    at org.codehaus.mojo.exec.ExecMojo.executeCommandLine (ExecMojo.java:764)
    at org.codehaus.mojo.exec.ExecMojo.executeCommandLine (ExecMojo.java:711)
    at org.codehaus.mojo.exec.ExecMojo.execute (ExecMojo.java:289)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
    at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
    at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
    at org.apache.maven.cli.MavenCli.execute (MavenCli.java:957)
    at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:289)
    at org.apache.maven.cli.MavenCli.main (MavenCli.java:193)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:64)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:564)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)

【问题讨论】：

您能否发布完整的错误堆栈跟踪，而不是其中的一些...？
我已经添加了完整的堆栈。可以看看吗？
您还有一个接口Singer，在您发布的代码中没有使用，但是在您发布的Failed to convert property value of type 'com.sun.proxy.$Proxy7 implementing ch5.ProxyFactoryBeanDemo.Singer... 的堆栈跟踪中提到了它。您确定发布的代码是您要运行的代码吗？
GrammyGuitarist 实现了它。我编辑了，不知道为什么错过了。
我克隆了示例存储库并运行了应用程序。它工作得很好。您必须更改某些内容才能破坏它。

标签： java spring aop

【解决方案1】：

根本原因是，如果目标类实现了接口，则 Spring Core（不是 Spring Boot）默认创建 JDK 代理。对于您尝试修改的 ProxyFactoryBean 示例也是如此。即，一旦您使GrammyGuitarist 实现Singer，您将不再获得CGLIB 代理而是JDK 代理。 JDK 代理不是GrammyGuitarist 的子类，这意味着它不能强制转换为该类，但代码和配置显式引用该类，而不仅仅是Singer。因此，

要么你需要使bean类型Singer
或者您将 Spring 配置为使用代理工厂 bean 在 <beans> 部分中使用 <aop:aspectj-autoproxy proxy-target-class="true"/> 和在两个 bean 配置中使用 p:proxyTargetClass="true" 创建 CGLIB 代理。

我正在向您展示如何更改XML configuration。

这是差异：

diff --git a/chapter05/proxyfactorybean/src/main/java/com/apress/prospring5/ch5/GrammyGuitarist.java b/chapter05/proxyfactorybean/src/main/java/com/apress/prospring5/ch5/GrammyGuitarist.java
--- a/chapter05/proxyfactorybean/src/main/java/com/apress/prospring5/ch5/GrammyGuitarist.java   (revision Staged)
+++ b/chapter05/proxyfactorybean/src/main/java/com/apress/prospring5/ch5/GrammyGuitarist.java   (date 1630836290986)
@@ -1,11 +1,12 @@
 package com.apress.prospring5.ch5;
 
 import com.apress.prospring5.ch2.common.Guitar;
+import com.apress.prospring5.ch2.common.Singer;
 
 /**
  * Created by iuliana.cosmina on 4/9/17.
  */
-public class GrammyGuitarist {
+public class GrammyGuitarist implements Singer {
    public void sing() {
        System.out.println("sing: Gravity is working against me\n" +
                "And gravity wants to bring me down");
diff --git a/chapter05/proxyfactorybean/src/main/resources/spring/app-context-xml.xml b/chapter05/proxyfactorybean/src/main/resources/spring/app-context-xml.xml
--- a/chapter05/proxyfactorybean/src/main/resources/spring/app-context-xml.xml  (revision Staged)
+++ b/chapter05/proxyfactorybean/src/main/resources/spring/app-context-xml.xml  (date 1630838376150)
@@ -2,12 +2,17 @@
 
 <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"
        xmlns:p="http://www.springframework.org/schema/p"
        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">
+        http://www.springframework.org/schema/util/spring-util.xsd
+        http://www.springframework.org/schema/aop
+        http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">
+
+    <aop:aspectj-autoproxy proxy-target-class="true"/>
 
     <bean id="johnMayer" class="com.apress.prospring5.ch5.GrammyGuitarist"/>
     <bean id="advice" class="com.apress.prospring5.ch5.AuditAdvice"/>
@@ -16,7 +21,8 @@
           p:guitarist-ref="proxyOne"/>
 
     <bean id="proxyOne" class="org.springframework.aop.framework.ProxyFactoryBean"
-          p:target-ref="johnMayer" p:interceptorNames-ref="interceptorAdviceNames"/>
+          p:target-ref="johnMayer" p:interceptorNames-ref="interceptorAdviceNames"
+          p:proxyTargetClass="true"/>
 
     <util:list id="interceptorAdviceNames">
         <value>advice</value>
@@ -27,7 +33,8 @@
           p:guitarist-ref="proxyTwo"/>
 
     <bean id="proxyTwo" class="org.springframework.aop.framework.ProxyFactoryBean"
-          p:target-ref="johnMayer" p:interceptorNames-ref="interceptorAdvisorNames">
+          p:target-ref="johnMayer" p:interceptorNames-ref="interceptorAdvisorNames"
+          p:proxyTargetClass="true">
     </bean>
 
     <util:list id="interceptorAdvisorNames">

这是完整的 XML 配置：

<?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"
       xmlns:p="http://www.springframework.org/schema/p"
       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
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">

    <aop:aspectj-autoproxy proxy-target-class="true"/>

    <bean id="johnMayer" class="com.apress.prospring5.ch5.GrammyGuitarist"/>
    <bean id="advice" class="com.apress.prospring5.ch5.AuditAdvice"/>

    <bean id="documentaristOne" class="com.apress.prospring5.ch5.Documentarist"
          p:guitarist-ref="proxyOne"/>

    <bean id="proxyOne" class="org.springframework.aop.framework.ProxyFactoryBean"
          p:target-ref="johnMayer" p:interceptorNames-ref="interceptorAdviceNames"
          p:proxyTargetClass="true"/>

    <util:list id="interceptorAdviceNames">
        <value>advice</value>
    </util:list>


    <bean id="documentaristTwo" class="com.apress.prospring5.ch5.Documentarist"
          p:guitarist-ref="proxyTwo"/>

    <bean id="proxyTwo" class="org.springframework.aop.framework.ProxyFactoryBean"
          p:target-ref="johnMayer" p:interceptorNames-ref="interceptorAdvisorNames"
          p:proxyTargetClass="true">
    </bean>

    <util:list id="interceptorAdvisorNames">
        <value>advisor</value>
    </util:list>

    <bean id="advisor" class="org.springframework.aop.support.DefaultPointcutAdvisor"
          p:advice-ref="advice">
        <property name="pointcut">
            <bean class="org.springframework.aop.aspectj.AspectJExpressionPointcut"
                  p:expression="execution(* sing*(..))"/>
        </property>
    </bean>

</beans>

【讨论】：

我认为设置p:proxyTargetClass="true" 就足够了，不需要aop namespace。至少这对我有用。 Ref: If the proxyTargetClass property of the ProxyFactoryBean has been set to true, then a CGLIB-based proxy will be created.。 ----- （另外，尽量不要直接在这个github项目上运行代码。创建自己的项目并将必要的文件复制到自己的项目中。gitbub的原始项目只是不断抛出错误。）
对不起，但我当然在 GitHub 上修复了该项目，因为这是 OP 询问的内容。我完全按照这里的解释修复了它。它可以工作并且不会对我的 PR 抛出任何错误。如果你的经历有任何不同，要么你有另一个项目，要么没有按照我的指示。所以你的评论不是很有帮助，因为我的回答是正确的。我没有猜测，但我尝试过。我不必像你一样说“我认为”。就像我说的那样，效果很好。

【解决方案2】：

我相信你必须让spring beans知道你正在使用哪些组件。尝试在 Documentarist GrammyGuitarist 类初始化上方添加 @Component() 注释

【讨论】：

嗯...不，它没有帮助。但最有趣的是它如何为其他人工作？我的意思是这段代码来自书本，应该可以工作。