Unnecessary parameter name introspection for constructor-arg resolution (leading to LocalVariableTableParameterNameDiscoverer warnings)

[leonchen83]

after upgrade to springframework 6.0.2. we got following warnings

22-11-30 17:39:11.513 WARN [main LocalVariableTableParameterNameDiscoverer.inspectClass:123]Using deprecated '-debug' fallback for parameter name resolution. Compile the affected code with '-parameters' instead or avoid its introspection: org.jasypt.spring31.properties.EncryptablePropertyPlaceholderConfigurer
22-11-30 17:39:15.632 WARN [main LocalVariableTableParameterNameDiscoverer.inspectClass:123]Using deprecated '-debug' fallback for parameter name resolution. Compile the affected code with '-parameters' instead or avoid its introspection: org.jasypt.spring31.properties.EncryptablePropertyPlaceholderConfigurer
22-11-30 17:39:19.351 WARN [main LocalVariableTableParameterNameDiscoverer.inspectClass:123]Using deprecated '-debug' fallback for parameter name resolution. Compile the affected code with '-parameters' instead or avoid its introspection: org.eclipse.jetty.server.Server
22-11-30 17:39:19.394 WARN [main LocalVariableTableParameterNameDiscoverer.inspectClass:123]Using deprecated '-debug' fallback for parameter name resolution. Compile the affected code with '-parameters' instead or avoid its introspection: org.eclipse.jetty.server.HttpConnectionFactory
22-11-30 17:39:19.409 WARN [main LocalVariableTableParameterNameDiscoverer.inspectClass:123]Using deprecated '-debug' fallback for parameter name resolution. Compile the affected code with '-parameters' instead or avoid its introspection: org.eclipse.jetty.server.ServerConnector

all we source code already add compile args -parameters. I want to ask how to handle third party jar's compile args. and how to eliminate above warning

[jhoeller]

Why are those Jasypt/Jetty classes getting introspected in the first place? Do you have bean configuration that refers to their constructor parameter names or the like?

Generally speaking, Spring-driven parameter name introspection is only being triggered by actual demand at runtime. Some step has to trigger the introspection attempt through asking for a parameter name on a specific method/constructor. It would be very helpful to find out what it is in your scenario.

We intend to remove debug symbol introspection completely in 6.1, exclusively relying on -parameters. That's the main reason for that warn logging. Aside from missing -parameters, we also found quite a few places where parameter names were introspected but effectively not used - which is quite costly since we are unnecessarily parsing the class file for every affected class there. We'd like to identify and fix all such remaining cases.

[leonchen83]

@jhoeller
I create a simple project to reproduce our scenario.

please refer to spring-test

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:p="http://www.springframework.org/schema/p" xmlns:c="http://www.springframework.org/schema/c"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 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">
    
    <!-- server -->
    <bean id="jetty.server" class="org.eclipse.jetty.server.Server">
        <property name="stopAtShutdown" value="true"/>
        <property name="dumpAfterStart" value="false"/>
        <property name="dumpBeforeStop" value="false"/>
        <property name="connectors" ref="jetty.connectors"/>
    </bean>
    
    <util:list id="jetty.connectors" list-class="java.util.ArrayList">
        <bean id="jetty.connector.server" class="org.eclipse.jetty.server.ServerConnector">
            <constructor-arg index="0" ref="jetty.server"/>
            <constructor-arg index="1" ref="jetty.connections"/>
            <property name="port" value = "8080"/>
            <property name="host" value = "127.0.0.1"/>
            <property name="idleTimeout" value = "30000"/>
        </bean>
    </util:list>
    
    <util:list id="jetty.connections" list-class="java.util.ArrayList">
        <bean id="jetty.connection.http" class="org.eclipse.jetty.server.HttpConnectionFactory">
            <constructor-arg>
                <bean class="org.eclipse.jetty.server.HttpConfiguration">
                    <property name="securePort" value="8442"/><property name="secureScheme" value="https"/>
                    <property name="headerCacheSize" value="512"/><property name="outputBufferSize" value="32768"/>
                    <property name="sendDateHeader" value="false"/><property name="sendServerVersion" value="false"/>
                    <property name="requestHeaderSize" value="8192"/><property name="responseHeaderSize" value="8192"/>
                </bean>
            </constructor-arg>
        </bean>
    </util:list>
</beans>

[jhoeller]

It looks like the core bean factory is unnecessarily retrieving constructor parameter names during the constructor autowiring algorithm, despite no constructor argument names having been specified. That's a bug we're going to fix in 6.0.3.

Thanks for the configuration snippet! There is no need to change anything there as far as I can see. The warnings should disappear when running that same code on 6.0.3 then.

[jhoeller]

For the time being, you may simply disable the warn log category for org.springframework.core.LocalVariableTableParameterNameDiscoverer. There is unnecessary reading of class files in the meantime but otherwise no harm for your application.