Spring Boot集成PulsarClient遇DNS TTL访问权限错误求助

使用Java 20、Spring Boot 3.1.0、Pulsar 3.0.0组合初始化PulsarClient时，出现模块访问权限错误，具体信息如下：

依赖版本配置：

<properties>
    <java.version>20</java.version>
    <pulsar.version>3.0.0</pulsar.version>
    <spring.boot.version>3.1.0</spring.boot.version>
</properties>

初始化PulsarClient的配置类代码：

@Configuration
public class PulsarConfiguration {

    @Bean
    public PulsarClient pulsarClient() throws PulsarClientException {
        return PulsarClient.builder().serviceUrl("pulsar://localhost:6650").build();
    }
}

抛出的错误日志：

Cannot get DNS TTL settings from sun.net.InetAddressCachePolicy class

java.lang.IllegalAccessException: class org.apache.pulsar.common.util.netty.DnsResolverUtil cannot access class sun.net.InetAddressCachePolicy (in module java.base) because module java.base does not export sun.net to unnamed module @6069db50
    at java.base/jdk.internal.reflect.Reflection.newIllegalAccessException(Reflection.java:394) ~[na:na]
    at java.base/java.lang.reflect.AccessibleObject.checkAccess(AccessibleObject.java:709) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:569) ~[na:na]
    at org.apache.pulsar.common.util.netty.DnsResolverUtil.<clinit>(DnsResolverUtil.java:46) ~[pulsar-client-3.0.0.jar:3.0.0]
    at org.apache.pulsar.client.impl.ConnectionPool.createAddressResolver(ConnectionPool.java:159) ~[pulsar-client-3.0.0.jar:3.0.0]
    at org.apache.pulsar.client.impl.ConnectionPool.lambda$new$1(ConnectionPool.java:126) ~[pulsar-client-3.0.0.jar:3.0.0]
    at java.base/java.util.Optional.orElseGet(Optional.java:364) ~[na:na]
    at org.apache.pulsar.client.impl.ConnectionPool.<init>(ConnectionPool.java:126) ~[pulsar-client-3.0.0.jar:3.0.0]
    at org.apache.pulsar.client.impl.ConnectionPool.<init>(ConnectionPool.java:95) ~[pulsar-client-3.0.0.jar:3.0.0]
    at org.apache.pulsar.client.impl.ConnectionPool.<init>(ConnectionPool.java:90) ~[pulsar-client-3.0.0.jar:3.0.0]
    at org.apache.pulsar.client.impl.PulsarClientImpl.<init>(PulsarClientImpl.java:196) ~[pulsar-client-3.0.0.jar:3.0.0]
    at org.apache.pulsar.client.impl.PulsarClientImpl.<init>(PulsarClientImpl.java:153) ~[pulsar-client-3.0.0.jar:3.0.0]
    at org.apache.pulsar.client.impl.ClientBuilderImpl.build(ClientBuilderImpl.java:63) ~[pulsar-client-3.0.0.jar:3.0.0]
    at in.silentsudo.springbootmongodbdatagenerator.PulsarConfiguration.pulsarClient(PulsarConfiguration.java:16) ~[classes/:na]

拒绝降级方案，寻求其他解决途径。

方案1：添加JVM参数开放模块访问权限 #

启动应用时加入以下JVM参数，允许Pulsar客户端访问Java基础模块中的sun.net包：

--add-exports java.base/sun.net=ALL-UNNAMED

• 若使用Maven插件启动，在pom.xml的spring-boot-maven-plugin中配置：

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <jvmArguments>--add-exports java.base/sun.net=ALL-UNNAMED</jvmArguments>
    </configuration>
</plugin>

• 若使用IDEA启动，直接在Run/Debug配置的VM options中添加该参数。

方案2：升级Pulsar版本至3.1.0及以上 #

该问题已在Pulsar 3.1.0版本中修复，修改pom.xml中的Pulsar版本即可：

<properties>
    <java.version>20</java.version>
    <pulsar.version>3.1.0</pulsar.version>
    <spring.boot.version>3.1.0</spring.boot.version>
</properties>

升级后无需额外配置，客户端会自动使用兼容Java模块系统的DNS缓存策略获取方式。

方案3：自定义DNS解析器（进阶） #

通过PulsarClientBuilder指定自定义DNS解析器，绕过默认的DNS处理逻辑：

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Collections;
import org.apache.pulsar.client.api.DnsResolver;
import org.apache.pulsar.client.api.PulsarClient;
import org.apache.pulsar.client.api.PulsarClientException;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class PulsarConfiguration {

    @Bean
    public PulsarClient pulsarClient() throws PulsarClientException {
        return PulsarClient.builder()
                .serviceUrl("pulsar://localhost:6650")
                .dnsResolver((DnsResolver) host -> {
                    try {
                        return Collections.singletonList(InetAddress.getByName(host));
                    } catch (UnknownHostException e) {
                        throw new RuntimeException(e);
                    }
                })
                .build();
    }
}

这种方式需要自行实现DNS解析逻辑，适合有特殊DNS需求的场景。

内容的提问来源于stack exchange，提问作者silentsudo