Java 9迁移期间找不到不兼容的类型,等式约束和方法

Question

在将我们的一个项目迁移到Java 9(build 9 + 181)时,我遇到了一个特殊的问题,在类型推断和java模块相关的某些库中看起来像是一个不正确的实现.我使用的是dropwizard-core(1.1.0)和guice(4.1.0)配置如下:

public class CustomService extends io.dropwizard.Application<CustomServiceConfig> {

    public static void main(String[] args) throws Exception {
        new CustomService().run(args);
    }

    // other initializations

    @Override
    public void run(CustomServiceConfig config, io.dropwizard.setup.Environment environment) throws Exception {
        com.google.inject.Injector injector = createInjector(config, environment);
        environment.jersey().register(injector.getInstance(SomeResource.class)); //line 45
        environment.healthChecks().register("DBHealth", injector.getInstance(HealthCheck.class)); 
        environment.servlets().addFilter("Filter-Name", SomeFilter.class)
                .addMappingForUrlPatterns(EnumSet.allOf(DispatcherType.class), true, "/*");
    }


    private com.google.inject.Injector createInjector(CustomServiceConfig config, Environment environment) {
        return com.google.inject.Guice.createInjector(new CustomServiceModule(config, environment));
    }

}

---

public class CustomServiceModule extends com.google.inject.AbstractModule {
    private final CustomServiceConfig serviceConfig;
    private final Environment environment;

    public CustomServiceModule(CustomServiceConfig serviceConfig, Environment environment) {
        this.serviceConfig = serviceConfig;
        this.environment = environment;
    }

    @Override
    protected void configure() {
        bind(SomeInterface.class).to(SomeInterfaceImpl.class);
        ..
    }
}

---

使用以下组合,配置对我来说很好:

• Java 8 + Maven 3 +编译器插件3.6.1 [我们的原始设置]
• Java 9 + Maven 3 +编译器插件3.7.0(更新了命令行和maven配置)

但是当我切换到模块结构然后尝试编译由这些类组成的maven模块时,我在以下期间遇到这些错误mvn clean install:

[ERROR] ../service/service/CustomService.java:[45,29] incompatible types: inference variable T has incompatible bounds
    equality constraints: base.SomeResource
    upper bounds: java.lang.Class<?>,java.lang.Object

[ERROR] ../service/service/CustomService.java:[56,31]
no suitable method found for
addFilter(java.lang.String,java.lang.Class< SomeFilter >)
[ERROR]     method io.dropwizard.jetty.setup.ServletEnvironment.addFilter(java.lang.String,javax.servlet.Filter)
is not applicable
[ERROR]       (argument mismatch; java.lang.Class< SomeFilter > cannot be
converted to javax.servlet.Filter)

我不确定为什么会出现这些错误,以及它们是否与使用中的模块结构有关.

Q1.是否有任何类型推断相关的更改可能会影响maven编译与模块结构更改(如果可能),请记住使用的依赖项？

同时在迁移时,我主要使用IntelliJ建议的自动模块名来构造module-infoas:

module service {
//    Internal modules  which compile successfully
    requires model;
    requires util;

//    Dependent library modules
    requires httpcore;
    requires guice;
    requires guava;
    requires dropwizard.core;
    requires mongo.java.driver;
    requires org.apache.commons.lang3;
    requires javax.servlet.api;
}

Q2.如果这不是迁移时的回归问题,为什么这不会因我们之前的设置而失败？这是否也要求我们的服务中的代码更改,或者我们是否应该等待库移动到模块,如果这可能有帮助？

注意:尝试研究依赖版本和类实现的用法.它们在先前和当前设置中都相同.

如果我能提供任何进一步的信息,请告诉我.

---

更新:我能够在我创建的微服务示例中重现它,以将其与我项目的其余部分隔离开来.

Answer 1

从示例项目中我能够解决编译问题.方法中有2个例外com.SomeService#run.您的module-info.java中缺少模块,一旦添加这些模块,代码就应该编译.

requires dropwizard.jersey;
requires dropwizard.jetty;

JerseyEnvironment 来自 io.dropwizard:dropwizard-jersey:1.1.0

ServletEnvironment 来自 io.dropwizard:dropwizard-jetty:1.1.0

由于它们是不同的罐子,因此它们会输出不同的模块.因此,需要明确添加要求.没有module-info.java,您的代码工作正常,因为那时不使用模块系统.

我通过以下方式找到了解决方法:评论中提到的方法:

@Override
public void run(SomeServiceConfig config, Environment environment) throws Exception {
    Injector injector = Guice.createInjector(new SomeServiceModule());
    // Fix: Extract to variable to find Type of jersey and then find the module to add under requires
    JerseyEnvironment jersey = environment.jersey(); 
    jersey.register(injector.getInstance(SomeResource.class));
    // Fix 2: Same method as Fix 1
    ServletEnvironment servlets = environment.servlets();
    servlets.addFilter("Some-Filter", SomeFilter.class);
}