如果mvn测试，Janino找不到java.sql.PreparedStatement

Question

一个简单的单元测试(没有junit)会产生奇怪的异常。

import java.io.StringReader;
import java.sql.PreparedStatement;

import org.codehaus.janino.SimpleCompiler;

public class TestJanino {
    public void testJanino() throws Exception {
        PreparedStatement ps = null;
        String sampleClass = "import java.sql.PreparedStatement; public class Test{}";
        SimpleCompiler sc = new SimpleCompiler();
        sc.setParentClassLoader(getClass().getClassLoader());
        sc.cook("Test.java", new StringReader(sampleClass));
        System.out.println(sc.getBytecodes().size());
    }

    public static void main(String[] args) throws Exception {
        TestJanino d = new TestJanino();
        d.testJanino();
    }
}

信息是：

[INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ xx.xxx.server.nn ---
[WARNING] useSystemClassloader setting has no effect when not forking
[INFO] Surefire report directory: D:\workspace\XXXX\xx.xxx.server.nn\target\surefire-reports

-------------------------------------------------------
 T E S T S
-------------------------------------------------------
Running xx.xxx.server.nn.TestJanino
Tests run: 1, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 0.057 sec <<< FAILURE!
xx.xxx.server.nn.TestJanino.testJanino()  Time elapsed: 0.056 sec  <<< FAILURE!
org.codehaus.commons.compiler.CompileException: File 'Test.java', Line 1, Column 1: A class "java.sql.PreparedStatement" could not be found
        at org.codehaus.janino.UnitCompiler.compileError(UnitCompiler.java:12679)
        at org.codehaus.janino.UnitCompiler.getSingleTypeImport(UnitCompiler.java:10639)
        at org.codehaus.janino.UnitCompiler.checkForConflictWithSingleTypeImport(UnitCompiler.java:454)
        at org.codehaus.janino.UnitCompiler.compile2(UnitCompiler.java:410)
        at org.codehaus.janino.UnitCompiler.access$400(UnitCompiler.java:231)
        at org.codehaus.janino.UnitCompiler$2.visitPackageMemberClassDeclaration(UnitCompiler.java:391)
        at org.codehaus.janino.UnitCompiler$2.visitPackageMemberClassDeclaration(UnitCompiler.java:386)
        at org.codehaus.janino.Java$PackageMemberClassDeclaration.accept(Java.java:1692)
        at org.codehaus.janino.UnitCompiler.compile(UnitCompiler.java:386)
        at org.codehaus.janino.UnitCompiler.compile2(UnitCompiler.java:359)
        at org.codehaus.janino.UnitCompiler.access$000(UnitCompiler.java:231)
        at org.codehaus.janino.UnitCompiler$1.visitCompilationUnit(UnitCompiler.java:333)
        at org.codehaus.janino.UnitCompiler$1.visitCompilationUnit(UnitCompiler.java:330)
        at org.codehaus.janino.Java$CompilationUnit.accept(Java.java:367)
        at org.codehaus.janino.UnitCompiler.compileUnit(UnitCompiler.java:330)
        at org.codehaus.janino.SimpleCompiler.cook(SimpleCompiler.java:245)
        at org.codehaus.janino.SimpleCompiler.compileToClassLoader(SimpleCompiler.java:473)
        at org.codehaus.janino.SimpleCompiler.cook(SimpleCompiler.java:223)
        at org.codehaus.janino.SimpleCompiler.cook(SimpleCompiler.java:209)
        at xx.xxx.server.nn.TestJanino.testJanino(TestJanino.java:14)


Results :

Failed tests:   xx.xxx.server.nn.TestJanino.testJanino(): File 'Test.java', Line 1, Column 1: A class "java.sql.PreparedStatement" could not be found

Tests run: 1, Failures: 1, Errors: 0, Skipped: 0

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.738 s
[INFO] Finished at: 2021-12-14T07:52:08+01:00
[INFO] ------------------------------------------------------------------------

但是，如果我在不使用maven的情况下运行main，它将解析如下：

​

​

那件事怎么可能？

这是我的pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>xx.xxx</groupId>
    <version>xxx-SNAPSHOT</version>
    <properties>
        <forkMode>never</forkMode>
    </properties>
    <artifactId>xxx</artifactId>
    <dependencies>
        <dependency>
            <groupId>org.codehaus.janino</groupId>
            <artifactId>janino</artifactId>
            <version>3.1.6</version>
        </dependency>
    </dependencies>
</project>

Answer 1

我终于能够用Java 11和Maven 3.8重现您的问题。

正如问题注释中所指出的，这个问题似乎与Maven surefire插件没有使用系统类加载器这一事实有关。请考虑阅读相关文件。

您可以使用以下插件配置验证这一点：

<build>
    <plugins>
       <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-surefire-plugin</artifactId>
            <version>2.12.4</version>
            <configuration>
                <useSystemClassLoader>false</useSystemClassLoader>
            </configuration>
       </plugin>
    </plugins>
</build>

您没有显式地提供此配置，但正如Maven跟踪中所示：

...
[WARNING] useSystemClassloader setting has no effect when not forking
...

您没有使用分叉，这与pom.xml中提供的配置是一致的。

<properties>
    <forkMode>never</forkMode>
</properties>

为了解决这个问题，您可以删除该配置，并且测试将在没有进一步问题的情况下运行。

尽管如此，正如我在评论中所说的，我用不同的Maven版本和JDK 8测试了代码，它甚至可以将useSystemClassloader设置为false，所以我真的不能告诉您问题的确切原因，也许它可能与JDK版本有关，但也可能是Maven版本，甚至是Janino。