从遗留代码迁移到Java 11的问题

Question

我们正在迁移我们的旧代码，实际上是相当旧的Java 11。我在编译其中一个类时遇到问题。示例代码如下：

package XXXX;

import java.lang.ref.*;
import sun.security.action.*;
import java.security.*;
import java.io.*;

class Converters
{
    private static Object lock;
    private static String converterPackageName;
    private static String defaultEncoding;
    public static final int BYTE_TO_CHAR = 0;
    public static final int CHAR_TO_BYTE = 1;
    private static final String[] converterPrefix;
    private static SoftReference[] classCache;
    static /* synthetic */ Class class$sun$io$Converters;

    private static String getConverterPackageName() {
        final String converterPackageName = Converters.converterPackageName;
        if (converterPackageName != null) {
            return converterPackageName;
        }
        String converterPackageName2 = AccessController.doPrivileged((PrivilegedAction<String>)new GetPropertyAction("file.encoding.pkg"));
        if (converterPackageName2 != null) {
            Converters.converterPackageName = converterPackageName2;
        }
        else {
            converterPackageName2 = "sun.io";
        }
        return converterPackageName2;
    }

    private static Class getConverterClass(final int n, final String s) throws UnsupportedEncodingException {
        String aliasName = null;
        if (!s.equals("ISO8859_1")) {
            if (s.equals("8859_1")) {
                aliasName = "ISO8859_1";
            }
            else if (s.equals("ISO8859-1")) {
                aliasName = "ISO8859_1";
            }
            else if (s.equals("646")) {
                aliasName = "ASCII";
            }
            else {
                aliasName = CharacterEncoding.aliasName(s);
            }
        }
        if (aliasName == null) {
            aliasName = s;
        }
        try {
            return Class.forName(getConverterPackageName() + "." + Converters.converterPrefix[n] + aliasName);
        }
        catch (ClassNotFoundException ex) {
            throw new UnsupportedEncodingException(aliasName);
        }
    }

    private static Object newConverter(final String s, final Class clazz) throws UnsupportedEncodingException {
        try {
            return clazz.newInstance();
        }
        catch (InstantiationException ex) {
            throw new UnsupportedEncodingException(s);
        }
        catch (IllegalAccessException ex2) {
            throw new UnsupportedEncodingException(s);
        }
    }

    static Object newConverter(final int n, final String s) throws UnsupportedEncodingException {
        final Class converterClass;
        synchronized (Converters.lock) {
            converterClass = getConverterClass(n, s);
        }
        return newConverter(s, converterClass);
    }

    private static Class getDefaultConverterClass(final int n) {
        boolean b = false;
        final SoftReference softReference = Converters.classCache[n];
        if (softReference != null) {
            final Class clazz = softReference.get();
            if (clazz != null) {
                return clazz;
            }
            Converters.classCache[n] = null;
        }
        String defaultEncoding = Converters.defaultEncoding;
        if (Converters.defaultEncoding != null) {
            b = true;
        }
        else {
            defaultEncoding = AccessController.doPrivileged((PrivilegedAction<String>)new GetPropertyAction("file.encoding"));
            if (defaultEncoding != null) {
                Converters.defaultEncoding = defaultEncoding;
                b = true;
            }
            else {
                defaultEncoding = "ISO8859_1";
            }
        }
        Class clazz2;
        try {
            clazz2 = getConverterClass(n, defaultEncoding);
            if (b) {
                Converters.classCache[n] = new SoftReference(clazz2);
            }
        }
        catch (UnsupportedEncodingException ex) {
            try {
                clazz2 = getConverterClass(n, "ISO8859_1");
            }
            catch (UnsupportedEncodingException ex2) {
                throw new InternalError("Cannot find default " + Converters.converterPrefix[n] + " converter class");
            }
        }
        return clazz2;
    }

    static Object newDefaultConverter(final int n) {
        final Class defaultConverterClass;
        synchronized (Converters.lock) {
            defaultConverterClass = getDefaultConverterClass(n);
        }
        try {
            return newConverter("", defaultConverterClass);
        }
        catch (UnsupportedEncodingException ex) {
            throw new InternalError("Cannot instantiate default converter class " + defaultConverterClass.getName());
        }
    }

    static /* synthetic */ Class class$(final String s) {
        try {
            return Class.forName(s);
        }
        catch (ClassNotFoundException ex) {
            throw new NoClassDefFoundError(ex.getMessage());
        }
    }

    static {
        Converters.lock = ((Converters.class$sun$io$Converters == null) ? (Converters.class$sun$io$Converters = class$("sun.io.Converters")) : Converters.class$sun$io$Converters);
        Converters.converterPackageName = null;
        Converters.defaultEncoding = null;
        converterPrefix = new String[] { "ByteToChar", "CharToByte" };
        Converters.classCache = new SoftReference[2];
    }
}

在使用javac Converter.java编译它时，我得到以下错误：

import sun.security.action.*;
                   ^
  (package sun.security.action is declared in module java.base, which does not export it to the unnamed module)
Converters.java:47: error: cannot find symbol
                aliasName = CharacterEncoding.aliasName(s);
                            ^
  symbol:   variable CharacterEncoding
  location: class Converters
Converters.java:85: error: incompatible types: Object cannot be converted to Class
            final Class clazz = softReference.get();
                                                 ^
Note: Converters.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: Converters.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
3 errors

我尝试使用--add--export java.base/sun.security=All-UNNAMED导出它，但它仍然抛出错误。

有什么帮助吗？还想知道有没有其他方法来删除这个旧的旧代码与新的。

Answer 1

正如所指出的，这些是不应该直接使用的内部类。如果重构超出了范围，你应该使用--add-export，这应该是可行的！

您的--add-export参数是错误的。您需要使用正确的包来导出(在本例中为sun.security.action)和模块的名称(如果不使用模块，则全部为未命名，全部使用大写字母 !)。

所以这应该是--add-exports java.base/sun.security.action=ALL-UNNAMED

来自javac的文档：

--add-exports module/ package = other-module (，other- module )*指定当other-module的值为all - unnamed时，将包视为从其定义模块导出到其他模块或导出到所有未命名模块。

Answer 2

从Java9开始，JDK的大多数内部API都是are inaccessible at compile time的(将来，它们在运行时也将不可访问)。sun.security.action是一个内部包，所以你应该避免使用它。在您的示例中，您可以简单地删除new GetPropertyAction("file.encoding.pkg")并将其替换为一个lambda：

AccessController.doPrivileged((PrivilegedAction<Object>) () -> System.getProperty("prop"));