我可以拥有一个DefaultPasswordService 的实例并调用它的encryptPassword() 方法而不用担心线程安全问题吗？
文档没有说明这一点。
【问题讨论】：
标签： java multithreading thread-safety shiro
是的，你可以。您可以通过reading the source code 轻松验证这一点：
public String encryptPassword(Object plaintext) {
Hash hash = hashPassword(plaintext);
checkHashFormatDurability();
return this.hashFormat.format(hash);
}
可能发生的最糟糕的事情是checkHashFormatDurability 方法多次打印警告，但encryptPassword 方法将始终按预期工作。
但是请注意，DefaultPasswordService 本身不是线程安全的，无论是在构造之后还是在调用 setter 时。因此，在多线程中使用共享实例之前，您需要担心safe publication。
【讨论】：
它是安全的。我从以下测试类生成了一个跟踪记录所有方法调用和同时访问的字段：
public class TestShiro implements Runnable {
private static final DefaultPasswordService defaultPasswordService = new DefaultPasswordService();
protected void exec() {
/* calling
* defaultPasswordService.setHashFormat( new Shiro1CryptFormat() );
* will lead to a data race
*/
defaultPasswordService.encryptPassword( Thread.currentThread().getName());
}
private AtomicInteger threadCount = new AtomicInteger();
public void test() throws Exception
{
for(int i = 0; i < 8 ;i++)
{
Thread thread = new Thread(this, "First Test Thread " + i);
this.threadCount.incrementAndGet();
thread.start();
}
while( this.threadCount.get() > 0 )
{
Thread.sleep(1000);
}
Thread.sleep(10 * 1000);
}
public void run()
{
exec();
threadCount.decrementAndGet();
}
public static void main(String[] args) throws Exception
{
(new TestShiro()).test();
}
}
一个线程的 Trace 如下所示：
com.anarsoft.agent.regression.MultiThreadedOneInstanceTemplate.run
com.anarsoft.agent.regression.TestShiro.exec
org.apache.shiro.authc.credential.DefaultPasswordService.encryptPassword
org.apache.shiro.authc.credential.DefaultPasswordService.hashPassword
org.apache.shiro.authc.credential.DefaultPasswordService.createByteSource
org.apache.shiro.util.ByteSource$Util.bytes
org.apache.shiro.util.ByteSource$Util.isCompatible
org.apache.shiro.util.SimpleByteSource.<init>
org.apache.shiro.codec.CodecSupport.toBytes
org.apache.shiro.codec.CodecSupport.toBytes
org.apache.shiro.authc.credential.DefaultPasswordService.createHashRequest
org.apache.shiro.crypto.hash.SimpleHashRequest.<init>
org.apache.shiro.authc.credential.DefaultPasswordService.hashPassword
read from field org.apache.shiro.authc.credential.DefaultPasswordService.hashService from object 861842890
org.apache.shiro.crypto.hash.SimpleHashRequest.<init>
org.apache.shiro.crypto.hash.DefaultHashService.computeHash
org.apache.shiro.crypto.hash.DefaultHashService.getAlgorithmName
org.apache.shiro.crypto.hash.DefaultHashService.getHashAlgorithmName
read from field org.apache.shiro.crypto.hash.DefaultHashService.algorithmName from object 1033490990
org.apache.shiro.crypto.hash.DefaultHashService.getAlgorithmName
org.apache.shiro.crypto.hash.DefaultHashService.getIterations
org.apache.shiro.crypto.hash.DefaultHashService.getHashIterations
read from field org.apache.shiro.crypto.hash.DefaultHashService.iterations from object 1033490990
org.apache.shiro.crypto.hash.DefaultHashService.getIterations
org.apache.shiro.crypto.hash.DefaultHashService.getPublicSalt
org.apache.shiro.crypto.hash.DefaultHashService.getPrivateSalt
read from field org.apache.shiro.crypto.hash.DefaultHashService.privateSalt from object 1033490990
org.apache.shiro.crypto.hash.DefaultHashService.isGeneratePublicSalt
read from field org.apache.shiro.crypto.hash.DefaultHashService.generatePublicSalt from object 1033490990
org.apache.shiro.crypto.hash.DefaultHashService.getRandomNumberGenerator
read from field org.apache.shiro.crypto.hash.DefaultHashService.rng from object 1033490990
org.apache.shiro.crypto.hash.DefaultHashService.getPublicSalt
org.apache.shiro.crypto.SecureRandomNumberGenerator.nextBytes
org.apache.shiro.crypto.SecureRandomNumberGenerator.getDefaultNextBytesSize
read from field org.apache.shiro.crypto.SecureRandomNumberGenerator.defaultNextBytesSize from object 520016214
org.apache.shiro.crypto.SecureRandomNumberGenerator.nextBytes
org.apache.shiro.crypto.SecureRandomNumberGenerator.nextBytes
org.apache.shiro.crypto.SecureRandomNumberGenerator.nextBytes
read from field org.apache.shiro.crypto.SecureRandomNumberGenerator.secureRandom from object 520016214
org.apache.shiro.crypto.hash.DefaultHashService.getPrivateSalt
read from field org.apache.shiro.crypto.hash.DefaultHashService.privateSalt from object 1033490990
org.apache.shiro.crypto.SecureRandomNumberGenerator.nextBytes
org.apache.shiro.crypto.hash.DefaultHashService.combine
org.apache.shiro.crypto.hash.SimpleHash.<init>
org.apache.shiro.util.StringUtils.hasText
org.apache.shiro.util.StringUtils.hasLength
org.apache.shiro.crypto.hash.SimpleHash.convertSaltToBytes
org.apache.shiro.crypto.hash.SimpleHash.toByteSource
org.apache.shiro.crypto.hash.SimpleHash.convertSourceToBytes
org.apache.shiro.crypto.hash.SimpleHash.toByteSource
org.apache.shiro.crypto.hash.SimpleHash.hash
org.apache.shiro.crypto.hash.SimpleHash.hash
org.apache.shiro.crypto.hash.SimpleHash.getDigest
java.util.HashMap.getNode
read from field java.util.HashMap.table from object 832279283
java.util.HashMap.getNode
read from field java.util.HashMap$Node.hash from object 22805895
java.util.HashMap.getNode
read from field java.util.HashMap$Node.key from object 22805895
java.util.LinkedHashMap.get
read from field java.util.LinkedHashMap.accessOrder from object 832279283
java.util.LinkedHashMap.get
read from field java.util.HashMap$Node.value from object 22805895
java.util.HashMap.getNode
read from field java.util.HashMap.table from object 1924582348
java.util.HashMap.getNode
read from field java.util.HashMap$Node.hash from object 2097514481
java.util.HashMap.getNode
read from field java.util.HashMap$Node.key from object 2097514481
java.util.HashMap.get
read from field java.util.HashMap$Node.value from object 2097514481
org.apache.shiro.crypto.hash.SimpleHash.getDigest
org.apache.shiro.crypto.hash.SimpleHash.setIterations
org.apache.shiro.authc.credential.DefaultPasswordService.checkHashFormatDurability
org.apache.shiro.authc.credential.DefaultPasswordService.checkHashFormatDurability
read from field org.apache.shiro.authc.credential.DefaultPasswordService.hashFormatWarned from object 861842890
org.apache.shiro.authc.credential.DefaultPasswordService.checkHashFormatDurability
read from field org.apache.shiro.authc.credential.DefaultPasswordService.hashFormat from object 861842890
org.apache.shiro.authc.credential.DefaultPasswordService.encryptPassword
read from field org.apache.shiro.authc.credential.DefaultPasswordService.hashFormat from object 861842890
org.apache.shiro.authc.credential.DefaultPasswordService.checkHashFormatDurability
org.apache.shiro.crypto.hash.format.Shiro1CryptFormat.format
org.apache.shiro.util.SimpleByteSource.toBase64
org.apache.shiro.codec.Base64.encodeToString
org.apache.shiro.codec.Base64.encode
org.apache.shiro.codec.Base64.encode
org.apache.shiro.codec.CodecSupport.toString
org.apache.shiro.codec.CodecSupport.toString
org.apache.shiro.crypto.hash.SimpleHash.toBase64
org.apache.shiro.codec.Base64.encodeToString
org.apache.shiro.codec.Base64.encode
org.apache.shiro.codec.Base64.encode
org.apache.shiro.codec.CodecSupport.toString
org.apache.shiro.codec.CodecSupport.toString
com.anarsoft.agent.regression.MultiThreadedOneInstanceTemplate.run
read from field com.anarsoft.agent.regression.MultiThreadedOneInstanceTemplate.threadCount from object 1461149300
所以只有从创建 DefaultPasswordService 写入的字段中读取。在我的测试中，创建发生在主线程中。
【讨论】：
它是线程安全的，因为在加密过程中没有写入类成员。
从技术上讲，您确实需要确保在执行encryptPassword(...) 期间没有对setHashService 或setHashFormat 的调用。例如，调用 setHashService(null) 会导致 encryptPassword(...) 引发 NPE。
在实践中，这可能不是问题，因为在服务启动并运行后不太可能有理由更改 HashService 或 HashFormat。
【讨论】：