如何将对象序列化为字符串 [英] How to serialize an object into a string

问题描述

我能够将一个对象序列化为一个文件然后再次恢复它，如下一个代码片段所示。我想将对象序列化为字符串并存储到数据库中。任何人都可以帮助我吗？

I am able to serialize an object into a file and then restore it again as is shown in the next code snippet. I would like to serialize the object into a string and store into a database instead. Can anyone help me?

LinkedList<Diff_match_patch.Patch> patches = // whatever...
FileOutputStream fileStream = new FileOutputStream("foo.ser");
ObjectOutputStream os = new ObjectOutputStream(fileStream);
os.writeObject(patches1);
os.close();

FileInputStream fileInputStream = new FileInputStream("foo.ser");
ObjectInputStream oInputStream = new ObjectInputStream(fileInputStream);
Object one = oInputStream.readObject();
LinkedList<Diff_match_patch.Patch> patches3 = (LinkedList<Diff_match_patch.Patch>) one;
os.close();

推荐答案

塞尔吉奥：

您应该使用 BLOB 。使用JDBC非常简单。

You should use BLOB. It is pretty straighforward with JDBC.

您发布的第二个代码的问题是编码。您还应该对字节进行编码以确保它们都不会失败。

The problem with the second code you posted is the encoding. You should additionally encode the bytes to make sure none of them fails.

如果您仍想将其写入字符串，则可以使用 java.util.Base64 。

If you still want to write it down into a String you can encode the bytes using java.util.Base64.

仍然应该使用CLOB作为数据类型，因为您不知道序列化数据的长度。

Still you should use CLOB as data type because you don't know how long the serialized data is going to be.

以下是如何使用它的示例。

Here is a sample of how to use it.

import java.util.*;
import java.io.*;

/** 
 * Usage sample serializing SomeClass instance 
 */
public class ToStringSample {

    public static void main( String [] args )  throws IOException,
                                                      ClassNotFoundException {
        String string = toString( new SomeClass() );
        System.out.println(" Encoded serialized version " );
        System.out.println( string );
        SomeClass some = ( SomeClass ) fromString( string );
        System.out.println( "\n\nReconstituted object");
        System.out.println( some );


    }

    /** Read the object from Base64 string. */
   private static Object fromString( String s ) throws IOException ,
                                                       ClassNotFoundException {
        byte [] data = Base64.getDecoder().decode( s );
        ObjectInputStream ois = new ObjectInputStream( 
                                        new ByteArrayInputStream(  data ) );
        Object o  = ois.readObject();
        ois.close();
        return o;
   }

    /** Write the object to a Base64 string. */
    private static String toString( Serializable o ) throws IOException {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream( baos );
        oos.writeObject( o );
        oos.close();
        return Base64.getEncoder().encodeToString(baos.toByteArray()); 
    }
}

/** Test subject. A very simple class. */ 
class SomeClass implements Serializable {

    private final static long serialVersionUID = 1; // See Nick's comment below

    int i    = Integer.MAX_VALUE;
    String s = "ABCDEFGHIJKLMNOP";
    Double d = new Double( -1.0 );
    public String toString(){
        return  "SomeClass instance says: Don't worry, " 
              + "I'm healthy. Look, my data is i = " + i  
              + ", s = " + s + ", d = " + d;
    }
}

输出：

C:\samples>javac *.java

C:\samples>java ToStringSample
Encoded serialized version
rO0ABXNyAAlTb21lQ2xhc3MAAAAAAAAAAQIAA0kAAWlMAAFkdAASTGphdmEvbGFuZy9Eb3VibGU7T
AABc3QAEkxqYXZhL2xhbmcvU3RyaW5nO3hwf////3NyABBqYXZhLmxhbmcuRG91YmxlgLPCSilr+w
QCAAFEAAV2YWx1ZXhyABBqYXZhLmxhbmcuTnVtYmVyhqyVHQuU4IsCAAB4cL/wAAAAAAAAdAAQQUJ
DREVGR0hJSktMTU5PUA==


Reconstituted object
SomeClass instance says: Don't worry, I'm healthy. Look, my data is i = 2147483647, s = ABCDEFGHIJKLMNOP, d = -1.0

注意：对于Java 7及更早版本，您可以看到原始在此处回答

NOTE: for Java 7 and earlier you can see the original answer here

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