如何将对象序列化为字符串

问题

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。谁能帮我?

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();

#1 热门回答(251 赞)

塞尔吉奥:

你应该使用BLOB。使用JDBC非常简单。

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

如果你仍想将其写入String,则可以使用java.util.Base64对字节进行编码。

仍然应该使用CLOB作为数据类型,因为你不知道序列化数据将会持续多长时间。

以下是如何使用它的示例。

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,你可以看到原始的889103979


#2 热门回答(11 赞)

如何将数据写入ByteArrayOutputStream而不是FileOutputStream?

否则,你可以使用XMLEncoder序列化对象,保留XML,然后通过XMLDecoder反序列化。


#3 热门回答(7 赞)

感谢你的快速回复。我会立即给予一些投票,以表示你的帮助。我根据你的答案在我看来编写了最好的解决方案。

LinkedList<Patch> patches1 = diff.patch_make(text2, text1);
try {
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    ObjectOutputStream os = new ObjectOutputStream(bos);
    os.writeObject(patches1);
    String serialized_patches1 = bos.toString();
    os.close();


    ByteArrayInputStream bis = new ByteArrayInputStream(serialized_patches1.getBytes());
    ObjectInputStream oInputStream = new ObjectInputStream(bis);
    LinkedList<Patch> restored_patches1 = (LinkedList<Patch>) oInputStream.readObject();            



        // patches1 equals restored_patches1
    oInputStream.close();
} catch(Exception ex) {
    ex.printStackTrace();
}

注意i未考虑使用JSON,因为效率较低。

**注意:**我将考虑你的建议,即不将序列化对象存储为数据库中的字符串,而是将byte []替换为。