How to save a complex java object in a MySQL table

If you want to save complex java objects to MySQL you can serialize and save them as BLOB in a MySQL table.

For example you have an object “complexObject” from class “ComplexObject” and you want to save it in database.

The ComplexObject class must implements Serializable interface and you can serialize the objects like this:

ByteArrayOutputStream baos;

ObjectOutputStream out;

baos = new ByteArrayOutputStream();

try {

out = new ObjectOutputStream(baos);

out.writeObject(complexObject);

out.close();

} catch (IOException e) {

e.printStackTrace();

}

byte[] byteObject = baos.toByteArray();

to deserialize the object :

ByteArrayInputStream bais;

ObjectInputStream in;

try {

bais = new ByteArrayInputStream(byteObject);

in = new ObjectInputStream(bais);

complexObject = (ComplexObject) in.readObject();

in.close();

} catch (IOException ex) {

ex.printStackTrace();

} catch (ClassNotFoundException ex) {

ex.printStackTrace();

}

The MySQL table looks like this:

CREATE TABLE myTable(

…

complexObject BLOB,…

);

If you use Hibernate and Annotation you declare the complexObject transient, and a byte[] byteObject that will be persisted:

@Entity

@Table(name = “myTable”)

SomeClass{

private byte[] byteObject;

private ComplexObject complexObject;

…

@Transient

public ComplexObject getComplexObject() {

return complexObject;

}

public void setComplexObject(ComplexObject complexObject) {

this.complexObject = complexObject;

ByteArrayOutputStream baos;

ObjectOutputStream out;

baos = new ByteArrayOutputStream();

try {

out = new ObjectOutputStream(baos);

out.writeObject(complexObject);

out.close();

} catch (IOException e) {

e.printStackTrace();

}

this.byteObject = baos.toByteArray();

}

@Column(columnDefinition = “blob”)

public byte[] getByteObject() {

return byteObject;

}

public void setByteObject(byte[] byteObject) {

ByteArrayInputStream bais;

ObjectInputStream in;

try {

bais = new ByteArrayInputStream(byteObject);

in = new ObjectInputStream(bais);

complexObject = (ComplexObject) in.readObject();

in.close();

} catch (IOException ex) {

ex.printStackTrace();

} catch (ClassNotFoundException ex) {

ex.printStackTrace();

}

this.byteObject= byteObject;

}

}

Attention the table column must be BLOB, not varchar.

Because the ComplexObject is transient it will not be save in database, but the byteObject will be save.

-------------------------------------------------------------

毕业后头五年决定你的一生                                       10类最急需IT人才：Java开发者居首       

海量Android教程、开发资料和源码                         给将成为“Android高手”的10个建议 

成为Java高手的25个学习目标--非常经典               Android 4.1果冻豆新特性详解 

Java侵权诉讼Goog