Serialize Object To XML in java ignores some variable fields of my object

Question

I am trying to serialize my object to an xml file, the problem is that some of the instance variables of this object are not written in the xml file. I don't know why are they ignored and how to get the serialize method to write every variable in the xml file. I have noticed that when I set (using the setter) some of these variables are more likely to be written in xml file.

What I am asking:

1- I want to know why some of the instance variables are not written inside the XML file when their Object is serialized.

2- How to enforce all instance variables of my object to be written into the file, when I serialize that object to XML.

my class

package DBMS;

import JDBC.ResultSetMetaData;

public class Column {

private String colName= "";
private String type="";
private boolean isPrimary= false;
private boolean isAutoIncrement= false;
private int NullableState = ResultSetMetaData.columnNullableUnknown;
private boolean isReadOnly= false;
private boolean isSearchable= true;
private String tableName= "unknown";
private int incrementNextValue = 1;


public Column() {
    // TODO Auto-generated constructor stub

}

public Column(String n, String t) {

    colName = n;
    type=t;
}


public String getTableName() {
    return tableName;
}

public void setTableName(String s) {
    tableName = s;
}

public String getColName() {
    // TODO Auto-generated method stub
    return colName;
}

public void setColName(String s) {
    // TODO Auto-generated method stub
    colName = s;
}

public String getType() {
    return type;
}

public void setType(String type) {
    this.type = type;
}

public boolean isPrimary() {
    return isPrimary;
}

public void setPrimary(boolean isPrimary) {
    this.isPrimary = isPrimary;
}

public boolean isAutoIncrement() {
    return isAutoIncrement;
}

public void setAutoIncrement(boolean isAutoIncrement) {
    this.isAutoIncrement = isAutoIncrement;
}

public int getNullableState() {
    return NullableState;
}

public void setNullable(int Nullable) {
    this.NullableState = Nullable;
}

public boolean isReadOnly() {
    return isReadOnly;
}

public void setReadOnly(boolean isReadOnly) {
    this.isReadOnly = isReadOnly;
}

public boolean isSearchable() {
    return isSearchable;
}

public void setSearchable(boolean isSearchable) {
    this.isSearchable = isSearchable;
}

public int getIncrementNextValue() {
    return incrementNextValue;
}

public void setIncrementNextValue(int incrementNextValue) {
    this.incrementNextValue = incrementNextValue;
}

}

method serialize

public  void serializeObjectToXML(String xmlFileLocation, ArrayList<Column> objectToSerialize) throws Exception {

    FileOutputStream os = new FileOutputStream(xmlFileLocation);
    XMLEncoder encoder = new XMLEncoder(os);
    encoder.writeObject(objectToSerialize);
    encoder.close();
    os.close();
}

sample xml output

 <?xml version="1.0" encoding="UTF-8"?>
 -<java class="java.beans.XMLDecoder" version="1.7.0_07">
 -<object class="java.util.ArrayList">
 -<void method="add"> 
 -<object class="DBMS.Column">
 -<void property="autoIncrement"> <boolean>true</boolean> </void> 
 -<void property="colName"> <string>ID</string> </void> 
 -<void property="readOnly"> <boolean>true</boolean> </void> 
 -<void property="tableName"> <string>testSerialize</string> </void> 
 -<void property="type"> <string>int</string> </void> </object> </void>
 -<void method="add">
 -<object class="DBMS.Column">
 -<void property="colName"> <string>Name</string> </void> 
 -<void property="primary"> <boolean>true</boolean> </void>
 -<void property="tableName"> <string>testSerialize</string> </void>
 -<void property="type"> <string>string</string> </void> </object> </void> -<void    method="add"> 
 -<object class="DBMS.Column"> 
 -<void property="colName"> <string>info</string> </void>
 -<void property="tableName"> <string>testSerialize</string> </void> -<void property="type"> <string>string</string> </void> </object> </void> 
 -<void method="add">
 -<object class="DBMS.Column">
 -<void property="colName"> <string>data</string> </void>
 -<void property="tableName"> <string>testSerialize</string> </void>
 -<void property="type"> <string>string</string> </void> </object> </void> </object> </java>

Could you edit to make is clearer what you are asking? – tjons Dec 01 '13 at 00:01 — tjons, Dec 01 '13 at 00:01
Thanks Tjons for your concern, I have edited it. – Amr Saleh Dec 01 '13 at 00:11 — Amr Saleh, Dec 01 '13 at 00:11

score 4 · Accepted Answer · answered Dec 01 '13 at 00:52

4

Two things worth noting:

XMLEncoder does not look at private fields. It only looks at matching pairs of 'get' and 'set' methods (or 'is' and 'set' methods). You have a getNullableState method but the set-method does not match; you should rename setNullable to setNullableState.
XMLEncoder only writes values for properties which are different from their initial state. The initial state of each property is whatever value it has when the object is initially constructed.

So, one way to force a property value to be written is to make sure it has a value that's different from what it had when the object was constructed.

If you want to always write XML for every property, you may want to consider using JAXB instead of XMLEncoder.

answered Dec 01 '13 at 00:52

VGR

40,506
4
48
63

Thanks a lot VGR, your answer is clear and helpful :) and was just to the point. – Amr Saleh Dec 01 '13 at 01:54
and if I'm using XMLEncoder and want to ignore some fields, what I have to do ? transient doesn't work. – zond Feb 02 '16 at 14:25
@zond `transient` won't work, but [@Transient](http://docs.oracle.com/javase/8/docs/api/java/beans/Transient.html), placed on a get-method, will. – VGR Feb 02 '16 at 14:29
transient does not work properly with collections and arrays (( – zond Feb 03 '16 at 09:09
@zond You should ask a new question. Be sure to include enough code in your question for other people to reproduce your issue. – VGR Feb 03 '16 at 20:01
@VGR thanks, my problem was solved http://stackoverflow.com/questions/35173074/excluding-byte-from-serialization-of-xmlencoder – zond Feb 04 '16 at 07:20

score 2 · Answer 2 · answered Dec 01 '13 at 00:40

2

XMLEncoder uses the JavaBean pattern to serialize an object.

That means, it looks for a specific set of method names, not member variables, and calls those methods to transfer the resulting values to an XML document.

answered Dec 01 '13 at 00:40

Udo Klimaschewski

5,150
1
28
41

Thanks Udo for taking the time to edit my question and also answer it. :) – Amr Saleh Dec 01 '13 at 01:58

Serialize Object To XML in java ignores some variable fields of my object

2 Answers2