Updating values in a yaml file using snakeYaml

Question

Is there any way to edit/delete the values in a YAMLfile using java.

I'm using struts2-jquery-grid where the data will be populated from YAML file. Now, If I edit the field(s), it should be saved in YAML file. I am able to read the value from and write the values to a file in YAML format using yaml.load() and yaml.dump() respectively. But, I don't have any idea to do edit and delete the specific field.

I've gone through http://code.google.com/p/snakeyaml/wiki/Documentation#Dumping_YAML link where I read that we can use template processor and other options like defining order of java bean property, comments to make ease of yaml . But all those doesn't make any sense to me.

Here is my code to serialize the list of object called assumption here. In gridModel.add(assumption); , I'm storing the values of class Assumption(bean class with fetters and setters) to the list here in gridModel .

       gridModel.add(assumption);

       try {

        FileWriter pr=new FileWriter("D:/yaml.yaml");

        DumperOptions options = new DumperOptions();

         options.setDefaultFlowStyle(DumperOptions.FlowStyle.BLOCK);

        Yaml yaml = new Yaml(options);
        String output=yaml.dump(gridModel);//,Tag.MAP, null);
        pr.write(output);
        System.out.print(pr.toString());
        System.out.println();

        pr.close();
        }catch(Exception e){
            e.printStackTrace();
        }

The outout I'm getting in a file called yaml.yaml as:

• !!com.example.Assumption column1: '1' column2: Balwant column3: SPJ column4: rerer column5: null
• !!com.example.Assumption column1: '' column2: Vikas column3: RNC column4: erer column5: null
• !!com.example.Assumption column1: '3' column2: '' column3: PNBE column4: erer column5: null
• !!com.example.Assumption column1: '4' column2: Diwakar column3: BGP column4: rerer column5: null
• !!com.example.Assumption column1: '5' column2: Ajay column3: Godda column4: '' column5: null

For De-serialization the code is:

            InputStream input = new FileInputStream(new File("D:/yaml.yaml"));
    Yaml yaml = new Yaml();
    for (Object data : yaml.loadAll(input))
        System.out.println("Data:"+data);

The output to the console is :

Data:[Assumption [column1=1, column2=Balwant, column3=SPJ, column4=rerer, column5=null], Assumption [column1=, column2=Vikas, column3=RNC, column4=erer, column5=null], Assumption [column1=3, column2=, column3=PNBE, column4=erer, column5=null], Assumption [column1=4, column2=Diwakar, column3=BGP, column4=rerer, column5=null], Assumption [column1=5, column2=Ajay, column3=Godda, column4=, column5=null]]

I'm new to yaml and struts2. So, please answer a clean solution. Correct me, if I'm wrong while describing the requirement. Thanks in advance...

Answer 1

The only way I think to edit is to overwrite the existing yaml. We need to get the values from grid and overwrite ti to the existing one.