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JBoss DMR

Posted by Kylin Soong on Apr 2, 2015 categorized as jboss

JBoss DMR

JBoss DMR(Dynamic Model Representation) is a siample management API of JBoss 7/WildFly. It’s key API is ModelNode which can be thought as a datastructure of all management activities. It has 2 main characteristics:

  • Dynamic Structure
  • JSON-like Format(can output JSON)

The following code snippet show how to form a ModelNode:

ModelNode node = new ModelNode();
node.get("description").set("A managable resource");
node.get("type").set(ModelType.OBJECT);
node.get("tail-comment-allowed").set(false);
node.get("attributes").get("foo").set("some description of foo");
node.get("attributes").get("bar").set("some description of bar");
node.get("attributes").get("list").add("value1");
node.get("attributes").get("list").add("value2");
node.get("attributes").get("list").add("value3");
node.get("value-type").get("size").set(ModelType.INT);
node.get("value-type").get("color").set(ModelType.STRING);
node.get("big-decimal-value").set(BigDecimal.valueOf(10.0));
node.get("big-integer-value").set(BigInteger.TEN);
node.get("bytes-value").set(new byte[] { (byte) 0, (byte) 55 });
node.get("double-value").set(Double.valueOf("55"));
node.get("max-double-value").set(Double.MAX_VALUE);
node.get("int-value").set(Integer.valueOf("12"));
node.get("max-int-value").set(Integer.MAX_VALUE);
node.get("long-value").set(Long.valueOf("14"));
node.get("max-long-value").set(Long.MAX_VALUE);
node.get("property-value").set("property", ModelType.PROPERTY);
node.get("expression-value").set(new ValueExpression("$expression"));
node.get("true-value").set(true);
node.get("false-value").set(false);
        
System.out.println(node);

Run the code will show it’s JSON-like Format:

{
    "description" => "A managable resource",
    "type" => OBJECT,
    "tail-comment-allowed" => false,
    "attributes" => {
        "foo" => "some description of foo",
        "bar" => "some description of bar",
        "list" => [
            "value1",
            "value2",
            "value3"
        ]
    },
    "value-type" => {
        "size" => INT,
        "color" => STRING
    },
    "big-decimal-value" => big decimal 10.0,
    "big-integer-value" => big integer 10,
    "bytes-value" => bytes {
        0x00, 0x37
    },
    "double-value" => 55.0,
    "max-double-value" => 1.7976931348623157E308,
    "int-value" => 12,
    "max-int-value" => 2147483647,
    "long-value" => 14L,
    "max-long-value" => 9223372036854775807L,
    "property-value" => ("property" => PROPERTY),
    "expression-value" => expression "$expression",
    "true-value" => true,
    "false-value" => false
}

In WildFly, all the management actions will be translated into the management commands that are encapsulated in the DMR format. For example, if we deploy cluster-demo1.war to WildFly, it will send the following JSON-like DMR commands to the deployment module:

[{
    "operation" =>"composite",
    "address" => [],
    "steps" => [
    {
	"operation" =>"add",
	"address" => [("deployment" =>"cluster-demo1.war")],
	"content" => [{
	    "path" =>"deployments/cluster-demo1.war",
	    "relative-to" =>"jboss.server.base.dir",
	}],
    },
    {
	"operation" =>"deploy",
	"address" => [("deployment" =>"cluster-demo1.war")]
    }
}]

Key Method of ModelNode

String toString() 
String toJSONString(false);
writeString(writer, false);
ModelNode formatAsJSON(writer, 0, true);
writeJSONString(writer, false);
ModelNode fromBase64(in);
long asLong()
long asLong(final long defVal)
int asInt()
int asInt(final int defVal)
boolean asBoolean()
boolean asBoolean(final boolean defVal)
String asString()
double asDouble()
double asDouble(final double defVal)
ModelType asType()
...

Examples

Form and Operate matrix Data

A matrix data, like a SQL Query, assuming a query have 2 columns and 2 rows.

final ModelNode outcome = new ModelNode();
outcome.get("outcome").set("success");
ModelNode resultsNode = new ModelNode();
ModelNode row1 = new ModelNode();
row1.get("column_1").set("value_11");
row1.get("column_2").set("value_12");
resultsNode.add(row1);
ModelNode row2 = new ModelNode();
row2.get("column_1").set("value_21");
row2.get("column_2").set("value_22");
resultsNode.add(row2);
outcome.get("result").set(resultsNode);
  
System.out.println(outcome);

List<ModelNode> list = outcome.get("result").asList();
System.out.println("column_1  column_2");
for(ModelNode rowNode : list) {
    System.out.println(rowNode.get("column_1").asString() + "  " + rowNode.get("column_2").asString());
}

Run above code the output like

{
    "outcome" => "success",
    "result" => [
        {
            "column_1" => "value_11",
            "column_2" => "value_12"
        },
        {
            "column_1" => "value_21",
            "column_2" => "value_22"
        }
    ]
}
column_1  column_2
value_11  value_12
value_21  value_22