public static ApplicationMetaData fromJsonString(String jsonString) {
        try {
            Slime data = SlimeUtils.jsonToSlime(jsonString);
            Inspector root = data.get();
            Inspector deploy = root.field("deploy");
            Inspector app = root.field("application");

            return new ApplicationMetaData(deploy.field("timestamp").asLong(),
                                           booleanField("internalRedeploy", false, deploy),
                                           ApplicationId.fromSerializedForm(app.field("id").asString()),
                                           app.field("checksum").asString(),
                                           app.field("generation").asLong(),
                                           app.field("previousActiveGeneration").asLong());
        } catch (Exception e) {
            throw new IllegalArgumentException("Error parsing json metadata", e);
        }
    }
Returns the previously active generation at the point when this application was created.
config-model-api/src/main/java/com/yahoo/config/application/api/ApplicationMetaData.java