How to retrieve and update records from a table through an OpenEdge REST Service using ProDataSets

How to retrieve and update records from a table through an OpenEdge REST Service using ProDataSets
What are the steps to update database records via an OpenEdge REST Service when using a ProDataSet
Example code using an OpenEdge REST web application with a ProDataSet json with before-image data.  

{
  "datasetName": {
    "prods:hasChanges" : true, // if no before-image data, property is absent
     "tableName1": [ // after table data
        {
        "prods:id" : "idValue", // unique id matching before and error rows
        "prods:rowState" :  "created | modified",
        "prods:hasErrors" : true,  //if no errors, property is absent
          ... //field values
          ... //nested records if dataset is NESTED
        },
        ...  //more tableName1 records
    ],
    "tableName2": [  //after table data
      {
        "prods:id" : "idValue", // unique id matching before and error rows
        "prods:rowState" :  "created | modified",
        "prods:hasErrors" : true,  //if no errors property absent
          ... //field values
          ... //nested records if dataset is NESTED
      },
        ...  //more tableName2 records
    ],
      ... //more tables/records
    
    "prods:before" : { // before table data
      "tableName1" : [    
        {
          "prods:id" : "idValue", // unique id matching after row
          "prods:rowState" :  "deleted | modified", 
          "prods:hasErrors" : true,  //only for deleted records
                                       if no errors property absent
          ... // field values
        },
        ... // more tableName1 records
      ],
    "tableName2" : [    
        {
          "prods:id" : "idValue",
          "prods:rowState" :  "deleted | modified",
          "prods:hasErrors" : true,  //only for deleted records
                                       if no errors property absent 
          ... // field values
        },
        ... // more tableName2 records
      ],
      ... //more before-tables/records
    },
    "prods:errors" : { // before table ERROR information
      "tableName1" : [ 
        {   
          "prods:id" : "idValue", // unique id matching after row  
          "prods:error" : "error-string"
        },
        ... //errors for more tableName1 records  
      ],
      ... //errors on more tables
    }
}

• The JSON object’s name is the ProDataSet name.
• The "prods:hasChanges" property indicates that the datasetName object contains before-image and possibly error information.
• The JSON arrays for each temp-table contain the ProDataSet after-table data.  
  • The JSON arrays are structured like what you would see with WRITE-JSON (with nested records, etc.), but each record object might contain the following additional properties (if the after-table record does not have a corresponding before-table record, these properties are absent).
    • "prods:id" – a string property uniquely identifying the record that is used to match up records in the prods:before and prods:errors sections.
    • "prods:rowState" – a string property indicating the row-state of the record. Valid values are "created" or "modified". Modified records have an entry in the prods:before section. Created records do not.
    • "prods:hasErrors" – a boolean property indicating whether the record’s before buffer’s ERROR attribute is true. When true, there is an entry in the prods:errors section containing the error-string value.
• The “prods:before” object contains the before-table records for the ProDataSet. If there are no before-tables in the ProDataSet, this object is not present in the JSON string. The before-table records are not nested, even if the dataset defines the after-tables in this way. Deleted records are in this section with no corresponding record in the after-table records. Created records do not have an entry in this section.
  • The prods:id property for each before-table row uniquely identifies the record. For modified records, the id matches the corresponding after-table record.
  • Valid values for prods:rowState are "deleted" and "modified".
  • The prods:hasErrors property is present in the before section for deleted records, where applicable.
• The "prods:error" object contains before-table error-string values for before-table records with ERROR=true.
  • The prods:id property matches that of the corresponding after-table record (modified and created records) or before-table record (deleted records) that has the prods:hasErrors property with a value of true.
  • The prods:error property contains the before-table record’s ERROR-STRING attribute.

1. If any before-image or error data is included in the JSON string, then the prods:hasChages property is required to be the first property in the JSON string, in order to set up the parsing of prods:before and prods:errors sections. This requirement also helps mitigate performance issues for parsing non-before-image JSON strings.
2. The prods:id property must be included in order to link records in the prods:before, prods:errors and after records sections.
3. Other than the information above explicit to before-image data, the following general rules apply:
   1. Temp-tables (whether in prods:before, prods:errors, or in the JSON after section) must be JSON Arrays consisting of JSON Objects representing the temp-table rows.
   2. Temp-table fields must conform to the data type mapping rules spelled out in the Working with JSON book.

• Create a new REST project or use an existing one within Developer Studio (PDSOE)
• Configure the AppServer used by the REST project to connect to the Sports2000 database.
• Add po_server_getdata.p and po_server_process_changes.p to the AppServer's PROPATH.
• Add po_server_getdata.p as a REST resource using the GET verb (e.g. /PurchaseOrders/{piPONum} ) and map the input and output parameters.
• Add po_server_process_changes.p as a REST resource using the PUT verb (e.g. /PurchaseOrdersChanges) and map the input-output parameter.
• Fetch one of the purchase orders by calling po_server_getdata.p from the REST client using an HTTP GET:

• ​Example: HTTP GET purchase orders

• Update the quantity (Qty) of the records containing LineNum 1, 2 and 4 with a PUT request:

PUT http://localhost:8980/RESTTestProjectService/rest/RESTTestProjectService/PurchaseOrdersChanges HTTP/1.1
User-Agent: Fiddler
Accept: application/json
Host: localhost:8980
Content-Length: 1521

{
    "request": {
        "dsPO": {
            "dsPO": {
                "prods:hasChanges": true,
                "ttPOLine": [{
                    "prods:id": "ttPOLine20736",
                    "prods:rowState": "modified",
                    "PONum": 8001,
                    "LineNum": 1,
                    "ItemNum": 3,
                    "Price": 16.55,
                    "Qty": 11,
                    "Discount": 0,
                    "ExtendedPrice": 49.65
                },
                {
                    "prods:id": "ttPOLine20737",
                    "prods:rowState": "modified",
                    "PONum": 8001,
                    "LineNum": 2,
                    "ItemNum": 45,
                    "Price": 81.0,
                    "Qty": 22,
                    "Discount": 0,
                    "ExtendedPrice": 405.0
                },
                {
                    "prods:id": "ttPOLine20738",
                    "prods:rowState": "modified",
                    "PONum": 8001,
                    "LineNum": 4,
                    "ItemNum": 47,
                    "Price": 11.77,
                    "Qty": 44,
                    "Discount": 0,
                    "ExtendedPrice": 58.85
                }],
                "prods:before": {
                    "ttPOLine": [{
                        "prods:id": "ttPOLine20736",
                        "prods:rowState": "modified",
                        "PONum": 8001,
                        "LineNum": 1,
                        "ItemNum": 3,
                        "Price": 16.55,
                        "Qty": 3,
                        "Discount": 0,
                        "ExtendedPrice": 49.65
                    },
                    {
                        "prods:id": "ttPOLine20737",
                        "prods:rowState": "modified",
                        "PONum": 8001,
                        "LineNum": 2,
                        "ItemNum": 45,
                        "Price": 81.0,
                        "Qty": 5,
                        "Discount": 0,
                        "ExtendedPrice": 405.0
                    },
                    {
                        "prods:id": "ttPOLine20738",
                        "prods:rowState": "modified",
                        "PONum": 8001,
                        "LineNum": 4,
                        "ItemNum": 47,
                        "Price": 11.77,
                        "Qty": 5,
                        "Discount": 0,
                        "ExtendedPrice": 58.85
                    }]
                }
            }
        }
    }
}