Recommended approach for avoiding a duplicate in server

[edulid]

I have a simple table with its datasource, say having fields id, field1, field2, and field3.

I got an insert request from the client. I want that no duplicates are inserted to the table regarding field1 and field2 only (so id and field3 are ignored).

What approach would you recommend ?

I got three ideas:
1) Intercept the insert dsRequest in a DMI method, check for duplicates, and return an error status if the row already exists.
2) Have a server-side validation in the datasource.ds.xml. Is this type of validation possible/feasible in this scenario?
3) Have the DB guard or something similar, i.e. validation to the DB- level.

I tend to prefer 1), since it is simple. But I would also like 2) if it is possible to do. If yes, what type of validation should the field/s have?

Using Smartgwt 4.1 p.

[Isomorphic]

For #2, add a validator of type "serverCustom". These can be done as Velocity expressions, Server Script or DMI. Doing it as DMI would be essentially very similar to #1.

You can *also* do #3 just as a failsafe, but you would still need either #1 or #2 in order to provide end users with a reasonable error message.

[Blama]

2) Have a server-side validation in the datasource.ds.xml. Is this type of validation possible/feasible in this scenario?

I have SmartGWT 4.1p code for this (don't know the exact status), let me check on Monday.

Best regards,
Blama

[Blama]

Hi edulid,

I have this code. I used it once for "giving meaningful error messages to the user" for Unique Constraint violations.
I don't know the state of it as I never used it in production. It would be great if you could post your final code here if this is useful to you:

ValidatorUniqueManyColumns.java:

import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import com.isomorphic.criteria.AdvancedCriteria;
import com.isomorphic.criteria.Criterion;
import com.isomorphic.criteria.DefaultOperators;
import com.isomorphic.criteria.criterion.SimpleCriterion;
import com.isomorphic.datasource.DSRequest;
import com.isomorphic.datasource.DSResponse;
import com.isomorphic.datasource.DataSource;
import com.isomorphic.datasource.Validator;
import com.isomorphic.log.Logger;

public class ValidatorUniqueManyColumns {
	Logger log = new Logger("com.isomorphic." + ValidatorUniqueManyColumns.class.getName());

	public boolean condition(Object value, Validator validator, String fieldName, Map<String, Object> record, DataSource ds) throws Exception {

		// We have additional values we need to check. These can - but most likely
		// are not - in "values".
		// Therefore we need to get them from the DB with the current PK.
		@SuppressWarnings("unchecked")
		Map<String, Object> dbValues = ds.fetchById(record.get(ds.getPrimaryKey()));

		// The Multiple Unique Validator can validate uniqueness for one or many
		// additional Columns.
		// If it is one column, the type is String, otherwise it's List. We unify.
		List<String> fieldsToCheck = new ArrayList<String>();

		// The field we call the validator for
		fieldsToCheck.add(fieldName);

		if (validator.getObjectProperty("additionalUniqueField") instanceof String)
			fieldsToCheck.add(validator.getProperty("additionalUniqueField"));
		else if (validator.getObjectProperty("additionalUniqueField") instanceof List) {
			@SuppressWarnings("unchecked")
			Iterator<String> itr = validator.getListProperty("additionalUniqueField").listIterator();
			while (itr.hasNext()) {
				String additionalColumn = itr.next();
				fieldsToCheck.add(additionalColumn);
			}
		}
		// Now we have the fieldname to validate as well as all other fieldnames

		// We build a list of Criterion that we'll feed to AdvancedCriteria later
		// on. The values are taken either from record or from the DB.
		ArrayList<Criterion> a = new ArrayList<Criterion>();

		Iterator<String> itr = fieldsToCheck.listIterator();
		while (itr.hasNext()) {
			String columnToCheck = itr.next();
			if (record.containsKey(columnToCheck))
				// Taken from sent record
				a.add(new SimpleCriterion(columnToCheck, DefaultOperators.Equals, record.get(columnToCheck)));
			else
				// Taken from DB
				a.add(new SimpleCriterion(columnToCheck, DefaultOperators.Equals, dbValues.get(columnToCheck)));
		}

		Criterion[] myArray = new Criterion[a.size()];
		final AdvancedCriteria ac = new AdvancedCriteria(DefaultOperators.And, a.toArray(myArray));
		DSRequest r = new DSRequest(ds.getName(), DataSource.OP_FETCH) {
			{
				setAdvancedCriteria(ac);
			}
		};
		DSResponse resp = r.execute();

		// Now we got the element count with the values.
		// Now two possibilities:
		// Add -> We want a 0-count.
		// Update -> We want either a 0-count or the same PK as before
		if (resp.getTotalRows() == 0)
			return true;
		else if (resp.getTotalRows() >= 2)
			return false;
		else {
			// Check for changed PK:
			// If no old PK (=Add) and we find a row nevertheless, the Add would fail.
			// The good case is handled above (at "resp.getTotalRows() == 0")
			if (record.get(ds.getPrimaryKey()) == null)
				return false;
			// Compare old and new value (in case of an update)
			BigDecimal oldvalue = BigDecimal.valueOf((Long) record.get(ds.getPrimaryKey()));
			@SuppressWarnings("rawtypes")
			BigDecimal newvalue = (BigDecimal) ((Map) resp.getRecords().get(0)).get(ds.getPrimaryKey());
			boolean isSameRow = oldvalue.compareTo(newvalue) == 0;
			return isSameRow;
		}
	}
};

.ds.xml usage:

<field name="POSITION" type="integer" required="true" editorType="SpinnerItem">
	<validators>
		<validator type="serverCustom">
			<serverObject lookupStyle="new" className="com.mycompany.myproj.server.worker.validator.ValidatorUniqueManyColumns" />
			<additionalUniqueField>TYPE</additionalUniqueField>
			<errorMessage>Jede Position darf nur einmal vorkommen!</errorMessage>
		</validator>
		<validator type="integerRange" min="1" max="100" errorMessage="Bitte Sie eine Position zwischen 1 und 100 aus!" />
	</validators>
</field>

Best regards,
Blama

[edulid]

Hi Blama,

thanks for the code, I will take a look.

[edulid]

Hi Blama, thanks for the code, I used it this way:

public boolean condition(Object value, Validator validator,
			String fieldName, Map<String, Object> record, DataSource ds,
			RPCManager rpcManager) throws Exception {

		Map<String, Object> dbValues = new HashMap<String, Object>();

		if (record.get(ds.getPrimaryKey()) != null) {
			dbValues = ds.fetchById(record.get(ds.getPrimaryKey()));
		}

		List<String> fieldsToCheck = new ArrayList<String>();

		fieldsToCheck.add(fieldName);

		if (validator.getObjectProperty("additionalUniqueField") instanceof String)
			fieldsToCheck.add(validator.getProperty("additionalUniqueField"));
		else if (validator.getObjectProperty("additionalUniqueField") instanceof List) {
			Iterator<String> itr = validator.getListProperty(
					"additionalUniqueField").listIterator();
			while (itr.hasNext()) {
				String additionalColumn = itr.next();
				fieldsToCheck.add(additionalColumn);
			}
		}

		List<Criterion> criterions = new ArrayList<Criterion>();

		Iterator<String> itr = fieldsToCheck.listIterator();
		while (itr.hasNext()) {
			String columnToCheck = itr.next();
			if (record.containsKey(columnToCheck))
				criterions.add(new SimpleCriterion(columnToCheck,
						DefaultOperators.Equals, record.get(columnToCheck)));
			else
				criterions.add(new SimpleCriterion(columnToCheck,
						DefaultOperators.Equals, dbValues.get(columnToCheck)));
		}

		final AdvancedCriteria ac = new AdvancedCriteria(DefaultOperators.And,
				criterions.toArray(new Criterion[] {}));
		DSRequest request = new DSRequest(ds.getName(), DataSource.OP_FETCH,
				rpcManager);
		request.setAdvancedCriteria(ac);

		DSResponse response = request.execute();

		/*
		 * Now we got the element count with the values. Now two possibilities:
		 * Add -> We want a 0-count. Update -> We want either a 0-count or the
		 * same PK as before.
		 */
		if (response.getTotalRows() == 0) {
			return true;
		} else if (response.getTotalRows() >= 2) {
			return false;
		} else {
			/*
			 * Check for changed PK: If no old PK (=Add) and we find a row
			 * nevertheless, the Add would fail. The good case is handled above
			 * (at "resp.getTotalRows() == 0").
			 */
			if (record.get(ds.getPrimaryKey()) == null) {
				return false;
			}
			/* Compare old and new value (in case of an update). */
			BigDecimal oldvalue = BigDecimal.valueOf((Long) record.get(ds
					.getPrimaryKey()));
			BigDecimal newvalue = (BigDecimal) response.getDataMap().get(
					ds.getPrimaryKey());
			boolean isSameRow = oldvalue.compareTo(newvalue) == 0;
			return isSameRow;
		}
	}

[mahbal]

Hi

When i tried to implement this code in my project there is no error in respective java file but while running code server i got the following error

[ERROR] Line 242: No source code is available for type com.isomorphic.datasource.DataSource; did you forget to inherit a required module?
[INFO] [ERROR] Line 246: No source code is available for type com.isomorphic.datasource.Validator; did you forget to inherit a required module?
[INFO] [ERROR] Line 263: No source code is available for type com.isomorphic.criteria.Criterion; did you forget to inherit a required module?
[INFO] [ERROR] Line 270: No source code is available for type com.isomorphic.criteria.criterion.SimpleCriterion; did you forget to inherit a required module?
[INFO] [ERROR] Line 270: No source code is available for type com.isomorphic.criteria.DefaultOperators; did you forget to inherit a required module?
[INFO] [ERROR] Line 277: No source code is available for type com.isomorphic.criteria.AdvancedCriteria; did you forget to inherit a required module?
[INFO] [ERROR] Line 278: No source code is available for type com.isomorphic.datasource.DSRequest; did you forget to inherit a required module?
[INFO] [ERROR] Line 283: No source code is available for type com.isomorphic.datasource.DSResponse; did you forget to inherit a required module?


Note: isomorphic-core-rpc-5.0.jar is already available in maven dependency

[Isomorphic]

These errors are not coming from SmatGWT. They are warnings from your IDE indicating that source code is not available for server-side classes, which is actually a normal and expected condition despite your IDE reporting it as an "error".

[mahbal]

But due to this warnings the code server is not getting started so what can i do to over come this issue

[Isomorphic]

This warning would not prevent the code server from starting. Look at the complete log to find the actual problem.

Just in case: SmartGWT comes with classes that are for use on the server-side (com.isomorphic.*) and classes that are meant for use on the client side (com.smartgwt.*). Make sure you have read the QuickStart Guide in its entirety so you understand the distinction.

[mahbal]

Link succeeded
[INFO] Compilation succeeded -- 17.502s
[INFO] Compile completed in 17865 ms
[INFO] binding: user.agent=safari
[INFO] binding: compiler.useSourceMaps=true
[INFO] binding: locale=en
[INFO] Compiling module com.myproject.myapp.Application
[INFO] Validating units:
[INFO] Ignored 2 units with compilation errors in first pass.
[INFO] Compile with -strict or with -logLevel set to TRACE or DEBUG to see all errors.
[INFO] [ERROR] Errors in 'file:/O:/eclipse/Workspace/myapp/src/main/java/com/myproject/myapp/client/pages/lab/mahesh/MaheshLab.java'
[INFO] [ERROR] Line 252: No source code is available for type com.isomorphic.datasource.DataSource; did you forget to inherit a required module?
[INFO] [ERROR] Line 256: No source code is available for type com.isomorphic.datasource.Validator; did you forget to inherit a required module?
[INFO] [ERROR] Line 273: No source code is available for type com.isomorphic.criteria.Criterion; did you forget to inherit a required module?
[INFO] [ERROR] Line 280: No source code is available for type com.isomorphic.criteria.criterion.SimpleCriterion; did you forget to inherit a required module?
[INFO] [ERROR] Line 280: No source code is available for type com.isomorphic.criteria.DefaultOperators; did you forget to inherit a required module?
[INFO] [ERROR] Line 287: No source code is available for type com.isomorphic.criteria.AdvancedCriteria; did you forget to inherit a required module?
[INFO] [ERROR] Line 288: No source code is available for type com.isomorphic.datasource.DSRequest; did you forget to inherit a required module?
[INFO] [ERROR] Line 293: No source code is available for type com.isomorphic.datasource.DSResponse; did you forget to inherit a required module?
[INFO] [ERROR] Compiler returned false
[ERROR] com.google.gwt.core.ext.UnableToCompleteException: (see previous log entries)
[ERROR] at com.google.gwt.dev.codeserver.Recompiler.compile(Recompiler.java:128)
[ERROR] at com.google.gwt.dev.codeserver.ModuleState.<init>(ModuleState.java:58)
[ERROR] at com.google.gwt.dev.codeserver.CodeServer.makeModules(CodeServer.java:120)
[ERROR] at com.google.gwt.dev.codeserver.CodeServer.start(CodeServer.java:95)
[ERROR] at com.google.gwt.dev.codeserver.CodeServer.main(CodeServer.java:71)
[ERROR] at com.google.gwt.dev.codeserver.CodeServer.main(CodeServer.java:49)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 23.283 s
[INFO] Finished at: 2014-12-16T17:24:01+05:30
[INFO] Final Memory: 25M/59M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:gwt-maven-plugin:2.6.1:run-codeserver (default-cli) on project myapp: Command [[
[ERROR] C:\Program Files (x86)\Java\jdk1.7.0_72\jre\bin\java -Xmx512m -classpath O:\Eclipse\Workspace\myapp\target\classes;
O:\Eclipse\Workspace\myapp\src\main\java;O:\Maven\Repository\com\google\gwt\gwt-user\2.6.1\gwt-user-2.6.1.jar;O:\Maven\Reposit......

[ERROR] ]] failed with status 1
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoExecutionException

[Blama]

myproject/myapp/client

[mahbal]

So i should replace com.isomorphic with com.smartgwt to over come this issue is it

[Blama]

Hi mahbal,

no, you should use the code on the server and the server only (as isomorphic wrote: com.isomorphic.* is server only, com.smartgwt.* is client only). Do you use SmartGWT Pro/Power/EE-Eval/EE (I think so)?

Copy the java code into a validator folder under "server" and use like in the ".ds.xml usage" in the post.

Please also read the Quick Start Guide regarding SmartGWT Server Framework.

Best regards,
Blama

[mahbal]

Hi Blama/Isomorphic
First of all thanks for your help & support .
1)Since iam new to smartgwt iam not sure of how to call this function from my client side java file . If its possible can you show me how can i call this function from client side and how the "com.isomorphic" parameters for Validator ,DataSource can be declared in client side and how can i pass this to the function.


public boolean condition(Object value, Validator validator, String fieldName, Map<String, Object> record, DataSource ds)

2)Whether this function checks only when we do insert operation or whether i can use it to check manually whether validator is working or not before performing insert operation .

3)Can you post the full ds.xml file.



Thank's