Allow configuring how string to number converters handle empty strings (#8506)

server/src/main/java/com/vaadin/data/converter/AbstractStringToNumberConverter.java

@@ -36,24 +36,32 @@ import com.vaadin.data.ValueContext;
  * @author Vaadin Ltd
  * @since 8.0
  */
-public abstract class AbstractStringToNumberConverter<T>
+public abstract class AbstractStringToNumberConverter<T extends Number>
         implements Converter<String, T> {
 
     private final String errorMessage;
+    private T emptyValue;
 
     /**
-     * Creates a new converter instance with the given error message.
+     * Creates a new converter instance with the given empty string value and
+     * error message.
      *
+     * @param emptyValue
+     *            the presentation value to return when converting an empty
+     *            string, may be <code>null</code>
      * @param errorMessage
      *            the error message to use if conversion fails
      */
-    protected AbstractStringToNumberConverter(String errorMessage) {
+    protected AbstractStringToNumberConverter(T emptyValue,
+            String errorMessage) {
+        this.emptyValue = emptyValue;
         this.errorMessage = errorMessage;
     }
 
     /**
-     * Returns the format used by {@link #convertToPresentation(Object, ValueContext)}
-     * and {@link #convertToModel(Object, ValueContext)}.
+     * Returns the format used by
+     * {@link #convertToPresentation(Object, ValueContext)} and
+     * {@link #convertToModel(Object, ValueContext)}.
      *
      * @param locale
      *            The locale to use
@@ -94,8 +102,8 @@ public abstract class AbstractStringToNumberConverter<T>
         }
 
         if (parsedValue == null) {
-            // Convert "" to null
-            return Result.ok(null);
+            // Convert "" to the empty value
+            return Result.ok(emptyValue);
         }
 
         return Result.ok(parsedValue);

server/src/main/java/com/vaadin/data/converter/StringToBigDecimalConverter.java

@@ -41,13 +41,29 @@ public class StringToBigDecimalConverter
         extends AbstractStringToNumberConverter<BigDecimal> {
 
     /**
-     * Creates a new converter instance with the given error message.
+     * Creates a new converter instance with the given error message. Empty
+     * strings are converted to <code>null</code>.
      *
      * @param errorMessage
      *            the error message to use if conversion fails
      */
     public StringToBigDecimalConverter(String errorMessage) {
-        super(errorMessage);
+        this(null, errorMessage);
+    }
+
+    /**
+     * Creates a new converter instance with the given empty string value and
+     * error message.
+     *
+     * @param emptyValue
+     *            the presentation value to return when converting an empty
+     *            string, may be <code>null</code>
+     * @param errorMessage
+     *            the error message to use if conversion fails
+     */
+    public StringToBigDecimalConverter(BigDecimal emptyValue,
+            String errorMessage) {
+        super(emptyValue, errorMessage);
     }
 
     @Override

server/src/main/java/com/vaadin/data/converter/StringToBigIntegerConverter.java

@@ -40,14 +40,31 @@ import com.vaadin.data.ValueContext;
  */
 public class StringToBigIntegerConverter
         extends AbstractStringToNumberConverter<BigInteger> {
+
     /**
-     * Creates a new converter instance with the given error message.
+     * Creates a new converter instance with the given error message. Empty
+     * strings are converted to <code>null</code>.
      *
      * @param errorMessage
      *            the error message to use if conversion fails
      */
     public StringToBigIntegerConverter(String errorMessage) {
-        super(errorMessage);
+        this(null, errorMessage);
+    }
+
+    /**
+     * Creates a new converter instance with the given empty string value and
+     * error message.
+     *
+     * @param emptyValue
+     *            the presentation value to return when converting an empty
+     *            string, may be <code>null</code>
+     * @param errorMessage
+     *            the error message to use if conversion fails
+     */
+    public StringToBigIntegerConverter(BigInteger emptyValue,
+            String errorMessage) {
+        super(emptyValue, errorMessage);
     }
 
     @Override
@@ -68,6 +85,10 @@ public class StringToBigIntegerConverter
                     if (number == null) {
                         return null;
                     } else {
+                        // Empty value will be a BigInteger
+                        if (number instanceof BigInteger) {
+                            return (BigInteger) number;
+                        }
                         return ((BigDecimal) number).toBigInteger();
                     }
                 });

server/src/main/java/com/vaadin/data/converter/StringToDoubleConverter.java

@@ -40,13 +40,28 @@ public class StringToDoubleConverter
         extends AbstractStringToNumberConverter<Double> {
 
     /**
-     * Creates a new converter instance with the given error message.
+     * Creates a new converter instance with the given error message. Empty
+     * strings are converted to <code>null</code>.
      *
      * @param errorMessage
      *            the error message to use if conversion fails
      */
     public StringToDoubleConverter(String errorMessage) {
-        super(errorMessage);
+        this(null, errorMessage);
+    }
+
+    /**
+     * Creates a new converter instance with the given empty string value and
+     * error message.
+     *
+     * @param emptyValue
+     *            the presentation value to return when converting an empty
+     *            string, may be <code>null</code>
+     * @param errorMessage
+     *            the error message to use if conversion fails
+     */
+    public StringToDoubleConverter(Double emptyValue, String errorMessage) {
+        super(emptyValue, errorMessage);
     }
 
     @Override

server/src/main/java/com/vaadin/data/converter/StringToFloatConverter.java

@@ -38,13 +38,28 @@ public class StringToFloatConverter
         extends AbstractStringToNumberConverter<Float> {
 
     /**
-     * Creates a new converter instance with the given error message.
+     * Creates a new converter instance with the given error message. Empty
+     * strings are converted to <code>null</code>.
      *
      * @param errorMessage
      *            the error message to use if conversion fails
      */
     public StringToFloatConverter(String errorMessage) {
-        super(errorMessage);
+        this(null, errorMessage);
+    }
+
+    /**
+     * Creates a new converter instance with the given empty string value and
+     * error message.
+     *
+     * @param emptyValue
+     *            the presentation value to return when converting an empty
+     *            string, may be <code>null</code>
+     * @param errorMessage
+     *            the error message to use if conversion fails
+     */
+    public StringToFloatConverter(Float emptyValue, String errorMessage) {
+        super(emptyValue, errorMessage);
     }
 
     @Override

server/src/main/java/com/vaadin/data/converter/StringToIntegerConverter.java

@@ -37,18 +37,33 @@ public class StringToIntegerConverter
         extends AbstractStringToNumberConverter<Integer> {
 
     /**
-     * Creates a new converter instance with the given error message.
+     * Creates a new converter instance with the given error message. Empty
+     * strings are converted to <code>null</code>.
      *
      * @param errorMessage
      *            the error message to use if conversion fails
      */
     public StringToIntegerConverter(String errorMessage) {
-        super(errorMessage);
+        this(null, errorMessage);
+    }
+
+    /**
+     * Creates a new converter instance with the given empty string value and
+     * error message.
+     *
+     * @param emptyValue
+     *            the presentation value to return when converting an empty
+     *            string, may be <code>null</code>
+     * @param errorMessage
+     *            the error message to use if conversion fails
+     */
+    public StringToIntegerConverter(Integer emptyValue, String errorMessage) {
+        super(emptyValue, errorMessage);
     }
 
     /**
      * Returns the format used by
-     * {@link #convertToPresentation(Object, ValueContext)}  and
+     * {@link #convertToPresentation(Object, ValueContext)} and
      * {@link #convertToModel(String, ValueContext)}.
      *
      * @param locale

server/src/main/java/com/vaadin/data/converter/StringToLongConverter.java

@@ -37,18 +37,34 @@ public class StringToLongConverter
         extends AbstractStringToNumberConverter<Long> {
 
     /**
-     * Creates a new converter instance with the given error message.
+     * Creates a new converter instance with the given error message. Empty
+     * strings are converted to <code>null</code>.
      *
      * @param errorMessage
      *            the error message to use if conversion fails
      */
     public StringToLongConverter(String errorMessage) {
-        super(errorMessage);
+        this(null, errorMessage);
     }
 
     /**
-     * Returns the format used by {@link #convertToPresentation(Object, ValueContext)}
-     * and {@link #convertToModel(String, ValueContext)}.
+     * Creates a new converter instance with the given empty string value and
+     * error message.
+     *
+     * @param emptyValue
+     *            the presentation value to return when converting an empty
+     *            string, may be <code>null</code>
+     * @param errorMessage
+     *            the error message to use if conversion fails
+     */
+    public StringToLongConverter(Long emptyValue, String errorMessage) {
+        super(emptyValue, errorMessage);
+    }
+
+    /**
+     * Returns the format used by
+     * {@link #convertToPresentation(Object, ValueContext)} and
+     * {@link #convertToModel(String, ValueContext)}.
      *
      * @param locale
      *            The locale to use

server/src/test/java/com/vaadin/tests/data/converter/AbstractConverterTest.java

@@ -17,22 +17,23 @@ public abstract class AbstractConverterTest {
 
     protected abstract Converter<?, ?> getConverter();
 
-    protected void assertValue(Object object, Result<?> result) {
-        assertValue(null, object, result);
+    protected <T> void assertValue(T expectedValue, Result<?> result) {
+        assertValue(null, expectedValue, result);
     }
 
-    protected void assertValue(String error, Object object, Result<?> result) {
+    protected <T> void assertValue(String assertMessage, T expectedValue,
+            Result<?> result) {
         Assert.assertNotNull("Result should never be null", result);
         Assert.assertFalse("Result is not ok", result.isError());
-        Assert.assertEquals(object,
+        Assert.assertEquals(expectedValue,
                 result.getOrThrow(message -> new AssertionError(
-                        error != null ? error : message)));
+                        assertMessage != null ? assertMessage : message)));
     }
 
-    protected void assertError(String expected, Result<?> result) {
+    protected void assertError(String expectedResultMessage, Result<?> result) {
         Assert.assertNotNull("Result should never be null", result);
         Assert.assertTrue("Result should be an error", result.isError());
-        Assert.assertEquals(expected, result.getMessage().get());
+        Assert.assertEquals(expectedResultMessage, result.getMessage().get());
     }
 
     protected String getErrorMessage() {

server/src/test/java/com/vaadin/tests/data/converter/StringToBigDecimalConverterTest.java

@@ -50,4 +50,15 @@ public class StringToBigDecimalConverterTest
                 new ValueContext(Locale.GERMAN));
         Assert.assertEquals(expected, converted);
     }
+
+    @Test
+    public void customEmptyValue() {
+        StringToBigDecimalConverter converter = new StringToBigDecimalConverter(
+                BigDecimal.ZERO, getErrorMessage());
+
+        assertValue(BigDecimal.ZERO,
+                converter.convertToModel("", new ValueContext()));
+        Assert.assertEquals("0", converter
+                .convertToPresentation(BigDecimal.ZERO, new ValueContext()));
+    }
 }

server/src/test/java/com/vaadin/tests/data/converter/StringToBigIntegerConverterTest.java

@@ -54,4 +54,16 @@ public class StringToBigIntegerConverterTest
                 "Value with specific locale was converted incorrectly",
                 expected, converted);
     }
+
+    @Test
+    public void customEmptyValue() {
+        StringToBigIntegerConverter converter = new StringToBigIntegerConverter(
+                BigInteger.ZERO, getErrorMessage());
+
+        assertValue(BigInteger.ZERO,
+                converter.convertToModel("", new ValueContext()));
+        Assert.assertEquals("0", converter
+                .convertToPresentation(BigInteger.ZERO, new ValueContext()));
+    }
+
 }

server/src/test/java/com/vaadin/tests/data/converter/StringToDoubleConverterTest.java

@@ -35,4 +35,14 @@ public class StringToDoubleConverterTest extends AbstractConverterTest {
         Assert.assertEquals("Failed", result.getMessage().get());
     }
 
+    @Test
+    public void customEmptyValue() {
+        StringToDoubleConverter converter = new StringToDoubleConverter(0.0,
+                getErrorMessage());
+
+        assertValue(0.0, converter.convertToModel("", new ValueContext()));
+        Assert.assertEquals("0",
+                converter.convertToPresentation(0.0, new ValueContext()));
+    }
+
 }

server/src/test/java/com/vaadin/tests/data/converter/StringToFloatConverterTest.java

@@ -1,5 +1,6 @@
 package com.vaadin.tests.data.converter;
 
+import org.junit.Assert;
 import org.junit.Test;
 
 import com.vaadin.data.ValueContext;
@@ -31,4 +32,15 @@ public class StringToFloatConverterTest extends AbstractStringConverterTest {
         assertValue(Float.valueOf(10),
                 getConverter().convertToModel("10", new ValueContext()));
     }
+
+    @Test
+    public void customEmptyValue() {
+        StringToFloatConverter converter = new StringToFloatConverter(
+                (float) 0.0, getErrorMessage());
+
+        assertValue((float) 0.0,
+                converter.convertToModel("", new ValueContext()));
+        Assert.assertEquals("0", converter.convertToPresentation((float) 0.0,
+                new ValueContext()));
+    }
 }

server/src/test/java/com/vaadin/tests/data/converter/StringToIntegerConverterTest.java

@@ -51,4 +51,14 @@ public class StringToIntegerConverterTest extends AbstractConverterTest {
         Assert.assertTrue(result.isError());
         Assert.assertEquals("Failed", result.getMessage().get());
     }
+
+    @Test
+    public void customEmptyValue() {
+        StringToIntegerConverter converter = new StringToIntegerConverter(0,
+                getErrorMessage());
+
+        assertValue(0, converter.convertToModel("", new ValueContext()));
+        Assert.assertEquals("0",
+                converter.convertToPresentation(0, new ValueContext()));
+    }
 }

server/src/test/java/com/vaadin/tests/data/converter/StringToLongConverterTest.java

@@ -1,5 +1,6 @@
 package com.vaadin.tests.data.converter;
 
+import org.junit.Assert;
 import org.junit.Test;
 
 import com.vaadin.data.Result;
@@ -48,4 +49,14 @@ public class StringToLongConverterTest extends AbstractStringConverterTest {
         assertValue(Long.MIN_VALUE, l);
 
     }
+
+    @Test
+    public void customEmptyValue() {
+        StringToLongConverter converter = new StringToLongConverter((long) 0,
+                getErrorMessage());
+
+        assertValue((long) 0, converter.convertToModel("", new ValueContext()));
+        Assert.assertEquals("0",
+                converter.convertToPresentation((long) 0, new ValueContext()));
+    }
 }