Support for canonical JSON output in Jackson 2.16

src/test/java/com/fasterxml/jackson/databind/ser/CanonicalBigDecimalToString.java

@@ -0,0 +1,43 @@
+package com.fasterxml.jackson.databind.ser;
+
+import java.math.BigDecimal;
+
+public class CanonicalBigDecimalToString implements ValueToString<BigDecimal> {
+
+    public static final CanonicalBigDecimalToString INSTANCE = new CanonicalBigDecimalToString();
+
+    @Override
+    public String convert(BigDecimal value) {
+        BigDecimal stripped = value.stripTrailingZeros();
+        int scale = stripped.scale();
+        String text = stripped.toPlainString();
+        if (scale == 0) {
+            return text;
+        }
+
+        int pos = text.indexOf('.');
+        int exp;
+        if (pos >= 0) {
+            exp = pos - 1;
+
+            if (exp == 0) {
+                return text;
+            }
+
+            text = text.substring(0, pos) + text.substring(pos + 1);
+        } else {
+            exp = -scale;
+            int end = text.length();
+            while (end > 0 && text.charAt(end - 1) == '0') {
+                end --;
+            }
+            text = text.substring(0, end);
+        }
+
+        if (text.length() == 1) {
+            return text + 'E' + exp;
+        }
+
+        return text.substring(0, 1) + '.' + text.substring(1) + 'E' + exp;
+    }
+}

src/test/java/com/fasterxml/jackson/databind/ser/CanonicalBigDecimalToStringTest.java

@@ -0,0 +1,52 @@
+package com.fasterxml.jackson.databind.ser;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.math.BigDecimal;
+
+import org.junit.jupiter.api.Test;
+
+public class CanonicalBigDecimalToStringTest {
+
+    @Test
+    void testCanonicalDecimalHandling_1() throws Exception {
+        assertSerialized("1", new BigDecimal("1"));
+    }
+
+    @Test
+    void testCanonicalDecimalHandling_1_000() throws Exception {
+        assertSerialized("1", new BigDecimal("1.000"));
+    }
+
+    @Test
+    void testCanonicalDecimalHandling_10_1000() throws Exception {
+        assertSerialized("1.01E1", new BigDecimal("10.1000"));
+    }
+
+    @Test
+    void testCanonicalDecimalHandling_1000() throws Exception {
+        assertSerialized("1E3", new BigDecimal("1000"));
+    }
+
+    @Test
+    void testCanonicalDecimalHandling_0_00000000010() throws Exception {
+        assertSerialized("0.0000000001", new BigDecimal("0.00000000010"));
+    }
+
+    @Test
+    void testCanonicalDecimalHandling_1000_00010() throws Exception {
+        assertSerialized("1.0000001E3", new BigDecimal("1000.00010"));
+    }
+
+    @Test
+    void testCanonicalHugeDecimalHandling() throws Exception {
+        BigDecimal actual = new BigDecimal("123456789123456789123456789123456789.123456789123456789123456789123456789123456789000");
+        assertSerialized("1.23456789123456789123456789123456789123456789123456789123456789123456789123456789E35", actual);
+    }
+
+    private void assertSerialized(String expected, BigDecimal actual) {
+        CanonicalBigDecimalToString serializer = new CanonicalBigDecimalToString();
+        assertEquals(expected, serializer.convert(actual));
+    }
+
+}

src/test/java/com/fasterxml/jackson/databind/ser/CanonicalJsonGeneratorDecorator.java

@@ -0,0 +1,21 @@
+package com.fasterxml.jackson.databind.ser;
+
+import java.math.BigDecimal;
+
+import com.fasterxml.jackson.core.JsonFactory;
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.core.JsonGeneratorDecorator;
+
+public class CanonicalJsonGeneratorDecorator implements JsonGeneratorDecorator {
+
+    private ValueToString<BigDecimal> _serializer;
+
+    public CanonicalJsonGeneratorDecorator(ValueToString<BigDecimal> serializer) {
+        this._serializer = serializer;
+    }
+
+    @Override
+    public JsonGenerator decorate(JsonFactory factory, JsonGenerator generator) {
+        return new CanonicalNumberGenerator(generator, _serializer);
+    }
+}

src/test/java/com/fasterxml/jackson/databind/ser/CanonicalJsonMapper.java

@@ -0,0 +1,65 @@
+package com.fasterxml.jackson.databind.ser;
+
+import java.math.BigDecimal;
+
+import com.fasterxml.jackson.core.JsonFactory;
+import com.fasterxml.jackson.core.JsonGeneratorDecorator;
+import com.fasterxml.jackson.core.PrettyPrinter;
+import com.fasterxml.jackson.core.StreamWriteFeature;
+import com.fasterxml.jackson.core.util.DefaultIndenter;
+import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;
+import com.fasterxml.jackson.core.util.Separators;
+import com.fasterxml.jackson.core.util.Separators.Spacing;
+import com.fasterxml.jackson.databind.MapperFeature;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.databind.cfg.JsonNodeFeature;
+import com.fasterxml.jackson.databind.json.JsonMapper;
+
+public class CanonicalJsonMapper {
+    public static final DefaultIndenter CANONICAL_INDENTEER = new DefaultIndenter("    ", "\n");
+
+    public static final PrettyPrinter CANONICAL_PRETTY_PRINTER = new DefaultPrettyPrinter()
+        .withObjectIndenter(CANONICAL_INDENTEER)
+        .withSeparators(Separators.createDefaultInstance().withObjectFieldValueSpacing(Spacing.AFTER));    
+
+    public static class Builder {
+        private ValueToString<BigDecimal> _numberToString = CanonicalBigDecimalToString.INSTANCE;
+        private boolean _enablePrettyPrinting = false;
+
+        private Builder() {
+            // Don't allow to create except via builder method
+        }
+
+        public Builder prettyPrint() {
+            _enablePrettyPrinting = true;
+            _numberToString = PrettyBigDecimalToString.INSTANCE;
+            return this;
+        }
+
+        public JsonMapper build() {
+            JsonGeneratorDecorator decorator = new CanonicalJsonGeneratorDecorator(_numberToString);
+
+            JsonFactory factory = JsonFactory.builder() //
+                .decorateWith(decorator)
+                .build();
+            JsonMapper.Builder builder = JsonMapper.builder(factory) //
+                .enable(SerializationFeature.ORDER_MAP_ENTRIES_BY_KEYS) //
+                .enable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY) //
+                .enable(JsonNodeFeature.WRITE_PROPERTIES_SORTED); //
+
+            if (_enablePrettyPrinting) {
+                builder = builder //
+                    .enable(SerializationFeature.INDENT_OUTPUT) //
+                    .enable(StreamWriteFeature.WRITE_BIGDECIMAL_AS_PLAIN) //
+                    .defaultPrettyPrinter(CANONICAL_PRETTY_PRINTER) //
+                ;
+            }
+
+            return builder.build();
+        }
+    }
+
+    public static CanonicalJsonMapper.Builder builder() {
+        return new Builder();
+    }
+}