Update NumberSerTest.java (#4671)

Author: pjfanning

src/test/java/com/fasterxml/jackson/databind/ser/jdk/NumberSerTest.java

@@ -1,8 +1,14 @@
 package com.fasterxml.jackson.databind.ser.jdk;
 
+import java.io.IOException;
 import java.math.BigDecimal;
 import java.math.BigInteger;
+import java.text.DecimalFormat;
 
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.JsonSerializer;
+import com.fasterxml.jackson.databind.SerializerProvider;
+import com.fasterxml.jackson.databind.module.SimpleModule;
 import org.junit.jupiter.api.Test;
 
 import com.fasterxml.jackson.annotation.JsonFormat;
@@ -79,6 +85,36 @@ static class NumberWrapper {
         public NumberWrapper(Number v) { value = v; }
     }
 
+    static class BigDecimalHolder {
+        private final BigDecimal value;
+
+        public BigDecimalHolder(String num) {
+            value = new BigDecimal(num);
+        }
+
+        public BigDecimal getValue() {
+            return value;
+        }
+    }
+
+    static class BigDecimalAsStringSerializer extends JsonSerializer<BigDecimal> {
+        private final DecimalFormat df = new DecimalFormat("0.0");
+
+        @Override
+        public void serialize(BigDecimal value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
+            gen.writeString(df.format(value));
+        }
+    }
+
+    static class BigDecimalAsNumberSerializer extends JsonSerializer<BigDecimal> {
+        private final DecimalFormat df = new DecimalFormat("0.0");
+
+        @Override
+        public void serialize(BigDecimal value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
+            gen.writeNumber(df.format(value));
+        }
+    }
+
     /*
     /**********************************************************
     /* Test methods
@@ -167,4 +203,20 @@ public void testNumberType() throws Exception
         assertEquals(a2q("{'value':123}"), MAPPER.writeValueAsString(new NumberWrapper(BigInteger.valueOf(123))));
         assertEquals(a2q("{'value':0.025}"), MAPPER.writeValueAsString(new NumberWrapper(BigDecimal.valueOf(0.025))));
     }
+
+    @Test
+    public void testCustomSerializationBigDecimalAsString() throws Exception {
+        SimpleModule module = new SimpleModule();
+        module.addSerializer(BigDecimal.class, new BigDecimalAsStringSerializer());
+        ObjectMapper mapper = jsonMapperBuilder().addModule(module).build();
+        assertEquals(a2q("{'value':'2.0'}"), mapper.writeValueAsString(new BigDecimalHolder("2")));
+    }
+
+    @Test
+    public void testCustomSerializationBigDecimalAsNumber() throws Exception {
+        SimpleModule module = new SimpleModule();
+        module.addSerializer(BigDecimal.class, new BigDecimalAsNumberSerializer());
+        ObjectMapper mapper = jsonMapperBuilder().addModule(module).build();
+        assertEquals(a2q("{'value':2.0}"), mapper.writeValueAsString(new BigDecimalHolder("2")));
+    }
 }