Added ability to use a custom mapper for serialization

json/src/main/java/tech/tablesaw/io/json/JsonWriteOptions.java

@@ -1,18 +1,23 @@
 package tech.tablesaw.io.json;
 
 import java.io.Writer;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
 import tech.tablesaw.io.Destination;
 import tech.tablesaw.io.WriteOptions;
 
 public class JsonWriteOptions extends WriteOptions {
 
   private final boolean asObjects;
   private final boolean header;
+  private final ObjectMapper mapper;
 
   private JsonWriteOptions(Builder builder) {
     super(builder);
     this.asObjects = builder.asObjects;
     this.header = builder.header;
+    this.mapper = builder.mapper;
   }
 
   public boolean asObjects() {
@@ -23,6 +28,8 @@ public boolean header() {
     return header;
   }
 
+  public ObjectMapper mapper() { return mapper; }
+
   public static Builder builder(Writer writer) {
     return new Builder(new Destination(writer));
   }
@@ -35,6 +42,7 @@ public static class Builder extends WriteOptions.Builder {
 
     private boolean asObjects = true;
     private boolean header = false;
+    private ObjectMapper mapper = new ObjectMapper().registerModule(new JavaTimeModule());
 
     protected Builder(Destination destination) {
       super(destination);
@@ -52,6 +60,11 @@ public JsonWriteOptions.Builder header(boolean header) {
       return this;
     }
 
+    public JsonWriteOptions.Builder mapper(ObjectMapper mapper) {
+      this.mapper = mapper;
+      return this;
+    }
+
     public JsonWriteOptions build() {
       return new JsonWriteOptions(this);
     }

json/src/main/java/tech/tablesaw/io/json/JsonWriter.java

@@ -30,8 +30,6 @@
 public class JsonWriter implements DataWriter<JsonWriteOptions> {
 
   private static final JsonWriter INSTANCE = new JsonWriter();
-  private static final ObjectMapper mapper =
-      new ObjectMapper().registerModule(new JavaTimeModule());
 
   static {
     register(Table.defaultWriterRegistry);
@@ -43,33 +41,33 @@ public static void register(WriterRegistry registry) {
   }
 
   public void write(Table table, JsonWriteOptions options) {
-    ArrayNode output = mapper.createArrayNode();
+    ArrayNode output = options.mapper().createArrayNode();
     if (options.asObjects()) {
       for (int r = 0; r < table.rowCount(); r++) {
-        ObjectNode row = mapper.createObjectNode();
+        ObjectNode row = options.mapper().createObjectNode();
         for (int c = 0; c < table.columnCount(); c++) {
-          row.set(table.column(c).name(), mapper.convertValue(table.get(r, c), JsonNode.class));
+          row.set(table.column(c).name(), options.mapper().convertValue(table.get(r, c), JsonNode.class));
         }
         output.add(row);
       }
     } else {
       if (options.header()) {
-        ArrayNode row = mapper.createArrayNode();
+        ArrayNode row = options.mapper().createArrayNode();
         for (int c = 0; c < table.columnCount(); c++) {
-          row.add(mapper.convertValue(table.column(c).name(), JsonNode.class));
+          row.add(options.mapper().convertValue(table.column(c).name(), JsonNode.class));
         }
         output.add(row);
       }
       for (int r = 0; r < table.rowCount(); r++) {
-        ArrayNode row = mapper.createArrayNode();
+        ArrayNode row = options.mapper().createArrayNode();
         for (int c = 0; c < table.columnCount(); c++) {
-          row.add(mapper.convertValue(table.get(r, c), JsonNode.class));
+          row.add(options.mapper().convertValue(table.get(r, c), JsonNode.class));
         }
         output.add(row);
       }
     }
     try (Writer writer = options.destination().createWriter()) {
-      String str = mapper.writeValueAsString(output);
+      String str = options.mapper().writeValueAsString(output);
       writer.write(str);
     } catch (IOException e) {
       throw new RuntimeIOException(e);

json/src/test/java/tech/tablesaw/io/json/JsonWriterTest.java

@@ -16,10 +16,20 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.StringWriter;
+import java.time.LocalDate;
+import java.time.format.DateTimeFormatter;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializerProvider;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+import com.fasterxml.jackson.databind.ser.std.StdSerializer;
 import org.junit.jupiter.api.Test;
 import tech.tablesaw.api.Table;
+import tech.tablesaw.io.Destination;
 
 public class JsonWriterTest {
 
@@ -54,4 +64,23 @@ public void arrayOfObjects() {
     String output = table.write().toString("json");
     assertEquals(json, output);
   }
+
+  @Test
+  public void withCustomMapper() {
+    var json = "[{\"a\":\"2021-01-01\"}, {\"a\":\"2021-02-01\"}]";
+    var table = Table.read().string(json, "json");
+    var mapper = new ObjectMapper();
+    mapper.registerModule(new SimpleModule().addSerializer(new StdSerializer<LocalDate>(LocalDate.class) {
+      final DateTimeFormatter FORMATTER = DateTimeFormatter.ofPattern("yyyy/MM/dd");
+      @Override
+      public void serialize(LocalDate localDate, JsonGenerator jsonGenerator, SerializerProvider serializerProvider)
+              throws IOException {
+        jsonGenerator.writeString(FORMATTER.format(localDate));
+      }
+    }));
+
+    var baos = new ByteArrayOutputStream();
+    new JsonWriter().write(table, new JsonWriteOptions.Builder(new Destination(baos)).mapper(mapper).build());
+    assertEquals(new String(baos.toByteArray()), "[{\"a\":\"2021/01/01\"},{\"a\":\"2021/02/01\"}]");
+  }
 }