feat: Support getOrNull and getOrDefault in Struct (#3914)

* feat: Support getOrNull and getOrDefault in Struct

* Addressed comments

* Change Function interface to BiFunction

* Update clirr ignored differences

Author: sakthivelmanii

google-cloud-spanner/clirr-ignored-differences.xml

@@ -1008,4 +1008,24 @@
     <className>com/google/cloud/spanner/TransactionManager</className>
     <method>com.google.cloud.spanner.TransactionContext begin(com.google.cloud.spanner.AbortedException)</method>
   </difference>
+  <difference>
+    <differenceType>7012</differenceType>
+    <className>com/google/cloud/spanner/StructReader</className>
+    <method>java.lang.Object getOrNull(int, java.util.function.BiFunction)</method>
+  </difference>
+  <difference>
+    <differenceType>7012</differenceType>
+    <className>com/google/cloud/spanner/StructReader</className>
+    <method>java.lang.Object getOrNull(java.lang.String, java.util.function.BiFunction)</method>
+  </difference>
+  <difference>
+    <differenceType>7012</differenceType>
+    <className>com/google/cloud/spanner/StructReader</className>
+    <method>java.lang.Object getOrDefault(int, java.util.function.BiFunction, java.lang.Object)</method>
+  </difference>
+  <difference>
+    <differenceType>7012</differenceType>
+    <className>com/google/cloud/spanner/StructReader</className>
+    <method>java.lang.Object getOrDefault(java.lang.String, java.util.function.BiFunction, java.lang.Object)</method>
+  </difference>
 </differences>

google-cloud-spanner/src/main/java/com/google/cloud/spanner/StructReader.java

@@ -24,6 +24,7 @@
 import java.math.BigDecimal;
 import java.util.List;
 import java.util.UUID;
+import java.util.function.BiFunction;
 import java.util.function.Function;
 
 /**
@@ -176,6 +177,60 @@ default float getFloat(String columnName) {
    */
   String getString(String columnName);
 
+  /**
+   * @param columnIndex index of the column
+   * @return the value of a column with type T or null if the column contains a null value
+   *     <p>Example
+   *     <pre>{@code
+   * Struct row = ...
+   * String name = row.getOrNull(1, StructReader::getString)
+   * }</pre>
+   */
+  default <T> T getOrNull(int columnIndex, BiFunction<StructReader, Integer, T> function) {
+    return isNull(columnIndex) ? null : function.apply(this, columnIndex);
+  }
+
+  /**
+   * @param columnName index of the column
+   * @return the value of a column with type T or null if the column contains a null value
+   *     <p>Example
+   *     <pre>{@code
+   * Struct row = ...
+   * String name = row.getOrNull("name", StructReader::getString)
+   * }</pre>
+   */
+  default <T> T getOrNull(String columnName, BiFunction<StructReader, String, T> function) {
+    return isNull(columnName) ? null : function.apply(this, columnName);
+  }
+
+  /**
+   * @param columnIndex index of the column
+   * @return the value of a column with type T, or the given default if the column value is null
+   *     <p>Example
+   *     <pre>{@code
+   * Struct row = ...
+   * String name = row.getOrDefault(1, StructReader::getString, "")
+   * }</pre>
+   */
+  default <T> T getOrDefault(
+      int columnIndex, BiFunction<StructReader, Integer, T> function, T defaultValue) {
+    return isNull(columnIndex) ? defaultValue : function.apply(this, columnIndex);
+  }
+
+  /**
+   * @param columnName name of the column
+   * @return the value of a column with type T, or the given default if the column value is null
+   *     <p>Example
+   *     <pre>{@code
+   * Struct row = ...
+   * String name = row.getOrDefault("name", StructReader::getString, "")
+   * }</pre>
+   */
+  default <T> T getOrDefault(
+      String columnName, BiFunction<StructReader, String, T> function, T defaultValue) {
+    return isNull(columnName) ? defaultValue : function.apply(this, columnName);
+  }
+
   /**
    * @param columnIndex index of the column
    * @return the value of a non-{@code NULL} column with type {@link Type#json()}.

google-cloud-spanner/src/test/java/com/google/cloud/spanner/StructTest.java

@@ -57,6 +57,48 @@ public void builder() {
     assertThat(struct.getLong(1)).isEqualTo(2);
   }
 
+  @Test
+  public void getOrNullTests() {
+    Struct struct =
+        Struct.newBuilder()
+            .set("f1")
+            .to("x")
+            .set("f2")
+            .to(2)
+            .set("f3")
+            .to(Value.bool(null))
+            .build();
+    String column1 = struct.getOrNull(0, StructReader::getString);
+    assertThat(column1).isEqualTo("x");
+
+    Long column2 = struct.getOrNull(1, StructReader::getLong);
+    assertThat(column2).isEqualTo(2);
+
+    String column3 = struct.getOrNull("f3", StructReader::getString);
+    assertThat(column3).isNull();
+  }
+
+  @Test
+  public void getOrDefaultTests() {
+    Struct struct =
+        Struct.newBuilder()
+            .set("f1")
+            .to("x")
+            .set("f2")
+            .to(2)
+            .set("f3")
+            .to(Value.bool(null))
+            .build();
+    String column1 = struct.getOrDefault(0, StructReader::getString, "");
+    assertThat(column1).isEqualTo("x");
+
+    Long column2 = struct.getOrDefault("f2", StructReader::getLong, -1L);
+    assertThat(column2).isEqualTo(2);
+
+    String column3 = struct.getOrDefault(2, StructReader::getString, "");
+    assertThat(column3).isEqualTo("");
+  }
+
   @Test
   public void duplicateFields() {
     // Duplicate fields are allowed - some SQL queries produce this type of value.