Add support to build JsonItemReader when no Resource is provided

Resolves #3731

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/json/JsonItemReader.java

@@ -73,6 +73,9 @@ public class JsonItemReader<T> extends AbstractItemCountingItemStreamItemReader<
 		this.jsonObjectReader = jsonObjectReader;
 		setExecutionContextName(ClassUtils.getShortName(JsonItemReader.class));
 	}
+	public JsonItemReader(){
+		setExecutionContextName(ClassUtils.getShortName(JsonItemReader.class));
+	}
 
 	/**
 	 * Set the {@link JsonObjectReader} to use to read and map Json fragments to domain objects.

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/json/builder/JsonItemReaderBuilder.java

@@ -140,12 +140,13 @@ public class JsonItemReaderBuilder<T> {
 	 */
 	public JsonItemReader<T> build() {
 		Assert.notNull(this.jsonObjectReader, "A json object reader is required.");
-		Assert.notNull(this.resource, "A resource is required.");
 		if (this.saveState) {
 			Assert.state(StringUtils.hasText(this.name), "A name is required when saveState is set to true.");
 		}
 
-		JsonItemReader<T> reader = new JsonItemReader<>(this.resource, this.jsonObjectReader);
+		JsonItemReader<T> reader = new JsonItemReader<>();
+		reader.setResource(this.resource);
+		reader.setJsonObjectReader(this.jsonObjectReader);
 		reader.setName(this.name);
 		reader.setStrict(this.strict);
 		reader.setSaveState(this.saveState);

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/json/builder/JsonItemReaderBuilderTest.java

@@ -57,17 +57,6 @@ public class JsonItemReaderBuilderTest {
 					iae.getMessage());
 		}
 
-		try {
-			new JsonItemReaderBuilder<String>()
-					.jsonObjectReader(this.jsonObjectReader)
-					.build();
-			fail("A resource is required.");
-		}
-		catch (IllegalArgumentException iae) {
-			assertEquals("A resource is required.",
-					iae.getMessage());
-		}
-
 		try {
 			new JsonItemReaderBuilder<String>()
 					.jsonObjectReader(this.jsonObjectReader)
@@ -102,4 +91,24 @@ public class JsonItemReaderBuilderTest {
 		Object executionContext = getField(itemReader, "executionContextUserSupport");
 		Assert.assertEquals("jsonItemReader", getField(executionContext, "name"));
 	}
+	@Test
+	public void shouldBuildJsonItemReaderWhenResourceIsNotProvided(){
+	    JsonItemReader<String> itemReader = new JsonItemReaderBuilder<String>()
+                .jsonObjectReader(this.jsonObjectReader)
+                .saveState(true)
+                .strict(true)
+                .name("jsonItemReader")
+                .maxItemCount(100)
+                .currentItemCount(50)
+                .build();
+
+			Assert.assertEquals(this.jsonObjectReader, getField(itemReader, "jsonObjectReader"));
+			Assert.assertEquals(100, getField(itemReader, "maxItemCount"));
+			Assert.assertEquals(50, getField(itemReader, "currentItemCount"));
+			Assert.assertTrue((Boolean) getField(itemReader, "saveState"));
+			Assert.assertTrue((Boolean) getField(itemReader, "strict"));
+			Object executionContext = getField(itemReader, "executionContextUserSupport");
+			Assert.assertEquals("jsonItemReader", getField(executionContext, "name"));
+
+	}
 }