Fix compiler warnings

- Add `@Nullable` where needed
- Suppress warnings where appropriate
- Add generic type definitions

spring-batch-core/src/main/java/org/springframework/batch/core/converter/DefaultJobParametersConverter.java

@@ -153,6 +153,7 @@ public class DefaultJobParametersConverter implements JobParametersConverter {
 	 * @param encodedJobParameter the encoded job parameter
 	 * @return the decoded job parameter
 	 */
+	@SuppressWarnings(value = { "unchecked", "rawtypes" })
 	protected JobParameter<?> decode(String encodedJobParameter) {
 		String parameterStringValue = parseValue(encodedJobParameter);
 		Class<?> parameterType = parseType(encodedJobParameter);

spring-batch-core/src/main/java/org/springframework/batch/core/converter/JsonJobParametersConverter.java

@@ -100,6 +100,7 @@ public class JsonJobParametersConverter extends DefaultJobParametersConverter {
 		}
 	}
 
+	@SuppressWarnings(value = { "unchecked", "rawtypes" })
 	@Override
 	protected JobParameter decode(String encodedJobParameter) {
 		try {

spring-batch-core/src/main/java/org/springframework/batch/core/repository/dao/Jackson2ExecutionContextStringSerializer.java

@@ -212,6 +212,7 @@ public class Jackson2ExecutionContextStringSerializer implements ExecutionContex
 				super(JobParameter.class);
 			}
 
+			@SuppressWarnings(value = { "unchecked", "rawtypes" })
 			@Override
 			public JobParameter deserialize(JsonParser parser, DeserializationContext context) throws IOException {
 				JsonNode node = parser.readValueAsTree();

spring-batch-core/src/main/java/org/springframework/batch/core/repository/dao/JdbcJobExecutionDao.java

@@ -414,6 +414,7 @@ public class JdbcJobExecutionDao extends AbstractJdbcBatchMetadataDao implements
 	 * Convenience method that inserts all parameters from the provided JobParameters.
 	 *
 	 */
+	@SuppressWarnings(value = { "unchecked", "rawtypes" })
 	private void insertJobParameters(Long executionId, JobParameters jobParameters) {
 
 		if (jobParameters.isEmpty()) {
@@ -450,6 +451,7 @@ public class JdbcJobExecutionDao extends AbstractJdbcBatchMetadataDao implements
 	 * @param executionId {@link Long} containing the id for the execution.
 	 * @return job parameters for the requested execution id
 	 */
+	@SuppressWarnings(value = { "unchecked", "rawtypes" })
 	protected JobParameters getJobParameters(Long executionId) {
 		final Map<String, JobParameter<?>> map = new HashMap<>();
 		RowCallbackHandler handler = rs -> {

spring-batch-core/src/main/java/org/springframework/batch/core/step/builder/FaultTolerantStepBuilder.java

@@ -189,6 +189,7 @@ public class FaultTolerantStepBuilder<I, O> extends SimpleStepBuilder<I, O> {
 	 * @param listener the object that has a method configured with listener annotation
 	 * @return this for fluent chaining
 	 */
+	@SuppressWarnings("unchecked")
 	@Override
 	public FaultTolerantStepBuilder<I, O> listener(Object listener) {
 		super.listener(listener);
@@ -201,7 +202,7 @@ public class FaultTolerantStepBuilder<I, O> extends SimpleStepBuilder<I, O> {
 		if (skipListenerMethods.size() > 0) {
 			StepListenerFactoryBean factory = new StepListenerFactoryBean();
 			factory.setDelegate(listener);
-			skipListeners.add((SkipListener) factory.getObject());
+			skipListeners.add((SkipListener<I, O>) factory.getObject());
 		}
 
 		return this;