Consistently introspect constructor-provided JmsTemplate

See gh-32501

spring-jms/src/main/java/org/springframework/jms/core/JmsMessagingTemplate.java

@@ -59,7 +59,7 @@ public class JmsMessagingTemplate extends AbstractMessagingTemplate<Destination>
 
 	private @Nullable JmsOperations jmsTemplate;
 
-	private MessageConverter jmsMessageConverter = new MessagingMessageConverter();
+	private MessageConverter jmsMessageConverter;
 
 	private boolean converterSet;
 
@@ -71,6 +71,7 @@ public class JmsMessagingTemplate extends AbstractMessagingTemplate<Destination>
 	 * Requires {@link #setConnectionFactory} or {@link #setJmsTemplate} to be called.
 	 */
 	public JmsMessagingTemplate() {
+		this.jmsMessageConverter = new MessagingMessageConverter();
 	}
 
 	/**
@@ -79,7 +80,16 @@ public class JmsMessagingTemplate extends AbstractMessagingTemplate<Destination>
 	 * @since 4.1.2
 	 */
 	public JmsMessagingTemplate(ConnectionFactory connectionFactory) {
-		this.jmsTemplate = new JmsTemplate(connectionFactory);
+		this(new JmsTemplate(connectionFactory));
+	}
+
+	/**
+	 * Create a {@code JmsMessagingTemplate} instance with the {@link JmsTemplate} to use.
+	 */
+	public JmsMessagingTemplate(JmsTemplate jmsTemplate) {
+		Assert.notNull(jmsTemplate, "JmsTemplate must not be null");
+		this.jmsTemplate = jmsTemplate;
+		this.jmsMessageConverter = new MessagingMessageConverter(jmsTemplate.getMessageConverter());
 	}
 
 	/**
@@ -89,13 +99,8 @@ public class JmsMessagingTemplate extends AbstractMessagingTemplate<Destination>
 	public JmsMessagingTemplate(JmsOperations jmsTemplate) {
 		Assert.notNull(jmsTemplate, "JmsTemplate must not be null");
 		this.jmsTemplate = jmsTemplate;
-	}
-
-	/**
-	 * Create a {@code JmsMessagingTemplate} instance with the {@link JmsTemplate} to use.
-	 */
-	public JmsMessagingTemplate(JmsTemplate jmsTemplate) {
-		this((JmsOperations) jmsTemplate);
+		this.jmsMessageConverter = (jmsTemplate instanceof JmsTemplate template ?
+				new MessagingMessageConverter(template.getMessageConverter()) : new MessagingMessageConverter());
 	}
 
 
@@ -104,8 +109,10 @@ public class JmsMessagingTemplate extends AbstractMessagingTemplate<Destination>
 	 * @since 4.1.2
 	 */
 	public void setConnectionFactory(ConnectionFactory connectionFactory) {
-		if (this.jmsTemplate instanceof JmsAccessor template) {
+		if (this.jmsTemplate instanceof JmsAccessor accessor) {
+			JmsTemplate template = new JmsTemplate(accessor);
 			template.setConnectionFactory(connectionFactory);
+			this.jmsTemplate = template;
 		}
 		else {
 			this.jmsTemplate = new JmsTemplate(connectionFactory);

spring-jms/src/test/java/org/springframework/jms/core/JmsClientTests.java

@@ -42,6 +42,7 @@ import org.mockito.stubbing.Answer;
 import org.springframework.jms.InvalidDestinationException;
 import org.springframework.jms.MessageNotReadableException;
 import org.springframework.jms.StubTextMessage;
+import org.springframework.jms.support.converter.SimpleMessageConverter;
 import org.springframework.jms.support.destination.DestinationResolutionException;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessagingException;
@@ -70,7 +71,7 @@ class JmsClientTests {
 	@Captor
 	private ArgumentCaptor<MessageCreator> messageCreator;
 
-	@Mock
+	@Mock(strictness = Mock.Strictness.LENIENT)
 	private JmsTemplate jmsTemplate;
 
 	private JmsClient jmsClient;
@@ -78,6 +79,7 @@ class JmsClientTests {
 
 	@BeforeEach
 	void setup() {
+		given(this.jmsTemplate.getMessageConverter()).willReturn(new SimpleMessageConverter());
 		this.jmsClient = JmsClient.create(this.jmsTemplate);
 	}
 

spring-jms/src/test/java/org/springframework/jms/core/JmsMessagingTemplateTests.java

@@ -80,6 +80,7 @@ class JmsMessagingTemplateTests {
 
 	@BeforeEach
 	void setup() {
+		given(this.jmsTemplate.getMessageConverter()).willReturn(new SimpleMessageConverter());
 		this.messagingTemplate = new JmsMessagingTemplate(this.jmsTemplate);
 	}
 
@@ -93,7 +94,6 @@ class JmsMessagingTemplateTests {
 		MessageConverter messageConverter = mock();
 		given(this.jmsTemplate.getMessageConverter()).willReturn(messageConverter);
 		JmsMessagingTemplate messagingTemplate = new JmsMessagingTemplate(this.jmsTemplate);
-		messagingTemplate.afterPropertiesSet();
 		assertPayloadConverter(messagingTemplate, messageConverter);
 	}
 
@@ -174,9 +174,6 @@ class JmsMessagingTemplateTests {
 
 	@Test
 	void sendPropertyInjection() {
-		MessageConverter messageConverter = new SimpleMessageConverter();
-		given(this.jmsTemplate.getMessageConverter()).willReturn(messageConverter);
-
 		this.messagingTemplate = new JmsMessagingTemplate();
 		this.messagingTemplate.setJmsTemplate(this.jmsTemplate);
 		this.messagingTemplate.setDefaultDestinationName("myQueue");