Inserting BLOB Using Spring JdbcTemplate Example

1. Introduction

BLOB (Binary Large Object) is a large object data type in the database system. BLOB could store documents, images, audio, or video files. For smaller BLOBs, setting a byte array directly in memory is ok. For large BLOBs, streaming is more memory efficient. In this example, I will demonstrate how to use JdbcTemplate to insert and update a BLOB field in a PostgreSQL database.

2. Setup

In this step, I will create a Spring Boot (4.0.1) Java (21) project via Spring Initializer with PostgreSQL, Lombok, and JPA dependencies.

2.1 Build.gradle

Here is the generated build.gradle file.

build.gradle

plugins {
	id 'java'
	id 'org.springframework.boot' version '4.0.1'
	id 'io.spring.dependency-management' version '1.1.7'
}

group = 'org.jcg.zheng.demo'
version = '0.0.1-SNAPSHOT'
description = 'Demo project for BLOB'

java {
	toolchain {
		languageVersion = JavaLanguageVersion.of(21)
	}
}

repositories {
	mavenCentral()
}

dependencies {
	implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
  	compileOnly 'org.projectlombok:lombok'
  	runtimeOnly 'org.postgresql:postgresql'
  	annotationProcessor 'org.projectlombok:lombok'
 	testImplementation 'org.springframework.boot:spring-boot-starter-data-jpa-test'
 	testRuntimeOnly 'org.junit.platform:junit-platform-launcher'
}

tasks.named('test') {
	useJUnitPlatform()
}

2.2 InsertBlobApplication

Here is the generated InsertBlobApplication.java file.

InsertBlobApplication.java

package org.jcg.zheng.demo.insert_blob;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class InsertBlobApplication {

	public static void main(String[] args) {
		SpringApplication.run(InsertBlobApplication.class, args);
	}

}

2.3 Application Properties

Here is the updated application.properties file.

application.properties

spring.application.name=insert-blob

# DataSource configuration
spring.datasource.url=jdbc:postgresql://localhost:5432/postgres?currentSchema=marydb
spring.datasource.username=postgres
spring.datasource.password=
spring.datasource.driver-class-name=org.postgresql.Driver

logging.level.org.springframework.jdbc.core.JdbcTemplate=trace
logging.level.org.springframework.jdbc.core.StatementCreatorUtils=trace

• Line 9-10: enable the logging to show the raw SQL statement and binding parameters.

2.4 Start the Spring Boot Application

In this step, I will start the generated spring boot application and capture the server log.

Server Log

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/

 :: Spring Boot ::                (v4.0.1)

2026-01-16T20:32:26.077-06:00  INFO 2864 --- [insert-blob] [           main] o.j.z.d.i.InsertBlobApplication          : Starting InsertBlobApplication using Java 21.0.8 with PID 2864 (C:\MaryZheng\workspace\insert-blob-postgre\bin\main started by zzhen in C:\MaryZheng\workspace\insert-blob-postgre)
2026-01-16T20:32:26.081-06:00  INFO 2864 --- [insert-blob] [           main] o.j.z.d.i.InsertBlobApplication          : No active profile set, falling back to 1 default profile: "default"
2026-01-16T20:32:26.440-06:00  INFO 2864 --- [insert-blob] [           main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JPA repositories in DEFAULT mode.
2026-01-16T20:32:26.456-06:00  INFO 2864 --- [insert-blob] [           main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 10 ms. Found 0 JPA repository interfaces.
2026-01-16T20:32:26.617-06:00  INFO 2864 --- [insert-blob] [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2026-01-16T20:32:26.844-06:00  INFO 2864 --- [insert-blob] [           main] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Added connection org.postgresql.jdbc.PgConnection@64f16277
2026-01-16T20:32:26.846-06:00  INFO 2864 --- [insert-blob] [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
2026-01-16T20:32:26.942-06:00  INFO 2864 --- [insert-blob] [           main] org.hibernate.orm.jpa                    : HHH008540: Processing PersistenceUnitInfo [name: default]
2026-01-16T20:32:27.012-06:00  INFO 2864 --- [insert-blob] [           main] org.hibernate.orm.core                   : HHH000001: Hibernate ORM core version 7.2.0.Final
2026-01-16T20:32:27.535-06:00  INFO 2864 --- [insert-blob] [           main] o.s.o.j.p.SpringPersistenceUnitInfo      : No LoadTimeWeaver setup: ignoring JPA class transformer
2026-01-16T20:32:27.592-06:00  INFO 2864 --- [insert-blob] [           main] org.hibernate.orm.connections.pooling    : HHH10001005: Database info:
	Database JDBC URL [jdbc:postgresql://localhost:5432/postgres?currentSchema=marydb]
	Database driver: PostgreSQL JDBC Driver
	Database dialect: PostgreSQLDialect
	Database version: 18.0
	Default catalog/schema: postgres/marydb
	Autocommit mode: undefined/unknown
	Isolation level: READ_COMMITTED [default READ_COMMITTED]
	JDBC fetch size: none
	Pool: DataSourceConnectionProvider
	Minimum pool size: undefined/unknown
	Maximum pool size: undefined/unknown
2026-01-16T20:32:28.238-06:00  INFO 2864 --- [insert-blob] [           main] org.hibernate.orm.core                   : HHH000489: No JTA platform available (set 'hibernate.transaction.jta.platform' to enable JTA platform integration)
2026-01-16T20:32:28.246-06:00  INFO 2864 --- [insert-blob] [           main] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default'
2026-01-16T20:32:28.436-06:00  INFO 2864 --- [insert-blob] [           main] o.j.z.d.i.InsertBlobApplication          : Started InsertBlobApplication in 2.647 seconds (process running for 2.928)
2026-01-16T20:32:28.446-06:00  INFO 2864 --- [insert-blob] [ionShutdownHook] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'
2026-01-16T20:32:28.449-06:00  INFO 2864 --- [insert-blob] [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2026-01-16T20:32:28.452-06:00  INFO 2864 --- [insert-blob] [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

• Line 21: shows the Spring boot application using the PostgreSQL database as the configuration file specified.

3. PostgreSQL Database Table with a BLOB Column

In this step, I will create a table with a BLOB column in a PostgreSQL database:

Create Table SQL

 create table demo_blob_table (
        id integer not null,
        content_type varchar(255),
        blob_col bytea,
        primary key (id)
    );

• Line 4: The PostgreSQL bytea data type is used to map to a BLOB object.
• Note: use different storage systems when a bytea field exceeds 1 GB.

3.1 Create a Java Entity

In this example, I will create the BlobMeta.java that maps to a database table for non-BLOB fields.

BlobMeta.java

package org.jcg.zheng.demo.insert_blob.entity;

import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.Table;
import lombok.Data;

@Entity
@Table(name="demo_blob_table")
@Data
public class BlobMeta {
	
	@Id
	private Integer id;
	private String contentType;

}

• Line 9: the BlobMeta entity is mapped to table demo_blob_table without BLOB fields to reduce memory usage as JPA caches objects in memory.

4. Spring JdbcTemplate Insert BLOB

In this step, I will create an InsertBlobService.java that inserts or updates a BLOB column with the following methods:

• insert_with_ByteArray: insert a BLOB as byte[] directly using Spring JDBC.
• insert_with_bytes: insert a BLOB with the setBytes() method that sets the designated parameter to the given Java array of bytes when BLOB data is less than 1 MB.
• insert_with_BinaryStream: insert a BLOB and use the setBinaryStream method to set the designated parameter to the given input stream. It’s good when BLOB data is greater than 1 MB and less than 1 GB.
• insert_with_SQLVarbinary: insert a BLOB using Spring JDBC, explicitly treating the bytes array as SqlParameterValue(Types.VARBINARY) so the database stores it correctly.
• readBlob_asObject: read a BLOB via the JdbcTemplate.queryForObject method. The return data is in memory. it’s ok for smaller BLOB objects.
• readBlob_asStream: read a BLOB via the JdbcTemplate.queryForStream method. It streams into the InputStream and then writes to a file. It’s more memory efficient.
• update_with_bytes: update a BLOC via the setBytes method.

InsertBlobService.java

package org.jcg.zheng.demo.insert_blob.service;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;
import java.sql.PreparedStatement;
import java.sql.Types;
import java.util.stream.Stream;

import org.jcg.zheng.demo.insert_blob.entity.BlobMeta;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.SqlParameterValue;
import org.springframework.stereotype.Service;

import jakarta.transaction.Transactional;

@Service
@Transactional
public class InsertBlobService {

	private static final String SELECT_BLOB_SQL = "SELECT blob_col from demo_blob_table WHERE id=?";
	private static final String UPDATE_BLOB_SQL = "UPDATE demo_blob_table set blob_col=? WHERE id=?";
	private static final String INSERT_BLOB_SQL = "INSERT INTO demo_blob_table(id, content_type, blob_col) VALUES (?,?,?)";

	private final JdbcTemplate jdbcTemplate;

	public InsertBlobService(JdbcTemplate jdbcTemplate) {
		super();
		this.jdbcTemplate = jdbcTemplate;
	}

	public void insert_with_ByteArray(BlobMeta blobMeta, byte[] data) {
		jdbcTemplate.update(INSERT_BLOB_SQL, blobMeta.getId(), blobMeta.getContentType(), data);
	}

	public void insert_with_SQLVarbinary(BlobMeta blobMeta, byte[] data) {
		jdbcTemplate.update(INSERT_BLOB_SQL, blobMeta.getId(), blobMeta.getContentType(),
				new SqlParameterValue(Types.VARBINARY, data));
	}

	public void insert_with_BinaryStream(BlobMeta blobMeta, byte[] data) {
		jdbcTemplate.update(con -> {
			PreparedStatement ps = con.prepareStatement(INSERT_BLOB_SQL);
			ps.setInt(1, blobMeta.getId());
			ps.setString(2, blobMeta.getContentType());
			ps.setBinaryStream(3, new ByteArrayInputStream(data));
			return ps;
		});
	}

	public void insert_with_bytes(BlobMeta blobMeta, byte[] data) {
		jdbcTemplate.update(con -> {
			PreparedStatement ps = con.prepareStatement(INSERT_BLOB_SQL);
			ps.setInt(1, blobMeta.getId());
			ps.setString(2, blobMeta.getContentType());
			ps.setBytes(3, data);
			return ps;
		});
	}

	public byte[] readBlob_asObject(int id) {
		return jdbcTemplate.queryForObject(SELECT_BLOB_SQL, byte[].class, id);
	}

	public void readBlob_asStream(int id) {
		Path target = Paths.get("output.bin");
		try (Stream<InputStream> stream = jdbcTemplate.queryForStream(SELECT_BLOB_SQL,
				(rs, rowNum) -> rs.getBinaryStream("blob_col"), id)) {
			stream.findFirst().ifPresent(inputStream -> {

				try (InputStream in = inputStream) {
					Files.copy(in, target, StandardCopyOption.REPLACE_EXISTING);
				} catch (IOException e) {
					e.printStackTrace();
				}
			});

		}

	}

	public void update_with_bytes(int id, byte[] data) {
		jdbcTemplate.update(UPDATE_BLOB_SQL, ps -> {
			ps.setBytes(1, data);
			ps.setInt(2, id);
		});
	}

}

• Line 25-27: the raw SQL statements to insert, update, and select BLOB data.
• Line 37: map byte[] directly in the insert statement.
• Line 42: use SqlParameterValue(Types.VARBINARY) to map to byte[] to ensure correct JDBC type and avoid JDBC driver-specific issues. It prevents binary data being treated as VARCHAR and works across databases ( MySQL, SQL Server, Oracle, PostgreSQL).
• Line 50: setBinaryStream maps to InputStream for streaming into the database.
• Line 60: use setBytes maps to byte[].
• Line 66: queryForObject maps to byte[] in memory.
• Line 71: queryForStream maps to InputStream.
• Line 75: try-with-resources clause closes InputStream explicitly.
• Line 76: Files.copy writes the BLOB into a file.
• Line 88: setBytes is used in an update statement.

5. Test InsertBlobService

In this step, I will create a InsertBlobServiceTest.java that tests the methods to insert, update, and select a BLOB column.

InsertBlobServiceTest.java

package org.jcg.zheng.demo.insert_blob.service;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.jcg.zheng.demo.insert_blob.entity.BlobMeta;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

@SpringBootTest
class InsertBlobServiceTest {

	private static final String BLOB_STRING = "this is blob";
	private static final String BLOB_STRING_2 = "this is blob 2";
	@Autowired
	private InsertBlobService testClass;

	@Test
	void test_insert_with_BinaryStream() {
		int test_id = 2;

		testClass.insert_with_BinaryStream(testBlobMeta(test_id), BLOB_STRING.getBytes());

		byte[] ret = testClass.readBlob_asObject(test_id);

		assertEquals(BLOB_STRING, new String(ret));

	}

	@Test
	void test_insert_with_ByteArray() {
		int test_id = 1;

		testClass.insert_with_ByteArray(testBlobMeta(test_id), BLOB_STRING.getBytes());

		byte[] ret = testClass.readBlob_asObject(test_id);

		assertEquals(BLOB_STRING, new String(ret));
	
		testClass.readBlob_asStream(1);

	}

	@Test
	void test_insert_with_bytes() {
		int test_id = 3;

		testClass.insert_with_bytes(testBlobMeta(test_id), BLOB_STRING.getBytes());

		byte[] ret = testClass.readBlob_asObject(test_id);

		assertEquals(BLOB_STRING, new String(ret));

	}

	@Test
	void test_insert_with_SQLVarbinary() {
		int test_id = 4;

		testClass.insert_with_SQLVarbinary(testBlobMeta(test_id), BLOB_STRING.getBytes());

		byte[] ret = testClass.readBlob_asObject(test_id);

		assertEquals(BLOB_STRING, new String(ret));

	}

	
	@Test
	void test_update_with_bytes() {
		int test_id = 1;
		byte[] ret = testClass.readBlob_asObject(test_id);
		if (ret == null) {
			testClass.insert_with_ByteArray(testBlobMeta(test_id), BLOB_STRING.getBytes());
		}

		testClass.update_with_bytes(1, BLOB_STRING_2.getBytes());

		assertEquals(BLOB_STRING_2, new String(testClass.readBlob_asObject(1)));

	}

	private BlobMeta testBlobMeta(int id) {
		BlobMeta blobMeta = new BlobMeta();
		blobMeta.setId(id);
		blobMeta.setContentType("txt");
		return blobMeta;
	}
}

Run tests and capture output.

The console log shows the actual SQL statements and the binding parameters.

InsertBlobServiceTest Console Log

20:36:30.695 [main] INFO org.springframework.test.context.support.AnnotationConfigContextLoaderUtils -- Could not detect default configuration classes for test class [org.jcg.zheng.demo.insert_blob.service.InsertBlobServiceTest]: InsertBlobServiceTest does not declare any static, non-private, non-final, nested classes annotated with @Configuration.
20:36:30.773 [main] INFO org.springframework.boot.test.context.SpringBootTestContextBootstrapper -- Found @SpringBootConfiguration org.jcg.zheng.demo.insert_blob.InsertBlobApplication for test class org.jcg.zheng.demo.insert_blob.service.InsertBlobServiceTest

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/

 :: Spring Boot ::                (v4.0.1)

2026-01-16T20:36:31.076-06:00  INFO 26912 --- [insert-blob] [           main] o.j.z.d.i.service.InsertBlobServiceTest  : Starting InsertBlobServiceTest using Java 21.0.8 with PID 26912 (started by zzhen in C:\MaryZheng\workspace\insert-blob-postgre)
2026-01-16T20:36:31.076-06:00  INFO 26912 --- [insert-blob] [           main] o.j.z.d.i.service.InsertBlobServiceTest  : No active profile set, falling back to 1 default profile: "default"
2026-01-16T20:36:31.322-06:00  INFO 26912 --- [insert-blob] [           main] .s.d.r.c.RepositoryConfigurationDelegate : Bootstrapping Spring Data JPA repositories in DEFAULT mode.
2026-01-16T20:36:31.339-06:00  INFO 26912 --- [insert-blob] [           main] .s.d.r.c.RepositoryConfigurationDelegate : Finished Spring Data repository scanning in 8 ms. Found 0 JPA repository interfaces.
2026-01-16T20:36:31.520-06:00  INFO 26912 --- [insert-blob] [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Starting...
2026-01-16T20:36:31.696-06:00  INFO 26912 --- [insert-blob] [           main] com.zaxxer.hikari.pool.HikariPool        : HikariPool-1 - Added connection org.postgresql.jdbc.PgConnection@31f295b6
2026-01-16T20:36:31.697-06:00  INFO 26912 --- [insert-blob] [           main] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Start completed.
2026-01-16T20:36:31.778-06:00  INFO 26912 --- [insert-blob] [           main] org.hibernate.orm.jpa                    : HHH008540: Processing PersistenceUnitInfo [name: default]
2026-01-16T20:36:31.842-06:00  INFO 26912 --- [insert-blob] [           main] org.hibernate.orm.core                   : HHH000001: Hibernate ORM core version 7.2.0.Final
2026-01-16T20:36:32.239-06:00  INFO 26912 --- [insert-blob] [           main] o.s.o.j.p.SpringPersistenceUnitInfo      : No LoadTimeWeaver setup: ignoring JPA class transformer
2026-01-16T20:36:32.327-06:00  INFO 26912 --- [insert-blob] [           main] org.hibernate.orm.connections.pooling    : HHH10001005: Database info:
	Database JDBC URL [jdbc:postgresql://localhost:5432/postgres?currentSchema=marydb]
	Database driver: PostgreSQL JDBC Driver
	Database dialect: PostgreSQLDialect
	Database version: 18.0
	Default catalog/schema: postgres/marydb
	Autocommit mode: undefined/unknown
	Isolation level: READ_COMMITTED [default READ_COMMITTED]
	JDBC fetch size: none
	Pool: DataSourceConnectionProvider
	Minimum pool size: undefined/unknown
	Maximum pool size: undefined/unknown
2026-01-16T20:36:32.899-06:00  INFO 26912 --- [insert-blob] [           main] org.hibernate.orm.core                   : HHH000489: No JTA platform available (set 'hibernate.transaction.jta.platform' to enable JTA platform integration)
2026-01-16T20:36:32.905-06:00  INFO 26912 --- [insert-blob] [           main] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default'
2026-01-16T20:36:33.074-06:00  INFO 26912 --- [insert-blob] [           main] o.j.z.d.i.service.InsertBlobServiceTest  : Started InsertBlobServiceTest in 2.187 seconds (process running for 3.087)
Mockito is currently self-attaching to enable the inline-mock-maker. This will no longer work in future releases of the JDK. Please add Mockito as an agent to your build as described in Mockito's documentation: https://javadoc.io/doc/org.mockito/mockito-core/latest/org.mockito/org/mockito/Mockito.html#0.3
WARNING: A Java agent has been loaded dynamically (C:\Users\zzhen\.gradle\caches\modules-2\files-2.1\net.bytebuddy\byte-buddy-agent\1.17.8\f09415827a71be7ed621c7bd02550678f28bc81c\byte-buddy-agent-1.17.8.jar)
WARNING: If a serviceability tool is in use, please run with -XX:+EnableDynamicAgentLoading to hide this warning
WARNING: If a serviceability tool is not in use, please run with -Djdk.instrument.traceUsage for more information
WARNING: Dynamic loading of agents will be disallowed by default in a future release
OpenJDK 64-Bit Server VM warning: Sharing is only supported for boot loader classes because bootstrap classpath has been appended
2026-01-16T20:36:33.443-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL update
2026-01-16T20:36:33.443-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL statement [INSERT INTO demo_blob_table(id, content_type, blob_col) VALUES (?,?,?)]
2026-01-16T20:36:33.450-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 1, parameter value [4], value class [java.lang.Integer], SQL type unknown
2026-01-16T20:36:33.450-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 2, parameter value [txt], value class [java.lang.String], SQL type unknown
2026-01-16T20:36:33.451-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 3, parameter value [[B@2604940], value class [[B], SQL type -3
2026-01-16T20:36:33.453-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : SQL update affected 1 rows
2026-01-16T20:36:33.461-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL query
2026-01-16T20:36:33.463-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL statement [SELECT blob_col from demo_blob_table WHERE id=?]
2026-01-16T20:36:33.463-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 1, parameter value [4], value class [java.lang.Integer], SQL type unknown
2026-01-16T20:36:33.473-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL update
2026-01-16T20:36:33.473-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL statement
2026-01-16T20:36:33.473-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : SQL update affected 1 rows
2026-01-16T20:36:33.477-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL query
2026-01-16T20:36:33.477-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL statement [SELECT blob_col from demo_blob_table WHERE id=?]
2026-01-16T20:36:33.477-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 1, parameter value [3], value class [java.lang.Integer], SQL type unknown
2026-01-16T20:36:33.480-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL update
2026-01-16T20:36:33.480-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL statement [INSERT INTO demo_blob_table(id, content_type, blob_col) VALUES (?,?,?)]
2026-01-16T20:36:33.480-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 1, parameter value [1], value class [java.lang.Integer], SQL type unknown
2026-01-16T20:36:33.480-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 2, parameter value [txt], value class [java.lang.String], SQL type unknown
2026-01-16T20:36:33.480-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 3, parameter value [[B@c8ed958], value class [[B], SQL type unknown
2026-01-16T20:36:33.481-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : SQL update affected 1 rows
2026-01-16T20:36:33.482-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL query
2026-01-16T20:36:33.482-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL statement [SELECT blob_col from demo_blob_table WHERE id=?]
2026-01-16T20:36:33.482-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 1, parameter value [1], value class [java.lang.Integer], SQL type unknown
2026-01-16T20:36:33.484-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL statement [SELECT blob_col from demo_blob_table WHERE id=?]
2026-01-16T20:36:33.484-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 1, parameter value [1], value class [java.lang.Integer], SQL type unknown
2026-01-16T20:36:33.489-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL query
2026-01-16T20:36:33.489-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL statement [SELECT blob_col from demo_blob_table WHERE id=?]
2026-01-16T20:36:33.489-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 1, parameter value [1], value class [java.lang.Integer], SQL type unknown
2026-01-16T20:36:33.490-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL update
2026-01-16T20:36:33.490-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL statement [UPDATE demo_blob_table set blob_col=? WHERE id=?]
2026-01-16T20:36:33.491-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : SQL update affected 1 rows
2026-01-16T20:36:33.492-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL query
2026-01-16T20:36:33.492-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL statement [SELECT blob_col from demo_blob_table WHERE id=?]
2026-01-16T20:36:33.492-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 1, parameter value [1], value class [java.lang.Integer], SQL type unknown
2026-01-16T20:36:33.495-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL update
2026-01-16T20:36:33.495-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL statement
2026-01-16T20:36:33.496-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : SQL update affected 1 rows
2026-01-16T20:36:33.496-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL query
2026-01-16T20:36:33.496-06:00 DEBUG 26912 --- [insert-blob] [           main] o.s.jdbc.core.JdbcTemplate               : Executing prepared SQL statement [SELECT blob_col from demo_blob_table WHERE id=?]
2026-01-16T20:36:33.497-06:00 TRACE 26912 --- [insert-blob] [           main] o.s.jdbc.core.StatementCreatorUtils      : Setting SQL statement parameter value: column index 1, parameter value [2], value class [java.lang.Integer], SQL type unknown
2026-01-16T20:36:33.505-06:00  INFO 26912 --- [insert-blob] [ionShutdownHook] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'
2026-01-16T20:36:33.507-06:00  INFO 26912 --- [insert-blob] [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2026-01-16T20:36:33.512-06:00  INFO 26912 --- [insert-blob] [ionShutdownHook] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.

6. Conclusion

In this example, I demonstrated several ways to insert, update, and select a BLOB field in the PostgreSQL database.

• PreparedStatement.setBytes: sets the designated parameter to the given Java array of bytes. It’s good when BLOB data is less than 1 MB.
• PreparedStatement.setBinaryStream: sets the designated parameter to the given input stream. It’s good when BLOB data is greater than 1 MB and less than 1 GB.
• SqlParameterValue(Types.VARBINARY): sets an SQL parameter value for BLOB to avoid JDBC driver issues.
• JdbcTemplate.queryForStream: read result as Stream for BLOB for better memory management.

7. Download

This was an example of inserting BLOB fields via Spring JdbcTemplate.

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