Below example, the jdbcTemplate.queryForList returns an object of Integer and we try to convert it into a Long directly: public List<Customer> findAll() { String sql = "SELECT * FROM CUSTOMER"; List<Customer> customers = new ArrayList<>(); List<Map<String, Object>> rows = jdbcTemplate.queryForList(sql); for (Map row :...
Some Java Conferences and Events 2019. 1. JAX London (October 7–10, 2019) JAX London is a four-day conference for cutting edge software engineers and enterprise-level professionals. JAX brings together the world’s leading innovators in the fields of JAVA, microservices, continuous delivery and DevOps. Date: October 7–10, 2019 Location: Business Design Centre, London Discount(15%):...
This is caused by the requested SID doesn’t exist in {ORACLE_HOME}/network/admin/tnsnames.ora P.S Tested with Oracle database 19c with ojdbc8.jar 1. JDBC try (Connection conn = DriverManager.getConnection( "jdbc:oracle:thin:@localhost:1521:xe", "system", "password")) { //... } catch (SQLException e) { e.printStackTrace(); } catch (Exception...
A JDBC CallableStatement example to show you how to call a stored function from PostgreSQL database. P.S Tested with PostgreSQL 11 and Java 8 pom.xml <dependency> <groupId>org.postgresql</groupId> <artifactId>postgresql</artifactId> <version>42.2.5</version> </dependency> 1. Call Function 1.1 Create a stored function and calling it...
A JDBC example to connect to a PostgreSQL, and print out all the tables from the default database postgres pom.xml <dependencies> <dependency> <groupId>org.postgresql</groupId> <artifactId>postgresql</artifactId> <version>42.2.5</version> </dependency> </dependencies> P.S...
In Java, -Xms set initial Java heap size, while -Xmx set the maximum Java heap size. 1. Some java -Xms -Xmx examples : # Start with 128MB of memory, and allow the Java process to use up to 1024MB of memory. java -Xms128m -Xmx1024m # Start with 256MB of memory, and allow the Java process to use up to 4G (4096MB) of memory. java -Xms256m -Xmx4g 2. The default initial and maximum Java...
Only Streams whose source are an IO channel like Files.lines(Path, Charset) need to be closed. Read this Stream JavaDocs Streams have a BaseStream.close() method and implement AutoCloseable, but nearly all stream instances do not actually need to be closed after use. Generally, only streams whose source is an IO channel (such as those returned by Files.lines(Path, Charset)) will require closing....
In this tutorial, we will show you how to use Jackson 2.x to convert Java objects to / from a JSON. 1. Basic 1.1 Convert a Staff object to from JSON. writeValue(...) – Java Objects to JSON ObjectMapper mapper = new ObjectMapper(); // Java object to JSON file mapper.writeValue(new File("c:\\test\\staff.json"), new Staff()); // Java object to JSON string String jsonString =...
Few Java examples to show you how to generate a random alphanumeric String, with a fixed length. 1. Random [a-ZA-Z0-9] 1.1 Generate a random alphanumeric String [a-ZA-Z0-9], with a length of 8. RandomExample.java package com.mkyong; import java.security.SecureRandom; public class RandomExample { private static final String CHAR_LOWER = "abcdefghijklmnopqrstuvwxyz"; private...
Here are a few logback.xml examples that are used in my projects, just for sharing. P.S Tested with Logback 1.2.3 1. Send logs to Console All logging will be redirected to console. logback.xml <configuration> <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender"> <layout class="ch.qos.logback.classic.PatternLayout"> <Pattern> ...
In this tutorial, we will show you how to use Apache Log4j 2 in Spring Boot framework. Technologies used : Spring Boot 2.1.2.RELEASE Spring 5.1.4.RELEASE Log4j 2.11.1 Maven 3 Java 8 1. Project Directory 2. Maven The key is exclude the default logback, and include log4j with spring-boot-starter-log4j2 pom.xml <?xml version="1.0" encoding="UTF-8"?> <project...
