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...
To uninstall Oracle database on Windows, we have to delete the all the related Ora* registry keys, files and folders manually. P.S Tested with Oracle database 19c on Windows 10 Note I can’t find any uninstaller to uninstall the Oracle database automatically? 1. Stop Oracle* services Press Windows key, type services, stop all Oracle related services. 2. Delete Oracle* registry...
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...
Since Java 1.6, JDBC 4.0 API, it provides a new feature to discover java.sql.Driver automatically, it means the Class.forName is no longer required. Just put any JDBC 4.x driver in the project classpath, and Java is able to detect it. For example, JDBC driver for...
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 this tutorial, we will show you how to use Logback in Spring Boot framework. Technologies used : Spring Boot 2.1.2.RELEASE Spring 5.1.4.RELEASE Logback 1.2.3 Maven 3 Java 8 1. Project Directory 2. Maven In Spring Boot, Logback is the default logging framework, just add spring-boot-starter-web, it will pull in the logback dependencies. pom.xml <?xml version="1.0"...
If Java 8, DateTimeFormatter, else SimpleDateFormat to change the date format in a String. 1. DateTimeFormatter (Java 8) Convert the String to LocalDateTime and change the date format with DateTimeFormatter DateFormatExample1.java package com.mkyong; import java.time.LocalDateTime; import java.time.format.DateTimeFormatter; public class DateFormatExample1 { // date format 1 ...
Different operating system has a different new line or line separator string: UNIX, Linux or Mac OSX = \n Windows = \r\n NewLineExample.java package com.mkyong; public class NewLineExample { public static void main(String[] args) { String original = "Hello World Java"; System.out.println(original); // add new line String originalNewLine =...
FastJson provides easily APIs to convert Java objects to / from JSON JSON.toJSONString – Java objects to JSON JSON.parseObject – JSON to Java objects JSON.parseArray – JSON array to List of Java objects Note You may have interest to read this How to parse JSON with Jackson Overall, the FastJson is really simple and easy to convert JSON to / from objects, however, it lack of...
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 Java, we have many ways to convert a File to a String. A text file for testing later. c:\\projects\\app.log A B C D E 1. Java 11 – Files.readString A new method Files.readString is added in java.nio.file.Files, it makes reading a string from File much easier. FileToString1.java package com.mkyong; import java.io.IOException; import java.nio.file.Files; import...
In Java, there are many ways to write a String to a File. 1. Java 11 – Files.writeString Finally, a new method added in java.nio to save a String into a File easily. StringToFileJava11.java package com.mkyong; import java.io.IOException; import java.nio.charset.StandardCharsets; import java.nio.file.Files; import java.nio.file.Paths; import...
In this tutorial, we will show you how to parse JSON with JSON.simple Note You may have interest to read – How to parse JSON with Jackson or Gson JSON.simple short history This project was formerly JSON.simple 1.x from a Google code project by Yidong, now maintaining by Clifton Labs, read this JSON.simple history P.S Tested with json-simple 3.1.0 1. Download...
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 =...
A Java example to generate a strong, secure random password containing [a-zA-Z0-9!@#$%&*()_+-=[]?] characters, with a length of 15. PasswordGenerator.java package com.mkyong; import java.security.SecureRandom; import java.util.Arrays; import java.util.Collections; import java.util.List; import java.util.stream.Collectors; public class PasswordGenerator { private static final...
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...
In Java, we can use Double.parseDouble() to convert a String to double 1. Double.parseDouble() Example to convert a String 3.142 to an primitive double. String str = "3.142"; double pi = Double.parseDouble(str); System.out.println(pi); Output 3.142 2. Double.valueOf() Example to convert a String 3.142 to an Double object. String str = "3.142"; Double pi =...
In Java, we can use new ArrayList(Arrays.asList(array)) to convert an Array into an ArrayList ArrayExample1.java package com.mkyong; import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class ArrayExample1 { public static void main(String[] args) { String[] str = {"A", "B", "C"}; List<String> list = new...
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...