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Security Test-Driven – Learning by Pain

Vom Code in die Cloud mit Mvn, Springboot, Docker und Kubernetes

A tool to convert CSV, YML, XML, JSON and JSON-LD – oi v0.1

First release of oi is ready for testing. oi is an experimental command line tool to convert structured data from one format into another. The first release comes with rudimentary support for CSV, JSON, XML, YML and JSON-LD. The basic idea is to provide a straight in-out/out-in command that might not work completely correct but complements with other tools (jq, xsltproc,  sed, grep, awk, etc. ) to manipulate structured data on the command line.


sudo apt install ./oi_0.0.1.deb # installs openjdk-11-jre

Example Usage

  1. Convert passwd to yml (use -t to print different formats)
oi /etc/passwd -d":" --header="login,password,uid,gid,comment,home,shell" -icsv
  1. List some disk info in yml (use -t to print different formats)
lsblk |grep -o sd.*|awk '{print $1 ";" $4 ";" $NF}'|oi -d";" --header="device,size,mount" -icsv
  1. Create adhoc Json-Ld Context for some arbitrary Json-API
curl|oi -ijson -tcontext

Java: Simple Read/Write of Maps as Json

You can use tools like Jackson to serialize and deserialize maps to json an vice versa.


public void loadMapFromFileAndSaveIt(){
    Map<Object, Object> map = loadMap("map.json");
    map.put("8", "8th");

private Map<Object, Object> loadMap(String string) {
    ObjectMapper mapper = new ObjectMapper(); //should be initialized outside!
    try (InputStream in = Thread.currentThread().getContextClassLoader().getResourceAsStream("map.json")) {
        return mapper.readValue(in, HashMap.class);
    }catch (Exception e) {
        throw new RuntimeException(e);

private void saveMap(Map<Object, Object> map,String path) {
    try (PrintWriter out = new PrintWriter(path)) {
    } catch (Exception e) {
        throw new RuntimeException(e);

public String toString(Object obj) {
    try (StringWriter w = new StringWriter();) {
        new ObjectMapper().configure(SerializationFeature.INDENT_OUTPUT, true).writeValue(w, obj);
        return w.toString();
    } catch (Exception e) {
        throw new RuntimeException(e);

If the file map.json on your classpath contains


The code above will modify it and writes it to a file /path/to/map2.txt that will contain the modified map.

  "1" : "1th",
  "2" : "2th",
  "3" : "3th",
  "4" : "4th",
  "5" : "5th",
  "6" : "6th",
  "8" : "8th"


JPackage – Launch Java Apps without JVM

The jpackage tool of Java 14 can be used to create platform specific packages of java apps.  The app does not require a JVM to run.


/opt/jdk-14/bin/jpackage --name etctoy --input target --main-jar etctoy.jar

The call is made from within a maven project. etctoy.jar is a fat-jar (size 6.6M) but the call should also work for regular jars with further dependencies in the target directory (see –input parameter).

The result is a debian package that installs the app under /opt/etctoy

sudo dpkg -i etctoy_1.0-1_amd64.deb

The installation uses 140M of disk space.

To make the tool available via command line on should link the binary into /usr/bin

sudo ln -s /opt/etctoy/bin/etctoy /usr/bin