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  Generate certificate in Java -- Store certificate in KeyStore

In previous post, we have explained how to create a certificate chain in Java. After generating the chain, we need to store it somewhere so that it can be used later when we are doing the actual SSL communication, either in a key store or trust store. This post will show you how to store the private key and its associated certificate chain in a keystore file. There are different types of keystore in Java, in this post, we will choose the JKS to demonstrate how to store the certificate chain. Whe...

   Java,Certificate chain,Keystore     2014-08-20 03:56:39

  Different types of keystore in Java -- JKS

JKS is Java Keystore, a proprietary keystore type designed for Java. It can be used to store private keys and certificates used for SSL communication, it cannot store secret keys however. The keytool shipped with JDKs cannot extract private keys stored on JKS. This type of keystore usually has an extension of jks. Next we will show how to operate the JKS keystore with pure Java code. Create JKS keystore The simplest method to create a JKS keystore to create an empty keystore. We can first get an...

   DEMO,EXAMPLE,KEYSTORE,JKS     2014-09-05 20:21:51

  Top 10 essential Java classes

When we write Java programs, we will frequently use some classes such as java.lang.String. There are some essential Java classes which we may use frequently, there is no strict rules for the selection of essential Java classes, in fact there are no rules followed. It depends on what projects you are doing or what you have done,, so every one may have his own choices about the top essential Java classes in his mind. Here we list the top 10 essential Java classes you may agree with.1. java.lang.St...

   Java,class,essential class,top 10     2012-06-04 09:44:19

  Do you have this kind of comments in your source code?

Writing runnable code is the essential skill of a programmer, writing understandable comment is also a skill a programmer should acquire. There is some famous saying that bad comment is worth than no comment. Usually your code will be maintained by other people, if you provide them some difficult to understand or misguided comments, this will be nightmare to them. While at some other time, programmers may put some funny comments in their codes which may make others laugh. Today we...

   COMMENT,HUMOR     2016-08-01 10:25:14

  Memory related exception analysis in Java

Java Virtual Machine Specification divides the memory of JVM into several areas : Heap, Stack, The Program Counter register and Method area etc. In HotSpot JVM, heap is composed of Young, Tenured and Perm. There are different OutOfMemory error can happen in different memory area. Next is an overview of some of these OOM errors. StackOverflowError The JVM will allow only a specified number of stacks created nested. An JVM option -Xss can be set to determine the maximum stack size. If the num...

   Java, Memory model, Memory exception, OOM     2015-01-19 06:54:27

  A HTTPS client and HTTPS server demo in Java

In this post, I will create a HTTPS server and HTTPS client demo which can establish HTTPS communication between a server and a client using Java. This should be very useful when we want to test our understanding about SSL communication. We will use both a detailed SSL client and a simple HttpsURLConnection as the HTTPS client. Before creating the actual HTTPS server and HTTPS client, we first need to generate the keystore and truststore to be used by the server and client. To generate the keyst...

   SSL,HTTPS,JAVA,DEMO     2015-10-23 09:04:36

  Access control in Java -- doPrivileged

Previously we have introduced how Java performs permission check to protect resource access. What if sometimes we need to give some class the temporary access to some resource which it initially doesn't have? AccessController provides six doPrivileged methods to fulfill this requirement. These six methods have below signatures : static T doPrivileged(PrivilegedAction action)static T doPrivileged(PrivilegedAction action, AccessControlContext context)static T doPrivileged(PrivilegedExceptionA...

   JAVA,SECURITY,DOPRIVILEGED     2016-03-08 05:46:42

  To our youth

Youth is the best period in our life for most of us. We have dreams, passions and energies. We can work day and night for our dreams.We can hang out with friends the whole day. But there will always be a day when we are not young anymore, our youth will pass by. We will not be able to go back to our youth any more. Do you have anything to say about your youth? Recently, a Chinese IT engineer @本座 wrote a short code snippet to describe our youth. Here we share what she writes: public vo...

   Youth,Programming,Rollback     2013-05-02 05:26:56

  Solve Hibernate "Too many connections" issue in MySQL

When working with Hibernate and MySQL, sometimes some exceptions will be thrown after sometime. The exception may seem like : java.sql.SQLException: Data source rejected establishment of connection, message from server: "Too many connections" This means there are too many active connections on the MySQL, you can use SHOW STATUS LIKE '%Threads_connected%'; to check the active connections to MySQL. If you want to change the maximum connections allowed to MySQL. You can execute: set global max_co...

   MySQL,Hibernate,Clos     2013-09-04 22:20:49

  The difference between System.load and System.loadLibrary in Java

When writing code using native library in Java, normally the first step is loading some native library. static{ 　　System.load("D:" + File.separator + "Hello.dll"); } JDK provides two ways to load libraries: System.load(String filename) System.loadLibrary(String libname) This post will try to explain the differences of these two ways. According to Java Doc on System.load(), it has below description. Loads the native library specified by the filename argument. The filename a...

   NATIVE,JNI,JAVA,SYSTEM.LOAD,SYSTEM.LOADLIBRARY     2019-02-05 05:49:28

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