A brief discussion on how Java reads and writes registry

This article mainly studies the two ways of reading and writing registry in Java Preferences and jRegistry. The details are as follows.

Since the java program is "write once, run everywhere", and using java to read and write the registry, the cross-platform nature of the program is poor. Java's operation of the registry is impossible in versions before jdk1.4, and can only be implemented with JNI; however, the prefs package provided after jdk1.4 can operate the Windows registry, but root is only under SOFTWARE/JavaSoft/prefs. It is probably because of this dilemma, and it is necessary to ensure that the so-called platform is irrelevant and take care of everyone's dependence on Windows. The following will introduce the operation of the registry from two aspects.

1. Use the Preferences class provided by JDK

First, get an object of Preferences, which specifies where you want to write information in the registry, that is, the node. Then use put(String key,String value) or putInt(), tDouble(), etc. to assign values ​​to the relevant items. Here is the demo program.

 import java.util.prefs.*; public class Registery { String[] keys = {"version", "initial", "creator"}; String[] values ​​= {"1.3", "ini.mp3", "[email protected]"}; //Save the corresponding value in a variable and go to public void writeValue() { // Write the registry value under HKEY_LOCAL_MACHINE/Software/JavaSoft/prefs. Preferences pre = Preferences.systemRoot().node("/javaplayer"); for (int i = 0; i < keys.length; i++) { pre.put(keys, values); } } public static void main(String[] args) { Registery reg = new Registery(); reg.writeValue(); } }

Execute the above code and write the relevant value under the HKEY_LOCAL_MACHINE/Software/JavaSoft/prefs/javaplayer in the registry.

Finally, let me explain a few points:

• Don't capitalize the initial letter of your node, otherwise you will add a "/" before the entry in the registry;
• Values ​​in the registry can also be imported into an XML file. See the relevant documentation for details.
• If you replace Preferences pre = Preferences.systemRoot().node("/javaplayer"); in the code with Preferences pre = Preferences.userRoot().node("/javaplayer"); then the corresponding HKEY_LOCAL_MACHINE becomes HKEY_LOCAL_USER.
  

2. Use jRegistry to operate the registry

jRegistry uses JNI to encapsulate the WINDOWS registry API, which facilitates Java developers to access the Windows registry. First, let’s introduce jRegistryKey.jar and jRegistryKey.dll. These two files are necessary to use jRegistry to operate the registry: one is the jar package, which is a file that includes the java class; the other is a dynamic link library file, which provides the local code required to access the registry (i.e., C/C++).

The following is a detailed introduction to the usage process:

• Add jRegistryKey.jar in JBuilder's menu Project->Project Properties->Required Libraries or add the jar file in the environment variable classpath;
• Place jRegistryKey.dll in the current directory of the project;
• Import the statement in the access registry class: import ca.beq.util.win32.registry.*; there are two classes in the package: RegistryKey and RegistryValue. Where RegistryKey is the Java representation of the registry key, it provides the creat() and delete() methods to create and delete keys, enumerate subkeys and values, set and get key values, etc.; RegistryValue is the Java? representation of a registry value (defined as a name, a type, and data).

Implement code

• Create a new key:

 RegistryKey r = new RegistryKey(RootKey.HKEY_CURRENT_USER, "Software//BEQ Technologies"); r.create();

• Create a subkey:

 RegistryKey r = new RegistryKey(RootKey.HKEY_CURRENT_USER, "Software"); r.createSubkey("BEQ Technologies");

• Delete an existing key value:

 try { RegistryKey r = new RegistryKey(RootKey.HKEY_CURRENT_USER, "Software//BEQ Technologies"); r.delete(); } // try catch(RegistryException re) { re.printStackTrace(); } // catch

• Enumeration subkey:

 RegistryKey r = new RegistryKey(RootKey.HKEY_CURRENT_USER, "Software"); if(r.hasSubkeys()) { Iterator i = r.subkeys(); while(i.hasNext()) { RegistryKey x = (RegistryKey)i.next(); System.out.println(x.toString()); } // while } // if

• Read the value of the key in the registry:

 RegistryKey r = new RegistryKey(RootKey.HKEY_CURRENT_USER, "Software//BEQ Technologies"); if(r.hasValue("myValue")) { RegistryValue v = r.getValue("myValue"); System.out.println(v.toString());// } // if

Note: v.toString() is only the key value corresponding to the key myValue. To get the value data corresponding to the myValue key, you need String str = v.getDate().toSting();

• Set the value of the key in the registry:

 RegistryKey r = new RegistryKey(RootKey.HKEY_CURRENT_USER, "Software//BEQ Technologies"); RegistryValue v = new RegistryValue("myVal", ValueType.REG_SZ, "data"); r.setValue(v);

• Enumerate all values ​​of a key:

 RegistryKey r = new RegistryKey(RootKey.HKEY_CURRENT_USER, "Software"); if(r.hasValues()) { Iterator i = r.values(); while(i.hasNext()) { RegistryValue v = (RegistryValue)i.next(); System.out.println(v.toString()); } // while } // if

The following is a demo program for reference only.

 // create a new key, "Test", under HKLM RegistryKey r = new RegistryKey(RootKey.HKEY_LOCAL_MACHINE, "Test"); if(!r.exists()) { r.create(); } // if // create value entries RegistryValue v = new RegistryValue("aString", ValueType.REG_SZ, "test"); r.setValue(v); v.setName("aDword"); v.setType(ValueType.REG_DWORD); v.setData(new Integer(0x1001001)); r.setValue(v); // read value entries Iterator i = r.values(); while(i.hasNext()) { v = (RegistryValue)i.next(); System.out.println(v.toString()); } // while // delete registry key r.delete();

Summarize

The above is the entire content of this article about briefly discussing the ways of reading and writing registry in Java Preferences and jRegistry. I hope it will be helpful to everyone. Interested friends can continue to refer to other related topics on this site. If there are any shortcomings, please leave a message to point it out. Thank you friends for your support for this site!