有谁知道如何使用Java以编程方式安装所有JVM(而不是默认的JVM)？
例如,用户的计算机上安装了2个JVM:
JDK 5
JDK 6
我需要知道安装的所有版本,以便切换它正在使用的版本(默认情况下),然后以编程方式调用javac以使用特定的JDK版本编译一些源代码.
我一直在寻找网上的一些信息,我发现:
但我找不到我想要的东西.
Pet*_*cio 13
我最近处理的情况非常相似.以下代码几乎完全符合您的需求.它搜索java JRE和JDK,而不仅仅是JDK,但应该很容易根据您的需要进行编辑.注意:仅限Windows
/**
* Java Finder by petrucio@stackoverflow(828681) is licensed under a Creative Commons Attribution 3.0 Unported License.
* Needs WinRegistry.java. Get it at: https://stackoverflow.com/questions/62289/read-write-to-windows-registry-using-java
*
* JavaFinder - Windows-specific classes to search for all installed versions of java on this system
* Author: petrucio@stackoverflow (828681)
*****************************************************************************/
import java.util.*;
import java.io.*;
/**
* Helper class to fetch the stdout and stderr outputs from started Runtime execs
* Modified from http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html?page=4
*****************************************************************************/
class RuntimeStreamer extends Thread {
InputStream is;
String lines;
RuntimeStreamer(InputStream is) {
this.is = is;
this.lines = "";
}
public String contents() {
return this.lines;
}
public void run() {
try {
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line = null;
while ( (line = br.readLine()) != null) {
this.lines += line + "\n";
}
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
/**
* Execute a command and wait for it to finish
* @return The resulting stdout and stderr outputs concatenated
****************************************************************************/
public static String execute(String[] cmdArray) {
try {
Runtime runtime = Runtime.getRuntime();
Process proc = runtime.exec(cmdArray);
RuntimeStreamer outputStreamer = new RuntimeStreamer(proc.getInputStream());
RuntimeStreamer errorStreamer = new RuntimeStreamer(proc.getErrorStream());
outputStreamer.start();
errorStreamer.start();
proc.waitFor();
return outputStreamer.contents() + errorStreamer.contents();
} catch (Throwable t) {
t.printStackTrace();
}
return null;
}
public static String execute(String cmd) {
String[] cmdArray = { cmd };
return RuntimeStreamer.execute(cmdArray);
}
}
/**
* Helper struct to hold information about one installed java version
****************************************************************************/
class JavaInfo {
public String path; //! Full path to java.exe executable file
public String version; //! Version string. "Unkown" if the java process returned non-standard version string
public boolean is64bits; //! true for 64-bit javas, false for 32
/**
* Calls 'javaPath -version' and parses the results
* @param javaPath: path to a java.exe executable
****************************************************************************/
public JavaInfo(String javaPath) {
String versionInfo = RuntimeStreamer.execute( new String[] { javaPath, "-version" } );
String[] tokens = versionInfo.split("\"");
if (tokens.length < 2) this.version = "Unkown";
else this.version = tokens[1];
this.is64bits = versionInfo.toUpperCase().contains("64-BIT");
this.path = javaPath;
}
/**
* @return Human-readable contents of this JavaInfo instance
****************************************************************************/
public String toString() {
return this.path + ":\n Version: " + this.version + "\n Bitness: " + (this.is64bits ? "64-bits" : "32-bits");
}
}
/**
* Windows-specific java versions finder
*****************************************************************************/
public class JavaFinder {
/**
* @return: A list of javaExec paths found under this registry key (rooted at HKEY_LOCAL_MACHINE)
* @param wow64 0 for standard registry access (32-bits for 32-bit app, 64-bits for 64-bits app)
* or WinRegistry.KEY_WOW64_32KEY to force access to 32-bit registry view,
* or WinRegistry.KEY_WOW64_64KEY to force access to 64-bit registry view
* @param previous: Insert all entries from this list at the beggining of the results
*************************************************************************/
private static List<String> searchRegistry(String key, int wow64, List<String> previous) {
List<String> result = previous;
try {
List<String> entries = WinRegistry.readStringSubKeys(WinRegistry.HKEY_LOCAL_MACHINE, key, wow64);
for (int i = 0; entries != null && i < entries.size(); i++) {
String val = WinRegistry.readString(WinRegistry.HKEY_LOCAL_MACHINE, key + "\\" + entries.get(i), "JavaHome", wow64);
if (!result.contains(val + "\\bin\\java.exe")) {
result.add(val + "\\bin\\java.exe");
}
}
} catch (Throwable t) {
t.printStackTrace();
}
return result;
}
/**
* @return: A list of JavaInfo with informations about all javas installed on this machine
* Searches and returns results in this order:
* HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment (32-bits view)
* HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment (64-bits view)
* HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Development Kit (32-bits view)
* HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Development Kit (64-bits view)
* WINDIR\system32
* WINDIR\SysWOW64
****************************************************************************/
public static List<JavaInfo> findJavas() {
List<String> javaExecs = new ArrayList<String>();
javaExecs = JavaFinder.searchRegistry("SOFTWARE\\JavaSoft\\Java Runtime Environment", WinRegistry.KEY_WOW64_32KEY, javaExecs);
javaExecs = JavaFinder.searchRegistry("SOFTWARE\\JavaSoft\\Java Runtime Environment", WinRegistry.KEY_WOW64_64KEY, javaExecs);
javaExecs = JavaFinder.searchRegistry("SOFTWARE\\JavaSoft\\Java Development Kit", WinRegistry.KEY_WOW64_32KEY, javaExecs);
javaExecs = JavaFinder.searchRegistry("SOFTWARE\\JavaSoft\\Java Development Kit", WinRegistry.KEY_WOW64_64KEY, javaExecs);
javaExecs.add(System.getenv("WINDIR") + "\\system32\\java.exe");
javaExecs.add(System.getenv("WINDIR") + "\\SysWOW64\\java.exe");
List<JavaInfo> result = new ArrayList<JavaInfo>();
for (String javaPath: javaExecs) {
if (!(new File(javaPath).exists())) continue;
result.add(new JavaInfo(javaPath));
}
return result;
}
/**
* @return: The path to a java.exe that has the same bitness as the OS
* (or null if no matching java is found)
****************************************************************************/
public static String getOSBitnessJava() {
String arch = System.getenv("PROCESSOR_ARCHITECTURE");
String wow64Arch = System.getenv("PROCESSOR_ARCHITEW6432");
boolean isOS64 = arch.endsWith("64") || (wow64Arch != null && wow64Arch.endsWith("64"));
List<JavaInfo> javas = JavaFinder.findJavas();
for (int i = 0; i < javas.size(); i++) {
if (javas.get(i).is64bits == isOS64) return javas.get(i).path;
}
return null;
}
/**
* Standalone testing - lists all Javas in the system
****************************************************************************/
public static void main(String [] args) {
List<JavaInfo> javas = JavaFinder.findJavas();
for (int i = 0; i < javas.size(); i++) {
System.out.println("\n" + javas.get(i));
}
}
}
您还需要更新的WinRegistry.java来从Windows注册表的32位和64位部分读取值:https://stackoverflow.com/a/11854901/828681
我通常不是一个java程序员,所以我的代码可能不遵循java约定.起诉我.
这是从我的Win 7 64位机器运行的示例:
>java JavaFinder
C:\Program Files (x86)\Java\jre6\bin\java.exe:
Version: 1.6.0_31
Bitness: 32-bits
C:\Program Files\Java\jre6\bin\java.exe:
Version: 1.6.0_31
Bitness: 64-bits
D:\Dev\Java\jdk1.6.0_31\bin\java.exe:
Version: 1.6.0_31
Bitness: 64-bits
C:\Windows\system32\java.exe:
Version: 1.6.0_31
Bitness: 64-bits
C:\Windows\SysWOW64\java.exe:
Version: 1.6.0_31
Bitness: 32-bits
安装是相当模糊的 - 即使 JRE 和 JDK 附带安装程序，实际上我们只需将 JRE 或 JDK 的文件复制到计算机上就可以立即使用它。
因此，一般来说，您必须在本地计算机上找到所有java或可执行文件，并调用以查看1，如果这个名为/ 的可执行文件确实是 JRE（的一部分）。java.exejava -versionjavajava.exe
刚刚看到，您要求JVM 并想要调用编译器。如果您正在寻找 JDK，请使用上述方法，但找到所有javac/ javac.exe。他们也有一个-version选择。
1这种方法没有风险 - 没有乐趣- 请仔细查看 Sean 的评论！如果您不能信任机器（或其用户），那么您可能需要测试可执行文件是脚本/批处理还是二进制文件 - 即使二进制文件也可以擦除您的磁盘，甚至原始的 javac 可执行文件也可以替换为一些邪恶的代码......
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