System.getProperty方法

2022-09-01 01:30:19 阅读：201 来源： 互联网

标签：Java java specification System vendor version key getProperty 方法

Demo

private static String zookeeperHost = System.getProperty("zookeeper.address", "127.0.0.1");
private static String zookeeperPort = System.getProperty("zookeeper.port", "2181");

使用System.getProperty获得属性，如果未获得指定key的值，使用后面的作为default value。

System.getProperty方法支持以下属性：

java.version：Java Runtime Environment version, which may be interpreted as a Runtime.Version
java.version.date：Java Runtime Environment version date, in ISO-8601 YYYY-MM-DD format, which may be interpreted as a java.time.LocalDate
java.vendor：Java Runtime Environment vendor
java.vendor.url：Java vendor URL
java.vendor.version：Java vendor version
java.home：Java installation directory
java.vm.specification.version：Java Virtual Machine specification version, whose value is the feature element of the runtime version
java.vm.specification.vendor：Java Virtual Machine specification vendor
java.vm.specification.name：Java Virtual Machine specification name
java.vm.version：Java Virtual Machine implementation version which may be interpreted as a Runtime.Version
java.vm.vendor：Java Virtual Machine implementation vendor
java.vm.name：Java Virtual Machine implementation name
java.specification.version：Java Runtime Environment specification version, whose value is the feature element of the runtime version
java.specification.vendor：Java Runtime Environment specification vendor
java.specification.name：Java Runtime Environment specification name
java.class.version：Java class format version number
java.class.path：Java class path (refer to ClassLoader.getSystemClassLoader() for details)
java.library.path：List of paths to search when loading libraries
java.io.tmpdir：Default temp file path
java.compiler：Name of JIT compiler to use
os.name：Operating system name
os.arch：Operating system architecture
os.version：Operating system version
file.separator：File separator ("/" on UNIX)
path.separator：Path separator (":" on UNIX)
line.separator：Line separator ("\n" on UNIX)
user.name：User's account name
user.home：User's home directory
user.dir：User's current working directory

    public static String getProperty(String key) {
        checkKey(key);
        SecurityManager sm = getSecurityManager();
        if (sm != null) {
            sm.checkPropertyAccess(key);
        }

        return props.getProperty(key);
    }

checkKey(String key)

private static void checkKey(String key) {
        if (key == null) {
            throw new NullPointerException("key can't be null");
        }
        if (key.equals("")) {
            throw new IllegalArgumentException("key can't be empty");
        }
    }

props.getProperty(key)

    public String getProperty(String key) {
        Object oval = map.get(key);
        String sval = (oval instanceof String) ? (String)oval : null;
        Properties defaults;
        return ((sval == null) && ((defaults = this.defaults) != null)) ? defaults.getProperty(key) : sval;
    }

标签：Java,java,specification,System,vendor,version,key,getProperty,方法
来源： https://www.cnblogs.com/use-D/p/16645121.html

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System.getProperty方法

Demo