Properties

package resource.and.property;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;
import java.util.Properties;

public class Main {
    public static final String THIS_PATH = Main.class.getResource("").getPath();
    public static final String CONFIG_FILE = THIS_PATH + "app.properties";
    public static final InputStream INPUT = Main.class
            .getResourceAsStream("app.properties");

    public static void main(String[] args) {
        // getJVMProperties();
        getProperties();
    }


    public static void getJVMProperties() {
        Properties props = System.getProperties();
        props.list(System.out);
    }

    public static void getProperties() {
        Properties pps = new Properties();
        try {
            pps.load(new FileInputStream(CONFIG_FILE));
            // pps.load(INPUT);
        } catch (IOException e) {
            e.printStackTrace();
        }
        @SuppressWarnings("rawtypes")
        Enumeration enum1 = pps.propertyNames();
        while (enum1.hasMoreElements()) {
            String strKey = (String) enum1.nextElement();
            String strValue = pps.getProperty(strKey);
            System.out.println(strKey + "=" + strValue);
        }
    }

    static class TestProperties {
        public static String GetValueByKey(String filePath, String key) {
            Properties pps = new Properties();
            try {
                InputStream in = new BufferedInputStream(new FileInputStream(
                        filePath));
                pps.load(in);
                String value = pps.getProperty(key);
                System.out.println(key + " = " + value);
                return value;

            } catch (IOException e) {
                e.printStackTrace();
                return null;
            }
        }

        @SuppressWarnings("rawtypes")
        public static void GetAllProperties(String filePath) throws IOException {
            Properties pps = new Properties();
            InputStream in = new BufferedInputStream(new FileInputStream(
                    filePath));
            pps.load(in);
            Enumeration en = pps.propertyNames();

            while (en.hasMoreElements()) {
                String strKey = (String) en.nextElement();
                String strValue = pps.getProperty(strKey);
                System.out.println(strKey + "=" + strValue);
            }

        }

        public static void WriteProperties(String filePath, String pKey,
                String pValue) throws IOException {
            Properties pps = new Properties();
            InputStream in = new FileInputStream(filePath);
            pps.load(in);
            OutputStream out = new FileOutputStream(filePath);
            pps.setProperty(pKey, pValue);
            pps.store(out, "Update " + pKey + " name");
        }

        public static void main(String[] args) throws IOException {
            String value = GetValueByKey(CONFIG_FILE, "name");
            System.out.println(value);
            System.out.println("--------------");
            GetAllProperties(CONFIG_FILE);
            System.out.println("--------------");
            WriteProperties(CONFIG_FILE, "long", "212");
            GetAllProperties(CONFIG_FILE);
        }
    }
}

一般两种方式获得properties：

pps.load(new BufferedInputStream(new FileInputStream(filePath)));


pps.load(Main.class.getResourceAsStream(filePath));

注意：上述代码中各种stream流都未关闭，在实际应用中记得关闭流。