在Java Jersey RESTful Web应用程序中加载属性文件,以在整个应用程序中保留？

Question

我目前正在使用Jersey构建RESTful API.到目前为止,一切进展顺利,但是,所有配置条目都已经过硬编码.(即数据库主机,数据库用户名等).

我希望能够设置config.properties我的WEB-INF文件夹中存在的文件,以包含所有这些配置规范.

我担心如果我在Classpath上读取文件的"经典"方式,我会为每个请求执行文件I/O. 我希望能够在启动时读取一次(我知道这涉及到ServletListener我的web.xml文件中.

这是我在下面的内容:

web.xml:

<listener>
    <listener-class>com._1834Software.Config</listener-class>
</listener>

我想做类似这样的事情(我在StackOverflow上找到了这个),但我认为它不一定适用于Jersey:

Config.java

public class Config implements ServletContextListener {
    private static final String ATTRIBUTE_NAME = "config";
    private Properties config = new Properties();

    @Override
    public void contextInitialized(ServletContextEvent event) {
        try {

            config.load(Thread.currentThread().getContextClassLoader().getResourceAsStream("config.properties"));

        } catch (IOException err) {
            err.printStackTrace();
        }

        event.getServletContext().setAttribute(ATTRIBUTE_NAME, this);

    }

    @Override
    public void contextDestroyed(ServletContextEvent event) { /**/ }

    public static Config getInstance(ServletContext context) {
        return (Config) context.getAttribute(ATTRIBUTE_NAME);
    }

    public String getProperty(String key) {
        return config.getProperty(key);
    }

}

我试着像这样称呼它:

Config config = Config.getInstance(getServletContext());
String property = config.getProperty("HEROKU_DATABASE_URL");

但是我收到以下错误:

Error:(32, 40) java: cannot find symbol
symbol:   method getServletContext()
location: class com._1834Software.database.DatabaseHandler

这是文件(DatabaseHandler.java我试图称之为):

public class DatabaseHandler {
    public Connection connection = null;

    Config config = Config.getInstance(getServletContext());
    String property = config.getProperty("somekey");


    /* Database Parameters */
    private String DRIVER = "org.postgresql.Driver";
    private String host = "XXXXX";
    private String userName = "XXXXX";
    private String password = "XXXXX";

    public void connect() throws SQLException {
        try {

            Class.forName(DRIVER);

        } catch (ClassNotFoundException err) {

            err.printStackTrace();   

        }

        try {

            connection = DriverManager.getConnection(host, userName, password);

        } catch (SQLException err) {
            err.printStackTrace();
        }
    }

    public void disconnect() throws SQLException { connection.close(); }
}

Answer 1

加载属性文件的方法有很多种.为避免在您的项目中引入任何新依赖项,以下是一些可能对您有帮助的代码段.这只是一种方法......

1. 定义属性文件.我把它放在src/main/resources /中作为"config.properties"

   sample.property=i am a sample property
   

2. 在您的jersey配置文件中(假设您正在使用类扩展Application),您可以在那里加载属性文件,它只会在应用程序初始化期间加载一次,以避免您一遍又一遍地执行文件I/O:

   import java.io.IOException;
   import java.io.InputStream;
   import java.util.HashSet;
   import java.util.Properties;
   import java.util.Set;
   
   import javax.ws.rs.ApplicationPath;
   import javax.ws.rs.core.Application;
   
   @ApplicationPath("sample")
   public class JerseyConfig extends Application {
   
   public static final String PROPERTIES_FILE = "config.properties";
   public static Properties properties = new Properties();
   
   private Properties readProperties() {
       InputStream inputStream = getClass().getClassLoader().getResourceAsStream(PROPERTIES_FILE);
       if (inputStream != null) {
           try {
               properties.load(inputStream);
           } catch (IOException e) {
               // TODO Add your custom fail-over code here
               e.printStackTrace();
           }
       }
       return properties;
   }
   
   @Override
   public Set<Class<?>> getClasses() {     
       // Read the properties file
       readProperties();
   
       // Set up your Jersey resources
       Set<Class<?>> rootResources = new HashSet<Class<?>>();
       rootResources.add(JerseySample.class);
       return rootResources;
   }
   
   }
   

3. 然后,您可以在端点中引用您的属性,如下所示:

   import javax.ws.rs.GET;
   import javax.ws.rs.Path;
   import javax.ws.rs.Produces;
   import javax.ws.rs.core.MediaType;
   
   @Path("/")
   public class JerseySample {
   
       @GET
       @Path("hello")
       @Produces(MediaType.TEXT_PLAIN)
       public String get() {
           return "Property value is: " + JerseyConfig.properties.getProperty("sample.property");
       }
   
   }