我试图创建从任何类型(比如Int)到String的隐式转换...
隐式转换为String意味着RichString方法(如反向)不可用.
implicit def intToString(i: Int) = String.valueOf(i)
100.toCharArray // => Array[Char] = Array(1, 0, 0)
100.reverse // => error: value reverse is not a member of Int
100.length // => 3
隐式转换为RichString意味着String方法(如toCharArray)不可用
implicit def intToRichString(i: Int) = new RichString(String.valueOf(i))
100.reverse // => "001"
100.toCharArray // => error: value toCharArray is not a member of Int
100.length // => 3
使用两个隐式转换意味着重复的方法(如长度)是不明确的.
implicit def intToString(i: Int) = String.valueOf(i)
implicit def intToRichString(i: Int) = new RichString(String.valueOf(i))
100.toCharArray // => Array[Char] = Array(1, …JMS API允许消息声明replyTo Destination实例.(即的超类Queue,Topic).然后,服务可以使用此队列向发送方发送回复消息.
Destination可以设置为ReplyTo值的限制是什么？这似乎不太可行,因为服务可能甚至没有任何到定义的网络路由Destination,因此无法返回任何消息.JMS是否以某种方式断言所提供的有效性(可达性)Destination？或者仅仅是服务尝试响应给定Destination并在必要时失败.
我在尝试使用Spring-test时没有成功地获得JDBC事务回滚.当我运行以下内容时,始终会提交SQL更新.
package my.dao.impl;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.annotation.Rollback;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.TestExecutionListeners;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.support.DependencyInjectionTestExecutionListener;
import org.springframework.test.context.transaction.TransactionConfiguration;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.Statement;
@RunWith(SpringJUnit4ClassRunner.class)
@TestExecutionListeners({DependencyInjectionTestExecutionListener.class})
@ContextConfiguration(locations={"classpath:ApplicationContext-test-DAOs.xml"})
@TransactionConfiguration(defaultRollback = true)
public class ConfirmationMatchingDAOImplTest {
@Autowired
private DataSource dataSource;
@Test
public void shouldInsertSomething() throws Exception {
final Connection connection = dataSource.getConnection();
final Statement statement = connection.createStatement();
statement.executeUpdate("insert into TEST_INSERT values (1, 'hello')");
statement.close();
connection.close();
}
}
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.microsoft.sqlserver.jdbc.SQLServerDriver"/>
<property name="url" value="jdbc:sqlserver://makeitfunky:1490;databaseName=fonzie"/>
<property name="username" value="ralph"/> …特定
val strings = Set("Hi", "there", "friend")
def numberOfCharsDiv2(s: String) = scala.util.Try {
if (s.length % 2 == 0) s.length / 2 else throw new RuntimeException("grr")
}
为什么我不能flatMap离开方法调用产生的Try？即
strings.flatMap(numberOfCharsDiv2)
<console>:10: error: type mismatch;
found : scala.util.Try[Int]
required: scala.collection.GenTraversableOnce[?]
strings.flatMap(numberOfCharsDiv2)
要么
for {
s <- strings
n <- numberOfCharsDiv2(s)
} yield n
<console>:12: error: type mismatch;
found : scala.util.Try[Int]
required: scala.collection.GenTraversableOnce[?]
n <- numberOfCharsDiv2(s)
但是,如果我使用Option而不是Try,则没有问题.
def numberOfCharsDiv2(s: String) = if (s.length % 2 == 0)
Some(s.length / 2) else None
strings.flatMap(numberOfCharsDiv2) …如何在序列化之前将转换应用于字段？
例如,如何确保字段lat和lon此结构定义在序列化之前舍入到最多6个小数位？
#[derive(Debug, Serialize)]
struct NodeLocation {
#[serde(rename = "nodeId")]
id: u32,
lat: f32,
lon: f32,
}
能否帮助我如何使用一个公共连接表连接三个表？我有USER,APPLICATION和ROLE表.我希望将他们的ID加入名为USER_APP_ROLE(user.ID,application.ID,role.ID)的表中.
当我删除Join Many to Many中的Application或Role表时,我的代码正在运行.
我做了以下代码:
User.java
@ManyToMany (targetEntity=Role.class)
@JoinTable(name="USER_APPLICATION_ROLE",
joinColumns=@JoinColumn(name="USER_ID"),
inverseJoinColumns=@JoinColumn(name="ROLE_ID"))
private Collection<Role> roles;
@ManyToMany (targetEntity=Application.class)
@JoinTable(name="USER_APPLICATION_ROLE",
joinColumns=@JoinColumn(name="USER_ID"),
inverseJoinColumns=@JoinColumn(name="APPLICATION_ID"))
private Collection<Application> applications;
Role.java
@ManyToMany(mappedBy="roles", targetEntity=User.class)
private Collection<User> users = new ArrayList<User>();
Application.java
@ManyToMany(mappedBy="applications", targetEntity=User.class)
private Collection<User> users = new ArrayList<User>();
当我尝试运行以下测试时:
user.getRoles().add(role1);
user.getRoles().add(role2);
role1.getUsers().add(user);
role1.getUsers().add(user);
role2.getUsers().add(user);
role2.getUsers().add(user);
user.getApplications().add(app1);
user.getApplications().add(app2);
app1.getUsers().add(user);
app2.getUsers().add(user);
......
session.beginTransaction();
session.save(user);
session.save(role1);
session.save(role2);
session.save(app1);
session.save(app2);
我收到以下错误:
Hibernate: select seq_cm_user.nextval from dual
Hibernate: select seq_role.nextval from dual
Hibernate: select seq_role.nextval from dual
Hibernate: select seq_application.nextval from dual …目标:列出所有罐子中的文件.
这有效:
for f in `find . -name "*.jar"`; do jar tvf $f; done
这也有效:
find . -name "*.jar" -exec jar tvf {} \;
这不(它不打印任何输出):
find . -name "*.jar" | xargs jar tvf
为什么后者不起作用？
是否可以自动化Spray应用程序中的路径文档？
例如,是否有一个SBT插件可以生成降价描述它对喷雾路线的了解？