小编bha*_*ran的帖子

为什么默认构造函数在父类中是必需的(显式),如果它有一个有争议的构造函数

class A {    
  A(int i){    
  }
}

class B extends A {
}

class Main {    
  public static void main(String a[]){
    B b_obj = new B();
  }
}

这将是一个错误.

struts.xml和struts-config.xml有什么区别？它们是相同的还是它们之间有什么区别？

Mapper.xml(Mapper xml文件)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="TestDAO">
<insert id="insertEmployeeList" parameterType="java.util.List">
INSERT INTO EMPLOYEE (id, name) VALUES
<foreach collection="list" item="element" index="index" open="(" separator=","  close=")">
#{element.id}, #{element.name}
</foreach>
</insert>
</mapper>

Employee.java

public class Employee {
  private List<Emp> list = new ArrayList<Emp>();
  public List<Emp> getList() {
    return list;
  }
  public void setList(List<Emp> list) {
    this.list = list;
  }
}

Emp.java

public class Emp {
  public Emp(int id, String name) {
    this.id = id;
    this.name = name; …

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:jaxws="http://cxf.apache.org/jaxws" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://cxf.apache.org/jaxws http://cxf.apache.org/schemas/jaxws.xsd">
<import resource="classpath:META-INF/cxf/cxf.xml" />
<import resource="classpath:META-INF/cxf/cxf-extension-soap.xml" />
<import resource="classpath:META-INF/cxf/cxf-servlet.xml" />
<jaxws:endpoint xmlns:tns="http://sampleService.viasat.com/"
id="sampleserviceinterfcae" implementor="com.viasat.sampleservice.SampleServiceInterfcaeImpl"
    wsdlLocation="wsdl/sampleserviceimplementation.wsdl" endpointName="tns:SampleServiceImplementationPort"
    serviceName="tns:SampleServiceImplementationService" address="/SampleServiceImplementationPort">
<jaxws:features>
<bean class="org.apache.cxf.feature.LoggingFeature" />
</jaxws:features>
</jaxws:endpoint>
</beans>

我正在使用Maven来构建应用程序.在mvn clean和mvn install之后,我在Tomcat中部署应用程序,之后我收到以下错误'来自ServletContext资源[/WEB-INF/classes/cxf-beans.xml]的XML文档中的第11行无效; 嵌套异常是org.xml.sax.SAXParseException:cvc-complex-type.2.4.c:匹配的通配符是strict,但是找不到元素'jaxws:endpoint'的声明.

我已经在Mybatis中完成了批量插入，并且工作正常。但是我不确定如何在bean类中为每一行存储生成的主键。这是我的代码，

Mapper.xml

    <?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="com.xxxx.sample.test.dao.TestDAO">
        <insert id="insertEmployeeList" parameterType="java.util.List">
            INSERT ALL
            <foreach collection="list" item="element" index="index">
                INTO EMPLOYEE (name) values (#{element.name})
            </foreach>
            SELECT * FROM dual
        </insert>
    </mapper>

Emp.java

public class Emp {
public Emp(int id, String name) {
this.id = id;
this.name = name;
}
private int id;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return …

为什么默认构造函数(同一个类)在调用默认构造函数时没有调用,但父类的默认构造函数被调用 - 为什么？

class A{
    A(){
        System.out.println("A()");
    }
}

class B extends A{
    B(){
        System.out.println("B()");
    }
}

class C extends B{
    C(){
        System.out.println("C()");
    }
    C(int i){
        System.out.println("<------>"+i);
    }
}
public class sample {
    public static void main(String[] args) {
        C c = new C(8);

    }
}

输出:

A()
B()
<------>8

如果两个对象相等,那么它们应该具有相同的hascode但反之则不正确(即如果两个对象具有相同的哈希码并不意味着它们是相等的) - 你能用一个例子证明它是正确的吗？谢谢