使用hibernate框架制作学生信息查询(多表查询)

来源：互联网发布：全球雾霾数据统计编辑：程序博客网时间：2024/06/14 04:04

需求：通过学院表和学生表进行关联，从浏览器点击学院信息，显示出各学院学生信息

功能展示：

这里写图片描述

代码演示：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head></head><body>    <h2>学院信息</h2>    <table>        <c:forEach items="${list}" var="dept">            <tr>                <td><a target="frm"                    href="<c:url value='/DemoServlet?cmd=queryStudents&id=${dept.id}'/>"                    class="type"> ${dept.name} </a></td>            </tr>        </c:forEach>    </table>    <br />    <a href="<c:url value='/DemoServlet?cmd=addDept'/>">添加部门</a>    <br />    <iframe name="frm"        style="display:block;width:50%;height:100%;border-width:0px">    </iframe></body></html>

我们通过隐藏帧来显示搜索后的学生信息：qlist.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%><head><style type="text/css">table {    border: 1px solid gray;    border-collapse: collapse;    width: 60%;}td {    border: 1px solid gray;    padding: 5px;}</style></head><h2>查询结果</h2><table>    <tr style="background:#7D7DFF;">        <td>学号</td>        <td>姓名</td>        <td>年龄</td>        <td>学员名称</td>        <td>操作</td>    </tr>    <c:forEach items="${students}" var="stud">        <tr>            <td>${stud.studId }</td>            <td>${stud.studName }</td>            <td>${stud.age }</td>            <td>${stud.dept.name }</td>            <td><a                href="<c:url value='/DemoServlet?cmd=delStudent&studId=${stud.studId }' />">删除</a>            </td>        </tr>    </c:forEach></table>

我们需要先来配置hiberbate所需的文件： Student.hbm.xml:通过Student中配置`<many-to-one>`来匹配学生和学院，而在Dept中通过`<set>` 来配置学院和学生的一对多关系，我们需要将set中的inverse设为true，这个参数能够将两对象设成级联，这样，就可以通过查询学生后自动索引出学院信息

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="cn.hncu.demo.domain">    <class name="Student" table="students" catalog="hib">        <!-- id标记是指Student类中的属性变量,该属性是对应表主键字段的 -->        <id name="studId" type="java.lang.String">            <!-- column标记是指数据库表中的哪一列(字段) -->            <column name="id" length="8"></column>        </id>        <!-- 其他字段都用property 只有主键用id -->        <property name="studName" type="java.lang.String">            <column name="name" length="40"></column>        </property>        <property name="age" type="java.lang.Integer">            <column name="age"></column>        </property>        <many-to-one name="dept" class="Dept" fetch="select">            <column name="deptId" length="8"></column>        </many-to-one>    </class>    <class name="Dept" table="depts" catalog="hib">        <id name="id" type="java.lang.String">            <column name="id" length="8"></column>            <generator class="assigned"></generator>        </id>        <property name="name" type="java.lang.String">            <column name="name" length="40"></column>        </property>        <set name="student" table="students" inverse="true" cascade="all">            <key>                <column name="deptId"></column><!-- 配置外键字段 -->            </key>            <one-to-many class="Student"/>        </set>    </class></hibernate-mapping>

我这里将Servlet整合通过继承BaseServlet通过子对象的方法名称加载方法，再来调用： Baseserlvet：

package cn.hncu.utils;import java.io.IOException;import java.io.UnsupportedEncodingException;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.util.Iterator;import java.util.Map;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletRequestWrapper;import javax.servlet.http.HttpServletResponse;import org.apache.log4j.Logger;/** * 基类， 1:修改HttpServletRequest增强 2:动态调用用户指定的方法?cmd=save....,默认为execute方法 *  * @author <a href="mailto:jack@hncu.cn">杰克</a> * @version 1.0 2014-12-29 */public abstract class BaseServlet extends HttpServlet {    private Logger log = Logger.getLogger(BaseServlet.class);    private static final long serialVersionUID = 1L;    @Override    public void doGet(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {        doPost(req, resp);    }    @Override    public void doPost(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {        req.setCharacterEncoding("utf-8");        String cmd = req.getParameter("cmd");        if (null == cmd || cmd.trim().equals("")) {            cmd = "execute";        }        log.debug("调用的方法为:" + cmd);        try {            Method method = this.getClass().getMethod(cmd,                    HttpServletRequest.class, HttpServletResponse.class);            method.invoke(this, req, resp);        } catch (NoSuchMethodException e) {            throw new RuntimeException("没有此方法：" + e.getMessage(), e);        } catch (InvocationTargetException e) {            throw new RuntimeException("目标方法执行失败：" + e.getMessage(), e);        } catch (IllegalAccessException e) {            throw new RuntimeException("你可能访问了一个私有的方法：" + e.getMessage(), e);        } catch (Exception e) {            throw new RuntimeException(e.getMessage(), e);        }    }    public abstract void execute(HttpServletRequest req,            HttpServletResponse resp) throws Exception;}

DemoServlet：

package cn.hncu.demo;import java.io.IOException;import java.io.PrintWriter;import java.util.HashSet;import java.util.Iterator;import java.util.List;import java.util.Set;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import cn.hncu.demo.domain.Dept;import cn.hncu.demo.domain.Student;import cn.hncu.demo.service.DemoServiceImpl;import cn.hncu.utils.BaseServlet;public class DemoServlet extends BaseServlet {    private DemoServiceImpl service = new DemoServiceImpl();    @Override    public void execute(HttpServletRequest req, HttpServletResponse resp)            throws Exception {        List<Dept> list = service.queryAllStudent();        req.getSession().setAttribute("list", list);        String showPage = getInitParameter("show");        resp.sendRedirect(getServletContext().getContextPath() + showPage);    }    public void addDept(HttpServletRequest req, HttpServletResponse resp)            throws Exception {        Dept dept = new Dept();        dept.setId("D004");        dept.setName("创新学院");        Student stud1 = new Student();        stud1.setstudId("s101");        stud1.setstudName("贾宝玉");        stud1.setAge(20);        stud1.setDept(dept);        dept.getStudent().add(stud1);        Student stud2 = new Student();        stud2.setstudId("s102");        stud2.setstudName("林黛玉");        stud2.setAge(20);        stud2.setDept(dept);        dept.getStudent().add(stud2);        Student stud3 = new Student();        stud3.setstudId("s103");        stud3.setstudName("林玉");        stud3.setAge(20);        stud3.setDept(dept);        dept.getStudent().add(stud3);        service.addDept(dept);        resp.sendRedirect(getServletContext().getContextPath() + "/index.jsp");    }    public void queryStudents(HttpServletRequest req, HttpServletResponse resp)            throws Exception {        String id = req.getParameter("id");        Dept d = new Dept();        d.setId(id);        List<Dept> list = service.queryDept(d);        d = list.get(0);        Set<Student> s = d.getStudent();        req.getSession().setAttribute("students", s);        req.getRequestDispatcher("/jsps/qlist.jsp").forward(req, resp);    }}

DaoJdbc：

package cn.hncu.demo.dao;import java.util.List;import org.hibernate.Query;import org.hibernate.Session;import org.hibernate.Transaction;import cn.hncu.demo.domain.Dept;import cn.hncu.demo.domain.Student;import cn.hncu.utils.HibernateUtil;public class DemoDaoJdbc {    public List<Dept> queryAllStudents() {        Session session = HibernateUtil.getSession();        Query q = session.createQuery("from Dept");// HQL                                                    // =                                                    // SQL中的关键字+                                                    // Java(类名，属性名)        List<Dept> list = q.list();        return list;    }    public void delStudent(Student stud) {        // Hibernate每次操作时重新获取session        Session session = HibernateUtil.getSession();        Transaction tran = session.beginTransaction();        session.delete(stud);        tran.commit();        session.clear();// 每个session中有一级缓存，在删除后可能没有及时删除缓存中的数据    }    public List<Dept> queryDept(Dept dept) {        boolean f1 = false, f2 = false, f3 = false;        Session session = HibernateUtil.getSession();        String hql = "from Dept d where 1=1";        if (dept.getId() != null && dept.getId().trim().length() > 0) {            hql = hql + " and d.id=:id";            f1 = true;        }        if (dept.getName() != null && dept.getName().trim().length() > 0) {            hql = hql + " and d.name like :name";            f2 = true;        }        Query q = session.createQuery(hql);        if (f1) {            q.setParameter("id", dept.getId());        }        if (f2) {            q.setParameter("name", "%" + dept.getName() + "%");        }        session.clear();        return q.list();    }    public void addDept(Dept dept) {        Session session = HibernateUtil.getSession();        Transaction tran =session.beginTransaction();        session.saveOrUpdate(dept);        tran.commit();        session.clear();    }}

这样我们就可以通过学院表和学生表进行关联，从浏览器点击学院信息，显示出各学院学生信息了

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