Spring MVC CRUD用法示例图解

本文概述

• 建立表格
• Spring MVC CRUD示例

CRUD(创建, 读取, 更新和删除)应用程序是用于创建任何项目的最重要的应用程序。它提供了开发大型项目的想法。在Spring MVC中, 我们可以开发一个简单的CRUD应用程序。

在这里, 我们使用JdbcTemplate进行数据库交互。

建立表格

在这里, 我们正在使用MySQL数据库中存在的emp99表。它有4个字段：ID, 姓名, 薪水和名称。在此, id由序列自动生成。

Spring MVC CRUD示例

1.将依赖项添加到pom.xml文件。

pom.xml

<!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webmvc</artifactId>
    <version>5.1.1.RELEASE</version>
</dependency>

<!-- https://mvnrepository.com/artifact/org.apache.tomcat/tomcat-jasper -->
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat-jasper</artifactId>
    <version>9.0.12</version>
</dependency>
    <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
<dependency>  
    <groupId>javax.servlet</groupId>  
    <artifactId>servlet-api</artifactId>  
    <version>3.0-alpha-1</version>  
</dependency>
<!-- https://mvnrepository.com/artifact/javax.servlet/jstl -->
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>jstl</artifactId>
    <version>1.2</version>
</dependency>
    <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.11</version>
</dependency>
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-jdbc</artifactId>
    <version>5.1.1.RELEASE</version>
</dependency>

2.创建bean类

在这里, bean类包含与数据库中存在的字段相对应的变量(以及setter和getter方法)。

Emp.java

package com.srcmini.beans;  
  
public class Emp {  
private int id;  
private String name;  
private float salary;  
private String designation;  
  
public int getId() {  
    return id;  
}  
public void setId(int id) {  
    this.id = id;  
}  
public String getName() {  
    return name;  
}  
public void setName(String name) {  
    this.name = name;  
}  
public float getSalary() {  
    return salary;  
}  
public void setSalary(float salary) {  
    this.salary = salary;  
}  
public String getDesignation() {  
    return designation;  
}  
public void setDesignation(String designation) {  
    this.designation = designation;  
}  
  
}

3.创建控制器类

EmpController.java

package com.srcmini.controllers;   
import java.util.List;  
import org.springframework.beans.factory.annotation.Autowired;  
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ModelAttribute;  
import org.springframework.web.bind.annotation.PathVariable;  
import org.springframework.web.bind.annotation.RequestMapping;  
import org.springframework.web.bind.annotation.RequestMethod;   
import com.srcmini.beans.Emp;  
import com.srcmini.dao.EmpDao;  
@Controller  
public class EmpController {  
    @Autowired  
    EmpDao dao;//will inject dao from XML file  
      
    /*It displays a form to input data, here "command" is a reserved request attribute 
     *which is used to display object data into form 
     */  
    @RequestMapping("/empform")  
    public String showform(Model m){  
    	m.addAttribute("command", new Emp());
    	return "empform"; 
    }  
    /*It saves object into database. The @ModelAttribute puts request data 
     *  into model object. You need to mention RequestMethod.POST method  
     *  because default request is GET*/  
    @RequestMapping(value="/save", method = RequestMethod.POST)  
    public String save(@ModelAttribute("emp") Emp emp){  
        dao.save(emp);  
        return "redirect:/viewemp";//will redirect to viewemp request mapping  
    }  
    /* It provides list of employees in model object */  
    @RequestMapping("/viewemp")  
    public String viewemp(Model m){  
        List<Emp> list=dao.getEmployees();  
        m.addAttribute("list", list);
        return "viewemp";  
    }  
    /* It displays object data into form for the given id.  
     * The @PathVariable puts URL data into variable.*/  
    @RequestMapping(value="/editemp/{id}")  
    public String edit(@PathVariable int id, Model m){  
        Emp emp=dao.getEmpById(id);  
        m.addAttribute("command", emp);
        return "empeditform";  
    }  
    /* It updates model object. */  
    @RequestMapping(value="/editsave", method = RequestMethod.POST)  
    public String editsave(@ModelAttribute("emp") Emp emp){  
        dao.update(emp);  
        return "redirect:/viewemp";  
    }  
    /* It deletes record for the given id in URL and redirects to /viewemp */  
    @RequestMapping(value="/deleteemp/{id}", method = RequestMethod.GET)  
    public String delete(@PathVariable int id){  
        dao.delete(id);  
        return "redirect:/viewemp";  
    }   
}

4.创建DAO类

让我们创建一个DAO类来访问数据库中所需的数据。

EmpDao.java

package com.srcmini.dao;  
import java.sql.ResultSet;  
import java.sql.SQLException;  
import java.util.List;  
import org.springframework.jdbc.core.BeanPropertyRowMapper;  
import org.springframework.jdbc.core.JdbcTemplate;  
import org.springframework.jdbc.core.RowMapper;  
import com.srcmini.beans.Emp;  
  
public class EmpDao {  
JdbcTemplate template;  
  
public void setTemplate(JdbcTemplate template) {  
    this.template = template;  
}  
public int save(Emp p){  
    String sql="insert into Emp99(name, salary, designation) values('"+p.getName()+"', "+p.getSalary()+", '"+p.getDesignation()+"')";  
    return template.update(sql);  
}  
public int update(Emp p){  
    String sql="update Emp99 set name='"+p.getName()+"', salary="+p.getSalary()+", designation='"+p.getDesignation()+"' where id="+p.getId()+"";  
    return template.update(sql);  
}  
public int delete(int id){  
    String sql="delete from Emp99 where id="+id+"";  
    return template.update(sql);  
}  
public Emp getEmpById(int id){  
    String sql="select * from Emp99 where id=?";  
    return template.queryForObject(sql, new Object[]{id}, new BeanPropertyRowMapper<Emp>(Emp.class));  
}  
public List<Emp> getEmployees(){  
    return template.query("select * from Emp99", new RowMapper<Emp>(){  
        public Emp mapRow(ResultSet rs, int row) throws SQLException {  
            Emp e=new Emp();  
            e.setId(rs.getInt(1));  
            e.setName(rs.getString(2));  
            e.setSalary(rs.getFloat(3));  
            e.setDesignation(rs.getString(4));  
            return e;  
        }  
    });  
}  
}

5.在web.xml文件中提供控制器的条目

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>SpringMVC</display-name>
   <servlet>  
    <servlet-name>spring</servlet-name>  
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>  
    <load-on-startup>1</load-on-startup>    
</servlet>  
<servlet-mapping>  
    <servlet-name>spring</servlet-name>  
    <url-pattern>/</url-pattern>  
</servlet-mapping>  
</web-app>

6.在xml文件中定义bean

spring-servlet.xml

<?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:context="http://www.springframework.org/schema/context"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="
		http://www.springframework.org/schema/beans
    	http://www.springframework.org/schema/beans/spring-beans.xsd
    	http://www.springframework.org/schema/context
    	http://www.springframework.org/schema/context/spring-context.xsd
    	http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd">
<context:component-scan base-package="com.srcmini.controllers"></context:component-scan>  
  
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">  
<property name="prefix" value="/WEB-INF/jsp/"></property>  
<property name="suffix" value=".jsp"></property>  
</bean>  
  
<bean id="ds" class="org.springframework.jdbc.datasource.DriverManagerDataSource">  
<property name="driverClassName" value="com.mysql.jdbc.Driver"></property>  
<property name="url" value="jdbc:mysql://localhost:3306/test"></property>  
<property name="username" value=""></property>  
<property name="password" value=""></property>  
</bean>  
  
<bean id="jt" class="org.springframework.jdbc.core.JdbcTemplate">  
<property name="dataSource" ref="ds"></property>  
</bean>  
  
<bean id="dao" class="com.srcmini.dao.EmpDao">  
<property name="template" ref="jt"></property>  
</bean>     
</beans>

7.创建请求的页面

index.jsp

<a href="empform">Add Employee</a>
<a href="viewemp">View Employees</a>

8.创建其他视图组件

empform.jsp

<%@ taglib uri="http://www.springframework.org/tags/form" prefix="form"%>  
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>  

		<h1>Add New Employee</h1>
       <form:form method="post" action="save">  
      	<table >  
         <tr>  
          <td>Name : </td> 
          <td><form:input path="name"  /></td>
         </tr>  
         <tr>  
          <td>Salary :</td>  
          <td><form:input path="salary" /></td>
         </tr> 
         <tr>  
          <td>Designation :</td>  
          <td><form:input path="designation" /></td>
         </tr> 
         <tr>  
          <td> </td>  
          <td><input type="submit" value="Save" /></td>  
         </tr>  
        </table>  
       </form:form>

empeditform.jsp

这里的” / SpringMVCCRUDSimple”是项目名称, 如果你有不同的项目名称, 请更改此名称。对于实时应用程序, 你可以提供完整的URL。

<%@ taglib uri="http://www.springframework.org/tags/form" prefix="form"%>  
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>  

		<h1>Edit Employee</h1>
       <form:form method="POST" action="/SpringMVCCRUDSimple/editsave">  
      	<table >  
      	<tr>
      	<td></td>  
         <td><form:hidden  path="id" /></td>
         </tr> 
         <tr>  
          <td>Name : </td> 
          <td><form:input path="name"  /></td>
         </tr>  
         <tr>  
          <td>Salary :</td>  
          <td><form:input path="salary" /></td>
         </tr> 
         <tr>  
          <td>Designation :</td>  
          <td><form:input path="designation" /></td>
         </tr> 
         
         <tr>  
          <td> </td>  
          <td><input type="submit" value="Edit Save" /></td>  
         </tr>  
        </table>  
       </form:form>

viewemp.jsp

<%@ taglib uri="http://www.springframework.org/tags/form" prefix="form"%>  
    <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>  

	<h1>Employees List</h1>
	<table border="2" width="70%" cellpadding="2">
	<tr><th>Id</th><th>Name</th><th>Salary</th><th>Designation</th><th>Edit</th><th>Delete</th></tr>
    <c:forEach var="emp" items="${list}"> 
    <tr>
    <td>${emp.id}</td>
    <td>${emp.name}</td>
    <td>${emp.salary}</td>
    <td>${emp.designation}</td>
    <td><a href="editemp/${emp.id}">Edit</a></td>
    <td><a href="deleteemp/${emp.id}">Delete</a></td>
    </tr>
    </c:forEach>
    </table>
    <br/>
    <a href="empform">Add New Employee</a>

输出

单击添加员工后, 你将看到以下表格。

填写表单, 然后单击”保存”以将条目添加到数据库中。

现在, 单击”编辑”以对提供的数据进行一些更改。

现在, 单击”编辑保存”以将具有更改的条目添加到数据库中。

现在, 单击”删除”以从数据库中删除条目。

下载此示例(使用Eclipse开发)

下载SQL文件

下载SQL文件

下载MYSQL-connector.jar文件

如果你不使用maven, 请下载MYSQL-connector.jar。