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SpringMVC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。
创建一个表
在这里，我们使用的是MySQL数据库中存在的emp99表。它具有4个字段: ID，名称，薪水和名称。
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类包含对应于数据库中存在的字段的变量(以及setter和getter方法)。
Emp.java
package com.div.cn.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.div.cn.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.div.cn.beans.Emp;
import com.div.cn.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("//spring//spring/empform")
public String showform(Model m){
m.addAttribute("command", new Emp());
return "/spring//spring/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://spring/viewemp";//will redirect to /spring/viewemp request mapping
}
/* It provides list of employees in model object */
@RequestMapping("//spring/viewemp")
public String /spring/viewemp(Model m){
List<Emp> list=dao.getEmployees();
m.addAttribute("list",list);
return "/spring/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://spring/viewemp";
}
/* It deletes record for the given id in URL and redirects to //spring/viewemp */
@RequestMapping(value="/deleteemp/{id}",method = RequestMethod.GET)
public String delete(@PathVariable int id){
dao.delete(id);
return "redirect://spring/viewemp";
}
}
4、创建DAO类
让我们创建一个DAO类以访问数据库中所需的数据。
EmpDao.java
package com.div.cn.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.div.cn.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.div.cn.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.div.cn.dao.EmpDao"> <property name="template" ref="jt"></property> </bean> </beans>
7、创建请求的页面
index.jsp
<a href="/spring//spring/empform">Add Employee</a> <a href="/spring/viewemp">View Employees</a>
8、创建其他视图组件
/spring//spring/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
此处"/SpringMVCCRUDSimple"是项目名称，如果您使用其他项目名称，请更改此名称。对于实时应用程序，您可以提供完整的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>
/spring/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>${emp.designation}</td>
<td><a href="/spring/editemp/${emp.id}">Edit</a></td>
<td><a href="/spring/deleteemp/${emp.id}">Delete</a></td>
</tr>
</c:forEach>
</table>
<br/>
<a href="/spring//spring/empform">Add new Employee</a>
输出:
点击 添加员工时，您将看到以下表格。
填写表格，然后 单击保存以将条目添加到数据库中。
现在，点击 编辑以对提供的内容进行一些更改数据。
现在，单击 编辑保存，将具有更改的条目添加到数据库中。
现在，单击 删除从数据库中删除条目。
