java - UnsatisfiedDependencyException:创建名为“empController”的 bean 时出错
问题描述
我想学习 Spring,所以我编写了简单的 java CRUD 应用程序。但从一开始就有错误org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'empController'
“和org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dao'
我的servlet。我正在寻找一些解决方案,但没有任何效果。
web.xml
<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd" >
<web-app>
<display-name>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>Employer</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Employer</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>
雇主-servlet.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:component-scan base-package="com.javatpoint"></context:component-scan>
<mvc:annotation-driven></mvc:annotation-driven>
<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/Employers"></property>
<property name="username" value="root"></property>
</bean>
<bean id="jt" class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource" ref="ds"></property>
</bean>
<bean id="dao" class="com.javatpoint.EmpDao">
<property name="jdbcTemplate" ref="jt"></property>
</bean>
</beans>
EmpController.java
package com.javatpoint;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
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 org.springframework.web.servlet.ModelAndView;
@Controller
public class EmpController {
@Autowired
EmpDao empDao;
@RequestMapping("/empform")
public ModelAndView show() {
return new ModelAndView("empform", "command", new Emp());
}
@RequestMapping(value="/save", method=RequestMethod.POST)
public ModelAndView save(@ModelAttribute("emp")Emp emp) {
empDao.save(emp);
return new ModelAndView("redirect:/viewemp");
}
@RequestMapping("/viewemp")
public ModelAndView viewemp() {
List<Emp> list = empDao.getEmployees();
return new ModelAndView("viewemp", "list", list);
}
@RequestMapping(value="/editemp/{id}")
public ModelAndView edit(@PathVariable("id")int id) {
Emp emp = empDao.getById(id);
return new ModelAndView("empeditform", "command", emp);
}
@RequestMapping(value="editsave", method=RequestMethod.POST)
public ModelAndView editsave(@ModelAttribute("emp")Emp emp) {
empDao.update(emp);
return new ModelAndView("redirect:/viewemp");
}
@RequestMapping("/delete")
public ModelAndView delete(@ModelAttribute("emp")Emp emp) {
empDao.delete(emp);
return new ModelAndView("redirect:/viewemp");
}
}
EmpDao.java
package com.javatpoint;
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;
public class EmpDao {
private JdbcTemplate jdbcTemplate;
public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
this.jdbcTemplate = jdbcTemplate;
}
public int save(Emp emp) {
String sql = "insert into Employers values('"+emp.getId()+"','"+emp.getName()+"','"+emp.getSalary()+"','"+emp.getDesignation()+"')";
return jdbcTemplate.update(sql);
}
public int update(Emp emp) {
String sql = "update Employers set name='"+emp.getName()+"',salary='"+emp.getSalary()+"',designation='"+emp.getDesignation()+"' where id='"+emp.getId()+"'";
return jdbcTemplate.update(sql);
}
public int delete(Emp emp) {
String sql = "delete from Employers where id='"+emp.getId()+"'";
return jdbcTemplate.update(sql);
}
public Emp getById(int id) {
String sql = "select * form Employers where id=?";
return jdbcTemplate.queryForObject(sql, new Object[] {id}, new BeanPropertyRowMapper<Emp>(Emp.class));
}
public List<Emp> getEmployees(){
return jdbcTemplate.query("select * from Employers", new RowMapper<Emp>() {
public Emp mapRow(ResultSet rs, int row) throws SQLException{
Emp emp = new Emp();
emp.setId(rs.getInt(1));
emp.setName(rs.getString(2));
emp.setSalary(rs.getFloat(3));
emp.setDesignation(rs.getString(4));
return emp;
}
});
}
}
Emp.java
package com.javatpoint;
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;
}
}
解决方案
主要问题是您试图在没有 EmpDao bean 的情况下将 EmpDao 自动连接到您的控制器。
为了使 EmpDao 成为一个 bean,您应该使用 @Component、@Service 或 @Repository 注释 EmpDao 类:
@Service
public class EmpDao {
@Autowired
private JdbcTemplate jdbcTemplate;
public void setJdbcTemplate(JdbcTemplate jdbcTemplate) {
this.jdbcTemplate = jdbcTemplate;
}
public int save(Emp emp) {
String sql = "insert into Employers values('"+emp.getId()+"','"+emp.getName()+"','"+emp.getSalary()+"','"+emp.getDesignation()+"')";
return jdbcTemplate.update(sql);
}
public int update(Emp emp) {
String sql = "update Employers set name='"+emp.getName()+"',salary='"+emp.getSalary()+"',designation='"+emp.getDesignation()+"' where id='"+emp.getId()+"'";
return jdbcTemplate.update(sql);
}
public int delete(Emp emp) {
String sql = "delete from Employers where id='"+emp.getId()+"'";
return jdbcTemplate.update(sql);
}
public Emp getById(int id) {
String sql = "select * form Employers where id=?";
return jdbcTemplate.queryForObject(sql, new Object[] {id}, new BeanPropertyRowMapper<Emp>(Emp.class));
}
public List<Emp> getEmployees(){
return jdbcTemplate.query("select * from Employers", new RowMapper<Emp>() {
public Emp mapRow(ResultSet rs, int row) throws SQLException{
Emp emp = new Emp();
emp.setId(rs.getInt(1));
emp.setName(rs.getString(2));
emp.setSalary(rs.getFloat(3));
emp.setDesignation(rs.getString(4));
return emp;
}
});
}
}
请记住,您只能将其他 bean 注入(或自动装配)到您的 bean 中。
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