声明：本栏目所使用的素材都是凯哥学堂VIP学员所写，学员有权匿名，对文章有最终解释权；凯哥学堂旨在促进VIP学员互相学习的基础上公开笔记。 使用依赖注入做一个增删查改的小例题pom.xml文件配置如下： <dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>4.3.14.RELEASE</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.39</version>
</dependency>
<dependency>
<groupId>com.mchange</groupId>
<artifactId>c3p0</artifactId>
<version>0.9.5.2</version>
</dependency>
<dependency>
<groupId>org.json</groupId>
<artifactId>json</artifactId>
<version>20160810</version>
</dependency>
</dependencies>
Spring配置文件内容如下： <?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: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.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd
">
<context:annotation-config/>
<context:component-scan base-package="org.zero01"/>
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
p:driverClass="com.mysql.jdbc.Driver"
p:jdbcUrl="jdbc:mysql:///school"
p:user="root"
p:password="your_password"
p:maxPoolSize="10"
p:minPoolSize="1"
p:loginTimeout="2000"
/>
</beans>
首先是接口代码： package org.zero01.dao;
import org.zero01.pojo.Student;
import java.util.List;
public interface DAO {
public int insert(Student student) throws Exception;
public int delete(int sid) throws Exception;
public List<Student> selectAll() throws Exception;
public int update(Student student) throws Exception;
}
package org.zero01.service;
import org.zero01.pojo.Student;
import java.util.List;
public interface Service {
public int enterSchool(Student student);
public int dropOut(int sid);
public List<Student> getStudents();
public int updateData(Student student);
}
package org.zero01.view;
import org.zero01.pojo.Student;
import java.util.List;
public interface View {
public int enterSchool(Student student);
public int dropOut(int sid);
public List<Student> getStudents();
public int updateData(Student student);
}
然后是具体的实现类代码，StudentDAO类： package org.zero01.dao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.zero01.pojo.Student;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
@Component("stuDAO")
public class StudentDAO implements DAO {
@Autowired
private DataSource dataSource;
public int insert(Student student) throws Exception {
Connection connection = null;
try {
connection = dataSource.getConnection();
String sql = "INSERT INTO student(sname,age,sex,address) VALUES (?,?,?,?)";
PreparedStatement preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1, student.getSname());
preparedStatement.setInt(2, student.getAge());
preparedStatement.setString(3, student.getSex());
preparedStatement.setString(4, student.getAddress());
int row = preparedStatement.executeUpdate();
if (row > 0) {
return row;
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
connection.close();
}
return 0;
}
public int delete(int sid) throws Exception {
Connection connection = null;
try {
connection = dataSource.getConnection();
String sql = "DELETE FROM student WHERE sid=?";
PreparedStatement preparedStatement = connection.prepareStatement(sql);
preparedStatement.setInt(1, sid);
int row = preparedStatement.executeUpdate();
if (row > 0) {
return row;
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
connection.close();
}
return 0;
}
public List<Student> selectAll() throws Exception {
Connection connection = null;
try {
connection = dataSource.getConnection();
String sql = "select * from student";
PreparedStatement preparedStatement = connection.prepareStatement(sql);
ResultSet resultSet = preparedStatement.executeQuery();
List<Student> students = new ArrayList<Student>();
while (resultSet.next()) {
Student student = new Student();
student.setSid(resultSet.getInt("sid"));
student.setSname(resultSet.getString("sname"));
student.setSex(resultSet.getString("sex"));
student.setAddress(resultSet.getString("address"));
students.add(student);
}
return students;
} catch (SQLException e) {
e.printStackTrace();
} finally {
connection.close();
}
return null;
}
public int update(Student student) throws Exception {
Connection connection = null;
try {
connection = dataSource.getConnection();
String sql = "UPDATE student SET sname=?,age=?,sex=?,address=? WHERE sid=?";
PreparedStatement preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1, student.getSname());
preparedStatement.setInt(2, student.getAge());
preparedStatement.setString(3, student.getSex());
preparedStatement.setString(4, student.getAddress());
preparedStatement.setInt(5, student.getSid());
int row = preparedStatement.executeUpdate();
if (row > 0) {
return row;
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
connection.close();
}
return 0;
}
}
SchoolService代码： package org.zero01.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.zero01.dao.DAO;
import org.zero01.pojo.Student;
import java.util.List;
@Component("schoolService")
public class SchoolService implements Service {
@Autowired
private DAO dao;
public int enterSchool(Student student) {
try {
return dao.insert(student);
} catch (Exception e) {
e.printStackTrace();
}
return 0;
}
public int dropOut(int sid) {
try {
return dao.delete(sid);
} catch (Exception e) {
e.printStackTrace();
}
return 0;
}
public List<Student> getStudents() {
try {
return dao.selectAll();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
public int updateData(Student student) {
try {
return dao.update(student);
} catch (Exception e) {
e.printStackTrace();
}
return 0;
}
}
SchoolAction代码： package org.zero01.view;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.zero01.pojo.Student;
import org.zero01.service.Service;
import java.util.List;
@Component("stuAction")
public class SchoolAction implements View {
@Autowired
private Service schoolService;
public int enterSchool(Student student) {
return schoolService.enterSchool(student);
}
public int dropOut(int sid) {
return schoolService.dropOut(sid);
}
public List<Student> getStudents() {
return schoolService.getStudents();
}
public int updateData(Student student) {
return schoolService.updateData(student);
}
}
从以上的代码可以看到，我们没有在哪一个类里写了关于任何实例化对象的代码，而是把实例化这项工作交给Spring容器去帮我们完成，这样每个类都不需要去管理、维护自己的依赖对象，只需要完成自己业务代码即可，这样弱化了类与类之间的依赖，让代码的复杂度降低，每个类都只需要维护自己的业务代码即可，这是Spring的IOC模块给我们带来的好处。而且每个类都依赖的是接口，而不是具体的实现类，符合依赖倒转原则，不会导致代码紧耦合，当具体的实现类被替换时，不会影响到其他类。 测试代码： package org.zero01;
import org.json.JSONObject;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.zero01.view.View;
import org.zero01.pojo.Student;
import java.util.HashMap;
import java.util.Map;
public class Test {
public static void main(String[] args) {
ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
View view = (View) app.getBean("stuAction");
Student student = (Student) app.getBean("student");
System.out.println("enterSchool() 影响行数：" + view.enterSchool(student));
System.out.println("dropOut() 影响行数：" + view.dropOut(25));
Map<String, Object> map = new HashMap<String, Object>();
map.put("studentList", view.getStudents());
map.put("length", view.getStudents().size());
System.out.println(new JSONObject(map));
student.setSname("小刚");
student.setAddress("长沙");
student.setAge(18);
student.setSid(29);
System.out.println("updateData() 影响行数：" + view.updateData(student));
}
}
运行结果： enterSchool() 影响行数：1
dropOut() 影响行数：1
{
"studentList": [
{
"address": "南京",
"sname": "小明",
"sex": "男",
"age": 0,
"sid": 26
},
{
"address": "南京",
"sname": "
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