Spring之DAO一

前面博客把bean、aop簡單了解了一下，今天主要是了解Spring中DAO層，如果使用傳統的JDBC時需要創建連接、打開、執行sql、關閉連接這一系列的步驟，Spring框架對JDBC進行了封裝，我們只需使用封裝好的JdbcTemplate執行sql語句。主要還是繼承了Spring提供的JdbcDaoSupport。下面主要是用來演示怎么使用JdbcDaoSupport。

一、創建Model

這里創建一個User類，作為model。

package Cuiyw.Spring.Model;

public class User {
    private int userId;
    public int getUserId() {
        return userId;
    }
    public void setUserId(int userId) {
        this.userId = userId;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    private String name;
    
    
    private float money;
    public float getMoney() {
        return money;
    }
    public void setMoney(float money) {
        this.money = money;
    }

}

二、創建DAO接口並實現接口

1.這里創建IUserDAO接口，聲明了兩個方法，一個是獲取所有的User，一個是新增User。

package Cuiyw.Spring.IDao;

import java.util.*;

import Cuiyw.Spring.Model.User;

public interface IUserDAO {
    
    public List<User>QueryAllUser();
    
    public Boolean AddUser(String name,float money);
    
}

2.這里實現接口IUserDAO,並且繼承JdbcDaoSupport。在下面的代碼中能找到getJdbcTemplate()，其實我們右鍵選擇Open declaration 時可以定位到抽象類JdbcDaoSupport，JdbcDaoSupport里面有一個JdbcTemplate屬性，而且還有get或set JDBC DataSource，然后選中JdbcTemplate，再Open declaration,發現JdbcTemplate的構造函數需要DataSource，JdbcDaoSupport提供JdbcTemplate對象，並維護着JdbcTemplate對象需要的DataSource。

package Cuiyw.Spring.Dao;

import java.util.*;

import org.springframework.jdbc.core.support.JdbcDaoSupport;

import Cuiyw.Spring.IDao.IUserDAO;
import Cuiyw.Spring.Model.User;


public class UserDAO extends JdbcDaoSupport implements IUserDAO {

    public List<User> QueryAllUser() {
        
        String sql="select id,name,money from tb_user";
        List<Map<String,Object>> list=getJdbcTemplate().queryForList(sql);
        List<User> userList=new ArrayList<User>();
        for(Map<String,Object> row:list)
        {
            User user=new User();
            user.setUserId((Integer)row.get("id"));
            user.setName((String)row.get("name"));
            user.setMoney((Float)row.get("money"));
            userList.add(user);
        }
        return userList;
        
    }

    public Boolean AddUser(String name,float money) {
        String sql="insert into tb_user (name,money) values (?,?)";
        int row=getJdbcTemplate().update(sql, new Object[]{name,money});
        if(row>0)
        {
            return true;
        }
        return false;
    }

}

    public JdbcTemplate(DataSource dataSource) {
        setDataSource(dataSource);
        afterPropertiesSet();
    }

3.上下文配置

上面DataSource從哪里來呢?就需要在上下文中配置。首先配置DataSource，然后由於UserDAO繼承了抽象類JdbcDaoSupport，所以也需要設置屬性dataSource

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:aop="http://www.springframework.org/schema/aop"
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
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop.xsd
">
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
  <property name="driverClassName"> 
          <value>com.mysql.jdbc.Driver</value>
  </property>
  <property name="url">
          <value>jdbc:mysql://localhost:3306/spring</value>
  </property>
  <property name="username">
          <value>root</value>
  </property>
  <property name="password">
      <value>123456</value>
  </property> 
</bean> 
<bean id="userDao" class="Cuiyw.Spring.Dao.UserDAO" depends-on="dataSource">
    <property name="dataSource" ref="dataSource"></property>
</bean>
</beans>

4.Mysql新增數據庫和表

上面2中UserDAO執行了兩個sql，涉及到表tb_user，字段id、name、money。在3上下文配置mysql時指定了數據庫名spring。所以按照上面的創建。

5.實驗

        ApplicationContext context=new ClassPathXmlApplicationContext(new String[]{"ApplicationContext.xml"});
        BeanFactory factory=context;
        IUserDAO userDao=(IUserDAO)factory.getBean("userDao");
        userDao.AddUser("cuiywA",888);
    
        userDao.AddUser("cuiywB",666);
        List<User> list=userDao.QueryAllUser(); 
        for(User u:list)
        {
            System.out.println("name:"+u.getName()+" money: "+u.getMoney());
        }

6.錯誤

在實現上面的步驟時報了好幾個錯誤，有因為我疏忽的，還有數據類型和數據庫不一直的，最重要的兩個我這里也記錄了下來。

1.下面的錯誤是由於缺少commons-dbcp.jar、commons-pool.jar導致的

Cannot find class [org.apache.commons.dbcp.BasicDataSource] for bean with name 'dataSource' defined in class path resource [ApplicationContext.xml]; nested exception is java.lang.ClassNotFoundException: org.apache.commons.dbcp.BasicDataSource

2.還有就是我在UserDAO中繼承了JdbcDaoSupport，但就是沒自動提示要引入的包，這個第一次沒經驗，百度了才指定需要引入spring-jdbc.jar.

3.忘記引入mysql驅動

Failed to obtain JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot load JDBC driver class 'com.mysql.jdbc.Driver'

上面的錯誤都是沒有引入jar包，這里把pom.xml也放進來，留着以后好用。

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>Cuiyw</groupId>
  <artifactId>SpringAop</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>SpringAop</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <spring.version>5.0.0.RELEASE</spring.version>
  </properties>

  <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>
       
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>commons-dbcp</groupId>
            <artifactId>commons-dbcp</artifactId>
            <version>1.4</version>
        </dependency>
        <dependency>
            <groupId>commons-pool</groupId>
            <artifactId>commons-pool</artifactId>
            <version>1.6</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        
        <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>3.8.1</version>
          <scope>test</scope>
        </dependency>
            <!-- https://mvnrepository.com/artifact/aspectj/aspectjweaver -->
        <dependency>
            <groupId>aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.5.4</version>
        </dependency>
            <!-- https://mvnrepository.com/artifact/aspectj/aspectjrt -->
        <dependency>
            <groupId>aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>1.5.4</version>
        </dependency>
    
  </dependencies>
</project>