spring mvc：持久层浅析

这里将用到以下几个包：

引用

aopalliance-1.0.jar
commons-collections.jar
commons-dbcp.jar
commons-logging-1.1.1.jar
commons-pool.jar
jstl.jar
log4j-1.2.15.jar
mysql-connector-java-5.1.6-bin.jar
spring-beans-2.5.6.jar
spring-context-2.5.6.jar
spring-context-support-2.5.6.jar
spring-core-2.5.6.jar
spring-jdbc-2.5.6.jar
spring-tx-2.5.6.jar
spring-web-2.5.6.jar
spring-webmvc-2.5.6.jar
standard.jar

主要增加了commons-collections.jar、commons-dbcp.jar、commons-pool.jar、mysql-connector-java-5.1.6-bin.jar和spring-jdbc-2.5.6.jar
先弄个数据库，这里使用MySQL，我的最爱！ 可惜前途未卜！
建库：

CREATE DATABASE `spring` /*!40100 DEFAULT CHARACTER SET utf8 */;

CREATE DATABASE `spring` /*!40100 DEFAULT CHARACTER SET utf8 */;

建表：

DROP TABLE IF EXISTS `spring`.`account`;
CREATE TABLE  `spring`.`account` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `username` varchar(45) NOT NULL,
  `password` varchar(45) NOT NULL,
  `birthday` datetime NOT NULL,
  `email` varchar(45) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

DROP TABLE IF EXISTS `spring`.`account`;
CREATE TABLE  `spring`.`account` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `username` varchar(45) NOT NULL,
  `password` varchar(45) NOT NULL,
  `birthday` datetime NOT NULL,
  `email` varchar(45) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

插入默认数据：

INSERT INTO `spring`.`account`(
 `username`,
 `password`,
 `birthday`,
 `email`)
VALUES(
 'snowolf',
 'zlex',
 '2010-01-01',
 '[email protected]');

INSERT INTO `spring`.`account`(
 `username`,
 `password`,
 `birthday`,
 `email`)
VALUES(
 'snowolf',
 'zlex',
 '2010-01-01',
 '[email protected]');

给出一个数据库查询的结果：

很不巧，为了能让数据查询更有意义，我又要改动Account类：
Account.java

public class Account implements Serializable {

    /**
     * 主键
     */
    private int id;

    /**
     * 用户名
     */
    private String username;

    /**
     * 密码
     */
    private String password;

    /**
     * 生日
     */
    private Date birthday;

    /**
     * Email
     */
    private String email;

        // get方法set方法省略
}

public class Account implements Serializable {

	/**
	 * 主键
	 */
	private int id;
	
	/**
	 * 用户名
	 */
	private String username;
	
	/**
	 * 密码
	 */
	private String password;

	/**
	 * 生日
	 */
	private Date birthday;

	/**
	 * Email
	 */
	private String email;
    
        // get方法set方法省略
}

这样，域对象与数据库表将完成一一对应绑定关系。
再建立一个用于构建数据源配置的文件database.properties
database.properties：

dataSource.driverClassName=com.mysql.jdbc.Driver
dataSource.url=jdbc:mysql://localhost:3306/spring
dataSource.username=root
dataSource.password=admin
dataSource.maxActive=200
dataSource.maxIdle=50
dataSource.maxWait=10000

dataSource.driverClassName=com.mysql.jdbc.Driver
dataSource.url=jdbc:mysql://localhost:3306/spring
dataSource.username=root
dataSource.password=admin
dataSource.maxActive=200
dataSource.maxIdle=50
dataSource.maxWait=10000

该文件位于/WEB-INF/目录下。
接下来，我们需要把它引入spring容器，修改applicationContext.xml：
applicationContext.xml

<context:property-placeholder
    location="/WEB-INF/database.properties" />

	<context:property-placeholder
		location="/WEB-INF/database.properties" />

如果需要引入多个properties文件，可以用逗号分隔。
这时，我们已经引入了数据源配置，我们可以通过修改dao.xml构建基于DBCP的数据源：
dao.xml中dataSource配置

<bean
        id="dataSource"
        class="org.apache.commons.dbcp.BasicDataSource"
        destroy-method="close"
        lazy-init="false"
        p:driverClassName="${dataSource.driverClassName}"
        p:url="${dataSource.url}"
        p:username="${dataSource.username}"
        p:password="${dataSource.password}"
        p:maxActive="${dataSource.maxActive}"
        p:maxIdle="${dataSource.maxIdle}"
        p:maxWait="${dataSource.maxWait}" />

<bean
		id="dataSource"
		class="org.apache.commons.dbcp.BasicDataSource"
		destroy-method="close"
		lazy-init="false"
		p:driverClassName="${dataSource.driverClassName}"
		p:url="${dataSource.url}"
		p:username="${dataSource.username}"
		p:password="${dataSource.password}"
		p:maxActive="${dataSource.maxActive}"
		p:maxIdle="${dataSource.maxIdle}"
		p:maxWait="${dataSource.maxWait}" />

上述配置稀松平常，没有什么好阐述的内容，这与一般spring配置无异样。
需要注意的是这个jdbcTemplate配置！
dao.xml中jdbcTemplate配置

<bean
    class="org.springframework.jdbc.core.JdbcTemplate"
    p:dataSource-ref="dataSource" />

	<bean
		class="org.springframework.jdbc.core.JdbcTemplate"
		p:dataSource-ref="dataSource" />

这个配置很关键，如果你要使用其他的ORM框架，同样需要配置这样的模板类，在Dao实现中无需继承JdbcDaoSupport类。
不需要明确JdbcTemplate的id（id="jdbcTemplate"）吗？不再需要了！
AccountDao.java

public interface AccountDao {

    /**
     * 读取账户信息
     *
     * @param username
     * @return
     */
    Account read(String username);

    /**
     * 读取账户信息
     *
     * @param id
     * @return
     */
    Account read(int id);
}

public interface AccountDao {

	/**
	 * 读取账户信息
	 * 
	 * @param username
	 * @return
	 */
	Account read(String username);

	/**
	 * 读取账户信息
	 * 
	 * @param id
	 * @return
	 */
	Account read(int id);
}

AccountDaoImpl.java

/**
 * 2010-1-23
 */
package org.zlex.spring.dao.impl;

import java.sql.ResultSet;
import java.sql.SQLException;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.stereotype.Repository;
import org.zlex.spring.dao.AccountDao;
import org.zlex.spring.domain.Account;

/**
 * 账户数据库实现
 *
 * @author <a href="mailto:[email protected]">梁栋</a>
 * @version 1.0
 * @since 1.0
 */
@Repository
public class AccountDaoImpl implements AccountDao {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Override
    public Account read(String username) {
        String sql = "SELECT * From account WHERE username = ?";
        return (Account) jdbcTemplate.queryForObject(sql,
                new Object[] { username }, accountRowMap);
    }

    @Override
    public Account read(int id) {
        String sql = "SELECT * From account WHERE id = ?";
        return (Account) jdbcTemplate.queryForObject(sql, new Object[] { id },
                accountRowMap);
    }

    protected RowMapper accountRowMap = new RowMapper() {
        @Override
        public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
            Account account = new Account();
            account.setId(rs.getInt("id"));
            account.setUsername(rs.getString("username"));
            account.setPassword(rs.getString("password"));
            account.setBirthday(rs.getDate("birthday"));
            account.setEmail(rs.getString("email"));
            return account;
        }
    };
}

/**
 * 2010-1-23
 */
package org.zlex.spring.dao.impl;

import java.sql.ResultSet;
import java.sql.SQLException;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.stereotype.Repository;
import org.zlex.spring.dao.AccountDao;
import org.zlex.spring.domain.Account;

/**
 * 账户数据库实现
 * 
 * @author <a href="mailto:[email protected]">梁栋</a>
 * @version 1.0
 * @since 1.0
 */
@Repository
public class AccountDaoImpl implements AccountDao {

	@Autowired
	private JdbcTemplate jdbcTemplate;

	@Override
	public Account read(String username) {
		String sql = "SELECT * From account WHERE username = ?";
		return (Account) jdbcTemplate.queryForObject(sql,
				new Object[] { username }, accountRowMap);
	}

	@Override
	public Account read(int id) {
		String sql = "SELECT * From account WHERE id = ?";
		return (Account) jdbcTemplate.queryForObject(sql, new Object[] { id },
				accountRowMap);
	}

	protected RowMapper accountRowMap = new RowMapper() {
		@Override
		public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
			Account account = new Account();
			account.setId(rs.getInt("id"));
			account.setUsername(rs.getString("username"));
			account.setPassword(rs.getString("password"));
			account.setBirthday(rs.getDate("birthday"));
			account.setEmail(rs.getString("email"));
			return account;
		}
	};
}

分段详述：
注解@Repository明确这个类是用于持久层的实现类，注意这样的注解不能用于接口，仅适用于实现类！
同时，不再需要继承JdbcDaoSupport类，其而代之的是直接注入JdbcTemplate类！
再看声明JdbcTemplate类：

@Autowired
private JdbcTemplate jdbcTemplate;

	@Autowired
	private JdbcTemplate jdbcTemplate;

需要说明一下，这里的JdbcTemplate对象jdbcTemplate名称可以自定，没有任何限制！
这里使用 RowMapper 定义了一个用于绑定Account域对象的内部映射类：
RowMapper

protected RowMapper accountRowMap = new RowMapper() {
    @Override
    public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
        Account account = new Account();
        account.setId(rs.getInt("id"));
        account.setUsername(rs.getString("username"));
        account.setPassword(rs.getString("password"));
        account.setBirthday(rs.getDate("birthday"));
        account.setEmail(rs.getString("email"));
        return account;
    }
};

	protected RowMapper accountRowMap = new RowMapper() {
		@Override
		public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
			Account account = new Account();
			account.setId(rs.getInt("id"));
			account.setUsername(rs.getString("username"));
			account.setPassword(rs.getString("password"));
			account.setBirthday(rs.getDate("birthday"));
			account.setEmail(rs.getString("email"));
			return account;
		}
	};

语句级的内容，十分简单，如下所示：

@Override
public Account read(String username) {
    String sql = "SELECT * From account WHERE username = ?";
    return (Account) jdbcTemplate.queryForObject(sql,
            new Object[] { username }, accountRowMap);
}

@Override
public Account read(int id) {
    String sql = "SELECT * From account WHERE id = ?";
    return (Account) jdbcTemplate.queryForObject(sql, new Object[] { id },
            accountRowMap);
}

	@Override
	public Account read(String username) {
		String sql = "SELECT * From account WHERE username = ?";
		return (Account) jdbcTemplate.queryForObject(sql,
				new Object[] { username }, accountRowMap);
	}

	@Override
	public Account read(int id) {
		String sql = "SELECT * From account WHERE id = ?";
		return (Account) jdbcTemplate.queryForObject(sql, new Object[] { id },
				accountRowMap);
	}

写完这两段代码不由感慨，我曾经就这么噼里啪啦的敲了一年多这样的代码。不断的做绑定、映射、写SQL，直到可以有机会将持久层JDBC实现替换Hibernate、iBatis，我才得以解放！
接着，再调整一下Service实现类
AccountServiceImpl.java

public class AccountServiceImpl implements AccountService {

    @Autowired
    private AccountDao accountDao;

    @Override
    public Account read(String username, String password) {
        Account account = accountDao.read(username);

        if (!password.equals(account.getPassword())) {
            account = null;
        }
        return account;
    }

    @Override
    public Account read(int id) {
        return accountDao.read(id);
    }
}

public class AccountServiceImpl implements AccountService {

	@Autowired
	private AccountDao accountDao;

	@Override
	public Account read(String username, String password) {
		Account account = accountDao.read(username);

		if (!password.equals(account.getPassword())) {
			account = null;
		}
		return account;
	}

	@Override
	public Account read(int id) {
		return accountDao.read(id);
	}
}

使用AccountDao接口来完成响应的操作，逻辑部分不做详述，根据业务逻辑而定！
稍稍修改一下profile.jsp，将用户的生日、邮件地址都输出出来！

<fieldset><legend>用户信息</legend>
<ul>
    <li><label>用户名:</label><c:out value="${account.username}" /></li>
    <li><label>生日:</label><fmt:formatDate value="${account.birthday}"
        pattern="yyyy年MM月dd日" /></li>
    <li><label>Email:</label><c:out value="${account.email}" /></li>
</ul>
</fieldset>
标签<fmt:formatDate />用于格式化输出，大家可以了解一下，很简单很好用的标签！ :D

<fieldset><legend>用户信息</legend>
<ul>
	<li><label>用户名:</label><c:out value="${account.username}" /></li>
	<li><label>生日:</label><fmt:formatDate value="${account.birthday}"
		pattern="yyyy年MM月dd日" /></li>
	<li><label>Email:</label><c:out value="${account.email}" /></li>
</ul>
</fieldset>
标签<fmt:formatDate />用于格式化输出，大家可以了解一下，很简单很好用的标签！ :D 

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