Spring数据访问策略

Spring封装的数据访问异常
与SQLException是一个Checked Exception不同，Spring定义的基本书籍访问异常DataAccessException是一个RuntimeException，DataAccessException继承自NestedRuntimeException，完整的保留了原始异常信息。

异常	定义
DataAccessException	SpringDAO异常体系跟类
ConcurrencyFailureException	在多个并发访问时，无法乐观锁定或者获得数据库锁等
DataAccessResourceFailureException	访问数据彻底失败，例如无法连接数据库
DataRetrievalFailureException	无法获得指定数据，例如，根据主键无法查到相应记录
InvalidDataAccessResourceUsageException	无效的数据访问方法，使用了语法错误的SQL语句
PermissionDeniedDataAccessException	没有数据访问权限，例如，当前数据库登录用户无权访问特定表
UncategorizedDataAccessException	无法归类的异常

准备数据库环境

// HsqldbUtil类，创建Book表，并插入两条数据
public static void startDatabase() {
    server = new Server();
    server.setDatabaseName(0, "test");
    server.setDatabasePath(0, "mem:bookstore");
    server.setLogWriter(null);
    server.setErrWriter(null);
    server.start();
}

<!-- 定义DataSource -->
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
	<property name="driverClassName" value="org.hsqldb.jdbcDriver" />
	<property name="url" value="jdbc:hsqldb:mem:bookstore" />
	<property name="username" value="sa" />
	<property name="password" value="" />
</bean>
<!-- 使用DriverManagerDataSource为了方便调试  实际中可方便更换为 -->
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
<bean id="dataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
    <property name="jndiName" value="java:comp/env/jdbc/xxxDataSource"/>
</bean>

主键生成策略
1.数据库内置自增 （不好移植）
2.整形字段，程序控制主键自动增长 （集群时要严格控制同步）
3.UUID 根据计算机MAC地址和时间，随机计算生成，唯一 （128位整数，浪费空间）

public interface BookDao {
    List<Book> queryAll();
    List<Book> queryByAuthor(String author);
    void create(Book book);
    void update(Book book);
    void delete(String id);
}

JdbcTemplet

<!-- 注入dataSource -->
<bean id="jdbcTemplateBookDao" class="example.chapter5.JdbcTemplateBookDao">
	<property name="dataSource" ref="dataSource" />
</bean>

public class JdbcTemplateBookDao extends JdbcDaoSupport implements BookDao {
    // ResultSet映射为Bean的方式
    class BookRowMapper implements RowMapper {
        public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
            Book book = new Book();
            book.setId(rs.getString("id"));
            book.setName(rs.getString("name"));
            book.setAuthor(rs.getString("author"));
            return book;
        }
    }

    @SuppressWarnings("unchecked")
    public List<Book> queryAll() {
        return getJdbcTemplate().query(
                "select * from Book",
                new BookRowMapper());
    }

    @SuppressWarnings("unchecked")
    public List<Book> queryByAuthor(String author) {
        return getJdbcTemplate().query(
                "select * from Book where author=?",
                new Object[] { author },
                new BookRowMapper());
    }

    public void create(Book book) {
        getJdbcTemplate().update(
                "insert into Book (id, name, author) values (?, ?, ?)",
                new Object[] {book.getId(), book.getName(), book.getAuthor()});
    }

    public void update(Book book) {
        getJdbcTemplate().update(
                "update Book set name=?, author=? where id=?",
                new Object[] {book.getName(), book.getAuthor(), book.getId()});
    }

    public void delete(String id) {
        getJdbcTemplate().update(
                "delete from Book where id=?",
                new Object[] {id});
    }

}

集成Hibernate
Hibernate管理Java类到数据库表的映射，提供了强大的基于对象的查询语句HQL，大幅减少数据库访问需要编写的代码的SQL语句，通过“方言”，最大限度降低了对特定数据库的依赖。
Hibernate还提供了系列复杂功能来简化数据库操作。
1.延迟加载，不一次取得所有相关联的对象，而是希望访问某个对象是再去数据库读取
2.主动抓取，允许在一个查询操作中就获得所有关联的对象，减少数据库连接次数
3.缓存
4.级联操作，外键关联的表，更新一个表时，需要同时更新其他表，级联删除 级联更新

<bean id="sessionFactory" 
    class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
	<property name="dataSource" ref="dataSource" />
	<property name="annotatedClasses">
		<list>
			<value>example.chapter5.Book</value>
		</list>
	</property>
	<property name="annotatedPackages">
		<list>
			<value>example.chapter5</value>
		</list>
	</property>
	<property name="hibernateProperties">
		<props>
			<prop key="hibernate.dialect">org.hibernate.dialect.HSQLDialect</prop>
			<prop key="hibernate.show_sql">true</prop>
			<prop key="hibernate.jdbc.fetch_size">10</prop>
			<prop key="hibernate.cache.provider_class">org.hibernate.cache.HashtableCacheProvider</prop>
		</props>
	</property>
	<property name="eventListeners">
		<map>
			<entry key="pre-update">
				<bean class="org.hibernate.validator.event.ValidatePreUpdateEventListener" />
			</entry>
			<entry key="pre-insert">
				<bean class="org.hibernate.validator.event.ValidatePreInsertEventListener" />
			</entry>
		</map>
	</property>
</bean>

@Entity(name="Book")
public class Book {
// @Entity 作为数据库表映射 @Id 主键  @Transient不需要持久化字段
    private String id;
    private String name;
    private String author;

    @Id
    @Pattern(regex="[a-z0-9\\-]{36}", message="ID只能由英文字母,数字和-构成,长度为36个字符")
    public String getId() { return id; }
    public void setId(String id) { this.id = id; }

    public String getName() { return name; }
    public void setName(String name) { this.name = name; }

    public String getAuthor() { return author; }
    public void setAuthor(String author) { this.author = author; }
}

public class HibernateBookDao extends HibernateDaoSupport implements BookDao {

    @SuppressWarnings("unchecked")
    public List<Book> queryAll() {
        return getHibernateTemplate().find("select b from Book as b");
    }

    @SuppressWarnings("unchecked")
    public List<Book> queryByAuthor(String author) {
        return getHibernateTemplate().find("select b from Book as b where b.author=?", author);
    }

    public void create(Book book) {
        getHibernateTemplate().save(book);
    }

    public void delete(String id) {
        Book book = (Book) getHibernateTemplate().load(Book.class, id);
        getHibernateTemplate().delete(book);
    }

    public void update(Book book) {
        getHibernateTemplate().update(book);
    }

}

集成Ibtais

<bean id="iBatisBookDao" class="example.chapter5.IBatisBookDao">
	<property name="sqlMapClient">
		<bean class="org.springframework.orm.ibatis.SqlMapClientFactoryBean">
			<property name="configLocation" value="ibatis-sql-map-config.xml" />
			<property name="dataSource" ref="dataSource" />
		</bean>
	</property>
</bean>

public class IBatisBookDao extends SqlMapClientDaoSupport implements BookDao {

    @SuppressWarnings("unchecked")
    public List<Book> queryAll() {
        return getSqlMapClientTemplate().queryForList("queryAll");
    }

    @SuppressWarnings("unchecked")
    public List<Book> queryByAuthor(String author) {
        return getSqlMapClientTemplate().queryForList("queryByAuthor", author);
    }

    public void create(Book book) {
        getSqlMapClientTemplate().insert("create", book);
    }

    public void delete(String id) {
        getSqlMapClientTemplate().delete("delete", id);
    }

    public void update(Book book) {
        getSqlMapClientTemplate().update("update", book);
    }
}

集成JPA
Spring对JPA采用Adapter模式，使JPA和其他持久化机制（Hibernate Toplink JDO）拥有一致的编程模型。

<!--  
  LocalEntityManagerFactoryBean 提供了标准的JPA初始化配置
  LocalContainerEntityManagerFactoryBean 更灵活，可以注入Spring管理的DataSource
-->
<bean id="entityManagerFactory" 
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
	<property name="dataSource" ref="dataSource"/>
	<!-- Adapter 选择实现JPA的具体框架 -->
	<property name="jpaVendorAdapter">
		<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
			<property name="showSql" value="true" />
			<property name="generateDdl" value="false" />
		</bean>
	</property>
</bean> 

<bean id="jpaTxManager" class="org.springframework.orm.jpa.JpaTransactionManager">
	<property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>

<tx:annotation-driven transaction-manager="jpaTxManager" />

public class JpaBookDao extends JpaDaoSupport implements BookDao {

    @SuppressWarnings("unchecked")
    public List<Book> queryAll() {
        return getJpaTemplate().find("select b from Book b");
    }

    @SuppressWarnings("unchecked")
    public List<Book> queryByAuthor(String author) {
        return getJpaTemplate().find("select b from Book b where b.author=?", new Object[] { author });
    }

    public void create(Book book) {
        getJpaTemplate().persist(book);
    }

    public void delete(String id) {
        Book book = getJpaTemplate().find(Book.class, id);
        getJpaTemplate().remove(book);
    }

    public void update(Book book) {
        getJpaTemplate().merge(book);
    }
}