Spring 让 LOB 数据操作变得简单易行

Connection getNativeConnection(Connection con)

Connection getNativeConnectionFromStatement(Statement stmt)

PreparedStatement getNativePreparedStatement(PreparedStatement ps)

ResultSet getNativeResultSet(ResultSet rs)

CallableStatement getNativeCallableStatement(CallableStatement cs)

org.springframework.jdbc.support.nativejdbc.WebSphereNativeJdbcExtractor

org.springframework.jdbc.support.nativejdbc.WebLogicNativeJdbcExtractor

org.springframework.jdbc.support.nativejdbc.JBossNativeJdbcExtractor

org.springframework.jdbc.support.nativejdbc.C3P0NativeJdbcExtractor

org.springframework.jdbc.support.nativejdbc.CommonsDbcpNativeJdbcExtractor

org.springframework.jdbc.support.nativejdbc.XAPoolNativeJdbcExtractor

package com.baobaotao.dao.jdbc;

import java.sql.Connection;
import COM.ibm.db2.jdbc.net.DB2Connection;
import org.springframework.jdbc.core.support.JdbcDaoSupport;
import org.springframework.jdbc.datasource.DataSourceUtils;

public class PostJdbcDao extends JdbcDaoSupport implements PostDao {
public void getNativeConn(){
try {
Connection conn = DataSourceUtils.getConnection(getJdbcTemplate()
.getDataSource()); ① 使用 DataSourceUtils 从模板类中获取连接
② 使用模板类的本地 JDBC 抽取器获取本地的 Connection
conn = getJdbcTemplate().getNativeJdbcExtractor().getNativeConnection(conn);
DB2Connection db2conn = (DB2Connection) conn; ③ 这时可以强制进行类型转换了
…
} catch (Exception e) {
e.printStackTrace();
}
}
}

…
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
destroy-method="close">
<property name="driverClassName"
value="${jdbc.driverClassName}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
</bean>
① 定义 DBCP 数据源的 JDBC 本地对象抽取器
<bean id="nativeJdbcExtractor"
class="org.springframework.jdbc.support.nativejdbc.CommonsDbcpNativeJdbcExtractor"
lazy-init="true" />
<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource" ref="dataSource" />
② 设置抽取器
<property name="nativeJdbcExtractor" ref="nativeJdbcExtractor"/>
</bean>
<bean id="postDao" class="com.baobaotao.dao.jdbc.PostJdbcDao">
<property name="jdbcTemplate" ref="jdbcTemplate" />
</bean>

void close()

void setBlobAsBinaryStream(PreparedStatement ps, int paramIndex, InputStream contentStream, int contentLength)

void setBlobAsBytes(PreparedStatement ps, int paramIndex, byte[] content)

void setClobAsAsciiStream(PreparedStatement ps, int paramIndex, InputStream asciiStream, int contentLength)

void setClobAsCharacterStream(PreparedStatement ps, int paramIndex, Reader characterStream, int contentLength)

void setClobAsString(PreparedStatement ps, int paramIndex, String content)

InputStream getBlobAsBinaryStream(ResultSet rs, int columnIndex)

byte[] getBlobAsBytes(ResultSet rs, int columnIndex)

InputStream getClobAsAsciiStream(ResultSet rs, int columnIndex)

Reader getClobAsCharacterStream(ResultSet rs, int columnIndex)

String getClobAsString(ResultSet rs, int columnIndex)

LobCreator getLobCreator()

package com.baobaotao.dao.jdbc;
…
import java.sql.PreparedStatement;
import java.sql.SQLException;
import org.springframework.jdbc.core.support.AbstractLobCreatingPreparedStatementCallback;
import org.springframework.jdbc.support.lob.LobCreator;
import org.springframework.jdbc.support.lob.LobHandler;

public class PostJdbcDao extends JdbcDaoSupport implements PostDao {
private LobHandler lobHandler; ① 定义 LobHandler 属性
public LobHandler getLobHandler() {
return lobHandler;
}
public void setLobHandler(LobHandler lobHandler) {
this.lobHandler = lobHandler;
}
public void addPost(final Post post) {
String sql = " INSERT INTO t_post(post_id,user_id,post_text,post_attach)"
+ " VALUES(?,?,?,?)";
getJdbcTemplate().execute(sql,
new AbstractLobCreatingPreparedStatementCallback(this.lobHandler) { ②
protected void setValues(PreparedStatement ps,LobCreator lobCreator)
throws SQLException {
ps.setInt(1, 1);
ps.setInt(2, post.getUserId());
③ 设置 CLOB 字段
lobCreator.setClobAsString(ps, 3, post.getPostText());
④ 设置 BLOB 字段
lobCreator.setBlobAsBytes(ps, 4, post.getPostAttach());
}
});
}
…
}

…
<bean id="nativeJdbcExtractor"
class="org.springframework.jdbc.support.nativejdbc.CommonsDbcpNativeJdbcExtractor"
lazy-init="true"/>
<bean id="oracleLobHandler"
class="org.springframework.jdbc.support.lob.OracleLobHandler"
lazy-init="true">
<property name="nativeJdbcExtractor" ref="nativeJdbcExtractor"/> ① 设置本地 Jdbc 对象抽取器
</bean>
<bean id="postDao" class="com.baobaotao.dao.jdbc.PostJdbcDao">
<property name="lobHandler" ref="oracleLobHandler"/> ② 设置 LOB 处理器
</bean>

<bean id="defaultLobHandler"
class="org.springframework.jdbc.support.lob.DefaultLobHandler"
lazy-init="true"/>
<bean id="postDao" class="com.baobaotao.dao.jdbc.PostJdbcDao">
<property name="lobHandler" ref=" defaultLobHandler"/>
<property name="jdbcTemplate" ref="jdbcTemplate" />
</bean>

package com.baobaotao.dao.jdbc;

import org.springframework.core.io.ClassPathResource;
import org.springframework.test.AbstractDependencyInjectionSpringContextTests;
import org.springframework.util.FileCopyUtils;
import com.baobaotao.dao.PostDao;
import com.baobaotao.domain.Post;
public class TestPostJdbcDaoextends AbstractDependencyInjectionSpringContextTests {
private PostDao postDao;
public void setPostDao(PostDao postDao) {
this.postDao = postDao;
}
protected String[] getConfigLocations() {
return new String[]{"classpath:applicationContext.xml"};
}
public void testAddPost() throws Throwable{
Post post = new Post();
post.setPostId(1);
post.setUserId(2);
ClassPathResource res = new ClassPathResource("temp.jpg"); ① 获取图片资源
byte[] mockImg = FileCopyUtils.copyToByteArray(res.getFile());  ② 读取图片文件的数据
post.setPostAttach(mockImg);
post.setPostText("测试帖子的内容");
postDao.addPost(post);
}
}

public List getAttachs(final int userId){
String sql = "SELECT post_id,post_attach FROM t_post “+
“where user_id =? and post_attach is not null ";
return getJdbcTemplate().query(
sql,new Object[] {userId},
new RowMapper() {
public Object mapRow(ResultSet rs, int rowNum) throws SQLException {
int postId = rs.getInt(1);
① 以二进制数组方式获取 BLOB 数据。
byte[] attach = lobHandler.getBlobAsBytes(rs, 2);
Post post = new Post();
post.setPostId(postId);
post.setPostAttach(attach);
return post;
}
});
}

…
public void getAttach(final int postId,final OutputStream os){ ① 用于接收 LOB 数据的输出流
String sql = "SELECT post_attach FROM t_post WHERE post_id=? ";
getJdbcTemplate().query(
sql, new Object[] {postId},
new AbstractLobStreamingResultSetExtractor() { ② 匿名内部类
③ 处理未找到数据行的情况
protected void handleNoRowFound() throws LobRetrievalFailureException {
System.out.println("Not Found result!");
}
④ 以流的方式处理 LOB 字段
public void streamData(ResultSet rs) throws SQLException, IOException {
InputStream is = lobHandler.getBlobAsBinaryStream(rs, 1);
if (is != null) {
FileCopyUtils.copy(is, os);
}
}
}
);
}

package com.baobaotao.domain;
…
import javax.persistence.Basic;
import javax.persistence.Lob;
import javax.persistence. Column;
@Entity(name = "T_POST")
public class Post implements Serializable {
…
@Lob ①-1 表示该属性是 LOB 类型的字段
@Basic(fetch = FetchType.EAGER) ①-2 不采用延迟加载机制
@Column(name = "POST_TEXT", columnDefinition = "LONGTEXT NOT NULL") ①-3 对应字段类型
private String postText;

@Lob ②-1 表示该属性是 LOB 类型的字段
@Basic(fetch = FetchType. LAZY) ②-2 采用延迟加载机制
@Column(name = "POST_ATTACH", columnDefinition = "BLOB") ②-3 对应字段类型
private byte[] postAttach;
…
｝

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping auto-import="true" default-lazy="false">
<class name="com.baobaotao.domain.Post" table="t_post">
<id name="postId" column="post_id">
<generator class="identity" />
</id>
<property name="userId" column="user_id"/>
<property name="postText" column="post_text"
type="org.springframework.orm.hibernate3.support.ClobStringType"/>①对应 CLOB 字段
<property name="postAttach" column="post_attach"
type="org.springframework.orm.hibernate3.support.BlobByteArrayType"/>② BLOB 字段
<property name="postTime" column="post_time" type="date" />
<many-to-one name="topic" column="topic_id" class="com.baobaotao.domain.Topic" />
</class>
</hibernate-mapping>

…
<bean id="lobHandler" class="org.springframework.jdbc.support.lob.DefaultLobHandler"
lazy-init="true" />
<bean id="sessionFactory"
class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="lobHandler" ref="lobHandler" /> ① 设置 LOB 处理器
…
</bean>

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE sqlMap PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"
"http://ibatis.apache.org/dtd/sql-map-2.dtd">
<sqlMap namespace="Post">
<typeAlias alias="post" type="com.baobaotao.domain.Post"/>
<resultMap id="result" class="post">
<result property="postId" column="post_id"/>
<result property="userId" column="user_id"/>
<result property="postText" column="post_text" ① 读取 CLOB 类型数据
typeHandler="org.springframework.orm.ibatis.support.ClobStringTypeHandler"/>
<result property="postAttach" column="post_attach" ② 读取 BLOB 类型数据
typeHandler="org.springframework.orm.ibatis.support.BlobByteArrayTypeHandler"/>
</resultMap>
<select id="getPost" resultMap="result">
SELECT post_id,user_id,post_text,post_attach,post_time
FROM t_post  WHERE post_id =#postId#
</select>
<insert id="addPost">
INSERT INTO t_post(user_id,post_text,post_attach,post_time)
VALUES(#userId#,
#postText,handler=org.springframework.orm.ibatis.support.ClobStringTypeHandler#, ③
#postAttach,handler=org.springframework.orm.ibatis.support.BlobByteArrayTypeHandler#, ④
#postTime#)
</insert>
</sqlMap>

<bean id="lobHandler" class="org.springframework.jdbc.support.lob.DefaultLobHandler"
lazy-init="true" />
<bean id="sqlMapClient" class="org.springframework.orm.ibatis.SqlMapClientFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="lobHandler" ref="lobHandler" /> ①设置LobHandler
<property name="configLocation"
value="classpath:com/baobaotao/dao/ibatis/sql-map-config.xml" />
</bean>