幾個使用JDBC Template常用的工具類
第一：IntegerRowMapper
代碼：
public class IntegerRowMapper implements RowMapper {
public Object mapRow(ResultSet rs, int index) throws SQLException {
Integer c = new Integer(0);
c = rs.getInt(1);
return c;
}
}
用途：
如SQL只是取數(shù)量時，可以采用這個類減少一些代碼，示例如下：
StringBuilder sb=new StringBuilder();
sb.append(" SELECT");
sb.append(" count(*)");
sb.append(" FROM");
sb.append(" tb_contract");
sb.append(" WHERE");
sb.append(" contract_id='"+id+"' ");
String sql=sb.toString();
List<?> ls = this.getJdbcTemplate().query(sql, (new IntegerRowMapper()));
Integer i = (Integer) ls.get(0);
第二：StringRowMapper
代碼：
public class StringRowMapper implements RowMapper {
public Object mapRow(ResultSet rs, int index) throws SQLException {
String c=new String(rs.getString(1));
return c;
}
}
用途：當(dāng)SQL語句只返回一個字符串類型的定值時，采用這個類能減少部分代碼，示例如下：
StringBuilder sb=new StringBuilder();
sb.append(" select");
sb.append(" user_name as name");
sb.append(" from");
sb.append(" TB_SYS_USER");
sb.append(" where");
sb.append(" user_id='"+userId+"'");
String sql=sb.toString();
List<?> ls = this.getJdbcTemplate().query(sql, (new StringRowMapper()));
String usrName=(String)ls.get(0);
第三：RecordCounter
代碼：
public class RecordCounter{
private String sql;
private JdbcTemplate jdbcTemplate;
/**
* 構(gòu)造函數(shù)
* @param sql
* @param jdbcTemplate
*/
public RecordCounter(String sql,JdbcTemplate jdbcTemplate){
this.sql=sql;
this.jdbcTemplate=jdbcTemplate;
}
/**
* 得到SQL語句查詢到的記錄數(shù)，對外的關(guān)鍵語句
* @author: 何楊（heyanghy@cn.ibm.com）
* @date : Apr 23, 2011
* @time : 11:09:35 AM
* @return
*/
public int getCount() throws Exception{
StringBuilder sb=new StringBuilder();
sb.append(" select ");
sb.append(" count(*) as recordCount ");
sb.append(" from ("+sql+") t ");
String sql=sb.toString();
class MyRowMapper implements RowMapper {
public Object mapRow(ResultSet rs, int index) throws SQLException {
Integer c = new Integer(0);
c=rs.getInt("recordCount");
return c;
}
}
List<?> ls = jdbcTemplate.query(sql, (new MyRowMapper()));
Integer i=(Integer)ls.get(0);
return i.intValue();
}
}
用途：分頁時常需要得到SQL語句查詢得到的總記錄數(shù)，采用這個類可以減少部分代碼。
示例：略
第四：MapRowMapper
代碼：
public class MapRowMapper implements RowMapper {
public Object mapRow(ResultSet rs, int index) throws SQLException {
List<Map<String,String>> ls=new ArrayList<Map<String,String>>();
int n=rs.getMetaData().getColumnCount();
for(int i=1;i<=n;i++){
try{
Map<String,String> map=new HashMap<String,String>();
map.put(rs.getMetaData().getColumnName(i).toLowerCase(), rs.getString(i));
ls.add(map);
}
catch(Exception ex){
continue;
}
}
return ls;
}
}
用途：一般來說，當(dāng)查詢只會返回一條記錄時，如按ID得到一條記錄，會使用這個Mapping器。得到的對象可以用來給對象賦值。示例如下：
StringBuilder sb=new StringBuilder();
sb.append(" select");
sb.append(" *");
sb.append(" from");
sb.append(" TB_CONTRACT ");
sb.append(" where");
sb.append(" contract_id='"+id+"'");
String sql=sb.toString();
List<?> ls = this.getJdbcTemplate().query(sql, (new MapRowMapper()));
Map<String,String> map = new HashMap<String,String>();
List<?> ls2=(List<?>)ls.get(0);
for(Object obj:ls2){
Map<String,String> mapTemp=(Map<String,String>)obj;
map.putAll(mapTemp);
}
第五：NameValueRowMapper
代碼：
public class NameValueRowMapper implements RowMapper {
public Object mapRow(ResultSet rs, int index) throws SQLException {
List<NameValue> ls=new ArrayList<NameValue>();
int n=rs.getMetaData().getColumnCount();
for(int i=1;i<=n;i++){
NameValue nv=new NameValue(rs.getMetaData().getColumnName(i).toLowerCase(),rs.getString(i));
ls.add(nv);
}
return ls;
}
}
public class NameValue extends BaseDomainObj{
private String name;
private String value;
/**
* 無參數(shù)構(gòu)造函數(shù)
*/
public NameValue(){
}
/**
* 雙參數(shù)構(gòu)造函數(shù)
* @param name
* @param value
*/
public NameValue(String name,String value){
this.name=name;
this.value=value;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
public String asXML() {
StringBuilder sb=new StringBuilder();
sb.append("<"+name+">");
sb.append(StringUtils.isBlank(value)?"-":value);
sb.append("</"+name+">");
return sb.toString();
}
}
public class NameValueList extends BaseDomainObj{
// 內(nèi)含NameValue的鏈表
private List<?> list;
/**
* 無參數(shù)構(gòu)造函數(shù)
*/
public NameValueList(){
}
/**
* 帶參數(shù)構(gòu)造函數(shù)
* @param list
*/
public NameValueList(List<?> list){
this.list=list;
}
@SuppressWarnings("unchecked")
public String asXML() {
StringBuilder sb=new StringBuilder();
for(Object obj:list){
List<NameValue> ls=(List<NameValue>)obj;
sb.append("<node>");
for(NameValue nv:ls){
sb.append(nv.asXML());
}
sb.append("</node>");
}
return sb.toString();
}
public void setList(List<?> list) {
this.list = list;
}
public List<?> getList() {
return list;
}
}
說明：將一行記錄轉(zhuǎn)化成一個包含鍵值對的鏈表，在NameValueList的幫助下能方便的把從數(shù)據(jù)庫得到的行集轉(zhuǎn)化為一段XML；
StringBuilder sb=new StringBuilder();
sb.append(" SELECT ");
sb.append(" *");
sb.append(" FROM tb_contract ");
sb.append(" WHERE contract_id='"+id+"'");
String sql=sb.toString();
List<?> ls=this.getJdbcTemplate().query(sql,new NameValueRowMapper());
NameValueList list=new NameValueList(ls);
String xml=list.asXML();