Apache DBUtils框架 结果处理器
时间：2021-07-01 10:21:17
帮助过：21人阅读
com.itheima.dbutil;
import java.util.List;
import java.util.Map;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.ArrayHandler;
import org.apache.commons.dbutils.handlers.ArrayListHandler;
import org.apache.commons.dbutils.handlers.ColumnListHandler;
import org.apache.commons.dbutils.handlers.KeyedHandler;
import org.apache.commons.dbutils.handlers.MapHandler;
import org.apache.commons.dbutils.handlers.MapListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import org.junit.Test;
import com.itheima.util.DBCPUtil;
public class ResultSetHandlerDemo {
private QueryRunner qr =
new QueryRunner(DBCPUtil.getDataSource());
//ArrayHandler:适合结果只有一条的情况。把第一条记录的每列的值封装到一个Object[]数组中
@Test
public void test1()
throws Exception{
Object[] objs = qr.query("select * from student",
new ArrayHandler());
for(Object obj:objs)
System.out.println(obj);
}
//ArrayListHandler:适合结果有多条的情况。把每列的值封装到Object[]数组中，把Object[]放到List中
@Test
public void test2()
throws Exception{
List<Object[]> list = qr.query("select * from student",
new ArrayListHandler());
for(Object[] objs:list){
System.out.println("----------------"
);
for(Object obj:objs){
System.out.println(obj);
}
}
}
//ColumnListHandler:适合取某列的值。把取到值封装到List中
@Test
public void test3()
throws Exception{
List<Object> list = qr.query("select * from student",
new ColumnListHandler("name"
));
for(Object obj:list){
System.out.println(obj);
}
}
//KeyedHandler:查询多条记录。每条记录封装到一个Map中，key：字段名，value：字段值。再把Map作为value放到另外一个Map中，该Map的key为指定的列值作为key。
@Test
public void test4()
throws Exception{
Map<Object,Map<String,Object>> bmap = qr.query("select * from student",
new KeyedHandler("id"
));
for(Map.Entry<Object,Map<String,Object>>
bme:bmap.entrySet()){
System.out.println("--------------------"
);
for(Map.Entry<String, Object>
lme:bme.getValue().entrySet()){
System.out.println(lme.getKey()+"="+
lme.getValue());
}
}
}
//MapHandler:适合一条结果。封装到一个Map中，key：字段名，value：字段值
@Test
public void test5()
throws Exception{
Map<String,Object> map = qr.query("select * from student",
new MapHandler());
for(Map.Entry<String, Object>
lme:map.entrySet()){
System.out.println(lme.getKey()+"="+
lme.getValue());
}
}
//MapListHandler:适合多条结果。把每条封装到一个Map中，key：字段名，value：字段值，在把Map封装到List中
@Test
public void test6()
throws Exception{
List<Map<String,Object>> list = qr.query("select * from student",
new MapListHandler());
for(Map<String,Object>
map:list){
System.out.println("--------------------"
);
for(Map.Entry<String, Object>
lme:map.entrySet()){
System.out.println(lme.getKey()+"="+
lme.getValue());
}
}
}
//ScalarHandler:适合取结果只有一行和一列的情况。
@Test
public void test7()
throws Exception{
Object obj = qr.query("select count(*) from student",
new ScalarHandler(1
));
// System.out.println(obj.getClass().getName());
Long l =
(Long)obj;
System.out.println(l.intValue());
System.out.println(obj);
}
}
Apache DBUtils框架 结果处理器
标签：gpo getname map resultset handler com dbcp sel 图片
