Saturday, June 13, 2015

Java RegEx: How to replace all with pre-processing on a captured group

Need to replace all occurances of a pattern text and replace it with a captured group? Something like this in Java works nicely:

        String html = "<a href='myurl?id=1123'>myurl</a>\n" +
                "<a href='myurl2?id=2123'>myurl2</a>\n" +
                "<a href='myurl3?id=3123'>myurl3</a>";
        html = html.replaceAll("id=(\\w+)'?", "productId=$1'");

Here I swapped the query name from "id" to "productId" on all the links that matched my criteria. But what happen if I needed to pre-process the captured ID value before replacing it? Let's say now I want to do a lookup and transform the ID value to something else?

This extra requirement would lead us to dig deeper into Java RegEx package. Here is what I come up with:

import java.util.regex.*;
    public String replaceAndLookupIds(String html) {
        StringBuffer newHtml = new StringBuffer();
        Pattern p = Pattern.compile("id=(\\w+)'?");
        Matcher m = p.matcher(html);
        while (m.find()) {
            String id=;
            String newId = lookup(id);
            String rep = "productId=" + newId + "'";
            m.appendReplacement(newHtml, rep);
        return newHtml.toString();

Saturday, June 6, 2015

Example of plain Jdbc Support Class

Need to fetch some data from DB quickly with Java? Here is a quick example of plain JDBC JdbcSupport Class to help you.

package zemian.jdbcexample

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public abstract class JdbcSupport {
    private static final Logger LOGGER = LoggerFactory.getLogger(JdbcSupport.class);

    protected DataSource dataSource;

    public JdbcSupport(DataSource dataSource) throws Exception {
        this.dataSource = dataSource;

    protected Row toRowMap(ResultSet rs) throws Exception {
        Row row = new Row();
        ResultSetMetaData meta = rs.getMetaData();
        int count = meta.getColumnCount();
        for (int i=1; i <= count; i++) {
  , rs.getObject(i));
        return row;

    protected List<Row> queryRowList(Connection conn, String sql, Object... params) throws Exception {
        LOGGER.debug("Query sql={}, params={}", sql, Arrays.asList(params));
        List<Row> result = new ArrayList<>();
        try(PreparedStatement st = conn.prepareStatement(sql)) {
            for (int i = 1; i <= params.length; i++) {
                st.setObject(i, params[i -1]);
            try (ResultSet rs = st.executeQuery()) {
                while( {
        return result;

    protected Row queryRow(Connection conn, String sql, Object... params) throws Exception {
        List<Row> rowList = queryRowList(conn, sql, params);
        if (rowList.size() != 1) {
            throw new RuntimeException("No unique result from query.");
        return rowList.get(0);
    public static class Row {
        public Map<String, Object> map = new HashMap<>();

        public <T> T get(String name) {
            T result = (T)map.get(name);
            return result;

        public <T> T get(String name, T defVal) {
            T result = (T)map.get(name);
            if (result == null)
                return defVal;
            return result;

To use it, one may do something like this:

public class AccountStore extends JdbcSupport {
    public AccountStore(DataSource dataSource) {
    public void printAccountProfiles() {
        try(Connection conn = dataSource.getConnection()) {
            Row row = queryRow(conn, sql, "zemian");
            String accountId = row.get("ACCOUNTID");
            String department = "IT";
            List<Row> rowList = queryRowList(conn, sql, accountId, department);
            for (Row row : rowList) {
                System.out.println("Got profile: " +;