当你写一段代码很纠结时，不防停下来Google一下，一定有人已经解决了你的烦恼！

一、背景

今天PM提出想给一个URL埋点，统计一下访问来源，需要我在路径上加一个参数fromPage=shop_detail;本来是一个很简单的问题，因为原链接根本没参数，只只需要在url后面加上?fromPage=shop_detail；可想了一下有安全隐患，万一url变了，带了参数怎么办？于是想那我就自己判断是否有参数，再决定加?或/;当我下手写的时候又纠结了，为了这么一点东西要写好几行代码呢，不行，还是得先google 一下，就有了如下结论。

二、添加parameter的方式

2.1 java.net.URI

通过string 生成URI，再通过URI获取query,再通过query判断是添加&或?; 似乎也挺麻烦……

package urItest;

import java.net.URI;
import java.net.URISyntaxException;

/**
 * Created by fuxiangxu on 2017/1/10.
 */
public class URITest {
    public static URI appendUri(String uri, String appendQuery) throws URISyntaxException {
        URI oldUri = new URI(uri);

        String newQuery = oldUri.getQuery();
        if (newQuery == null) {
            newQuery = appendQuery;
        } else {
            newQuery += "&" + appendQuery;
        }

        URI newUri = new URI(oldUri.getScheme(), oldUri.getAuthority(),
                oldUri.getPath(), newQuery, oldUri.getFragment());

        return newUri;
    }

    public static void main(String[] args) throws Exception {
        System.out.println(appendUri("http://example.com", "name=John"));
        System.out.println(appendUri("http://example.com#fragment", "name=John"));
        System.out.println(appendUri("http://example.com?email=john.doe@email.com", "name=John"));
        System.out.println(appendUri("http://example.com?email=john.doe@email.com#fragment", "name=John"));
    }
}

2.2 javax.ws.rs.core.UriBuilder

package urItest;

import javax.ws.rs.core.UriBuilder;

import java.net.URISyntaxException;

/**
 * Created by fuxiangxu on 2017/1/10.
 */
public class URIBuilderTest {

    public static void main(String[] args) throws URISyntaxException {
        System.out.println(UriBuilder.fromUri("http://example.com").queryParam("name", "john").build().toString());
        System.out.println(UriBuilder.fromUri("http://example.com?email=john.doe@email.com").queryParam("name", "john").build().toString());
    }
}

2.3 org.apache.http.client.utils.URIBuilder

package urItest;

import org.apache.http.client.utils.URIBuilder;

import java.net.URISyntaxException;

/**
 * Created by fuxiangxu on 2017/1/10.
 */
public class URIBuilderTest {

    public static void main(String[] args) throws URISyntaxException {
        System.out.println(new URIBuilder("http://example.com").addParameter("name", "john").build().toString());
        System.out.println(new URIBuilder("http://example.com?email=john.doe@email.com").addParameter("name", "john").build().toString());
    }
}

2.4 org.springframework.web.util.UriComponentsBuilder (建议)

package urItest;

import org.springframework.web.util.UriComponentsBuilder;

import java.net.URISyntaxException;

/**
 * Created by fuxiangxu on 2017/1/10.
 */
public class URIBuilderTest {

    public static void main(String[] args) throws URISyntaxException {
        System.out.println(UriComponentsBuilder.fromUriString("http://example.com").queryParam("name", "john").build().toString());
        System.out.println(UriComponentsBuilder.fromUriString("http://example.com?email=john.doe@email.com").queryParam("name", "john").build().toString());
    }
}