Java httpclient请求form-data格式并设置boundary代码实现方法_Java

在 java 开发中，经常会遇到需要使用 httpclient 发送 form-data 格式请求的场景。本文将详细介绍如何正确地实现这一操作，包括数据格式示例、常见报错及解决方法，以及完整的 java 代码实现。

form-data 数据请求格式样例

我们先看下 form-data 数据的格式是长什么样的。
例如要传输 form-data 的键值对是：
a: aaa
b: bbb
请求的boundary设置如下：
addheader(“content-type”, “multipart/form-data;boundary=----12345”)

实际请求格式会加上boundary，请求示例如下

----12345
content-disposition: form-data; name="a"
aaa
----12345
content-disposition: form-data; name="b"
bbb

postman自动生成的 boundary 如下：

accept-encoding: gzip, deflate, br
connection: keep-alive
content-type: multipart/form-data; boundary=--------------------------477613155954799910398847

报错信息: missingservletrequestparameterexception解决方法

org.springframework.web.bind.missingservletrequestparameterexception

请求headers中的content-type类型不对
addheader(“content-type”, “application/json; charset=utf-8”);
将json换成multipart/form-data
addheader(“content-type”, “multipart/form-data; charset=utf-8; boundary=” + new uuidgenerator().next());

报错信息: no multipart boundary was found 解决方法

org.apache.tomcat.util.http.fileupload.fileuploadexception: the request was rejected because no multipart boundary was found

这个报错是没有设置边界分隔符
解决方法：

headers中添加boundary

addheader("content-type", "multipart/form-data;boundary=" + boundary)

multipart/form-data 请求参数添加boundary

multipartentitybuilder multipartentitybuilder = multipartentitybuilder.create()
        .setcharset(standardcharsets.utf_8)
        // [重要]:设置 setboundary 边界分隔符
        .setboundary(boundary);

java代码实现

【错误】使用 urlencodedformentity 、basicnamevaluepair 请求失败（error）

public static jsonobject test(string url) throws ioexception {
    requestconfig requestconfig = requestconfig.custom().build();
    try (closeablehttpclient httpclient = httpclientbuilder.create().build()) {
        httppost post = new httppost(url);
        list<namevaluepair> list = new arraylist<>();
        basicnamevaluepair pair1 = new basicnamevaluepair("a", "aaa");
        basicnamevaluepair pair2 = new basicnamevaluepair("b", "bbb");
        list.add(pair1);
        list.add(pair2);
        urlencodedformentity urlencodedformentity = new urlencodedformentity(list,"utf-8");
        post.setentity(urlencodedformentity);
        string boundary = new uuidgenerator().next();
        // 设置请求格式 multipart/form-data
        post.addheader("content-type", "multipart/form-data;boundary=" + boundary);
        post.addheader("accept", "*/*");
        // utf-8 解决中文乱码
        post.addheader("accept-encoding", "utf-8");
        post.addheader("user-agent", " mozilla/5.0 (windows nt 10.0; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/123.0.0.0 safari/537.36");
        // 发送 post 请求
        httpresponse response = httpclient.execute(post);
        ...省略代码
}

上面的代码使用了 urlencodedformentity,basicnamevaluepair 去设置请求格式 multipart/form-data，虽然在 content-type中设置了 boundary，请求还是报请求参数错误：missingservletrequestparameterexception
是因为并没有在 multipart/form-data 的请求数据前后设置分割边界符

【正确】使用 multipartentitybuilder 构造 boundary

要使用multipartentitybuilder，先引入maven

<dependency>
    <groupid>org.apache.httpcomponents</groupid>
    <artifactid>httpclient</artifactid>
    <version>4.5</version>
</dependency>
<dependency>
    <groupid>org.apache.httpcomponents</groupid>
    <artifactid>httpmime</artifactid>
    <version>4.5</version>
</dependency>

java用httpclient（apache）完整的纯文本form-data请求实现如下：

public enum test {
    ;
    private static final logger logger = loggerfactory.getlogger(test.class);
    /**
     * setconnecttimeout: 从客户端到url建立连接的超时时间
     */
    private static final int connect_timeout = 30 * 1000;
    /**
     * setsockettimeout: 连接上一个url后，获取response的返回等待时间
     */
    private static final int socket_timeout = 3600 * 1000;
    public static jsonobject posthttpformdatapair(string url, jsonobject requestbodyjson, map<string, string> headersmap, string... saverespheadername) {
        requestconfig requestconfig = requestconfig.custom()
                .setconnecttimeout(connect_timeout)
                .setsockettimeout(socket_timeout)
                .setcookiespec(cookiespecs.default)
                .build();
        cookiestore cookiestore = new basiccookiestore();
        // 默认是 closeablehttpclient httpclient = httpclientbuilder.create().build();
        try (closeablehttpclient httpclient = createsslclientdefaultbuilder()
                .setdefaultrequestconfig(requestconfig)
                .setdefaultcookiestore(cookiestore)
                .build()) {
            httppost post = new httppost(url);
            // [重要]:生成边界分隔符 boundary
            string boundary = new uuidgenerator().next();
            // [重要]:设置请求格式 multipart/form-data
            post.addheader("content-type", "multipart/form-data; charset=utf-8; boundary=" + boundary);
            post.addheader("accept", "*/*");
            post.addheader("accept-encoding", "utf-8");
            post.addheader("user-agent", " mozilla/5.0 (windows nt 10.0; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/123.0.0.0 safari/537.36");
            if (!collectionutils.isempty(headersmap)) {
                for (map.entry<string, string> entry : headersmap.entryset()) {
                    post.addheader(entry.getkey(), entry.getvalue());
                }
            }
            // 构造 formdata 请求数据
            multipartentitybuilder multipartentitybuilder = multipartentitybuilder.create()
                    .setcharset(standardcharsets.utf_8)
                    // [重要]:设置 setboundary 边界分隔符
                    .setboundary(boundary);
            multipartentitybuilder.addtextbody("a", "aaa");
            multipartentitybuilder.addtextbody("b", "bbb");
            httpentity postformdatabody = multipartentitybuilder.build();
            // 请求参数
            post.setentity(postformdatabody);
            // 发送 post 请求
            httpresponse response = httpclient.execute(post);
            if (response == null) {
                throw new runtimeexception("response is null");
            } else if (response.getstatusline().getstatuscode() == httpstatus.sc_ok) {
                return getresponsejsonobject(response, saverespheadername);
            } else {
                logger.warn("response status is not 200");
                return getresponsejsonobject(response, saverespheadername);
            }
        } catch (exception ex) {
            logger.error("error:", ex);
            throw new runtimeexception("系统异常");
        }
    }
    @notnull
    private static jsonobject getresponsejsonobject(httpresponse response, string[] saverespheadername) throws ioexception {
        inputstream in = response.getentity().getcontent();
        bufferedreader reader = new bufferedreader(new inputstreamreader(in));
        string lines;
        stringbuilder responsemsg = new stringbuilder("");
        while ((lines = reader.readline()) != null) {
            lines = new string(lines.getbytes(), standardcharsets.utf_8);
            responsemsg.append(lines);
        }
        reader.close();
        in.close();
        jsonobject jsonobject = new jsonobject();
        jsonobject.put("message", responsemsg.tostring());
        // save header
        for (string name : saverespheadername) {
            jsonobject.put(name, response.getheaders(name));
        }
        return jsonobject;
    }
    /**
     * 绕过https证书校验
     */
    public static httpclientbuilder createsslclientdefaultbuilder() {
        httpclientbuilder httpclientbuilder = null;
        try {
            sslcontextbuilder builder = new sslcontextbuilder();
            // 实现该接口，证书受信任的x509证书校验为true
            builder.loadtrustmaterial(null, (chain, authtype) -> true);
            // 创建httpsurlconnection对象，并设置其sslsocketfactory对象
            sslconnectionsocketfactory socketfactory = new sslconnectionsocketfactory(builder.build(), new string[]{"tlsv1.2"}, null, noophostnameverifier.instance);
            //  httpsurlconnection对象就可以正常连接https了，无论其证书是否经权威机构的验证，只要实现了接口x509trustmanager的类myx509trustmanager信任该证书。
            httpclientbuilder = httpclients.custom().setsslsocketfactory(socketfactory);
        } catch (exception e) {
            e.printstacktrace();
            throw new runtimeexception("系统异常");
        }
        return httpclientbuilder;
    }
}

总结

想要代码实现 form-data格式的请求要注意下面2点：

设置 boundary 边界分隔符