HttpServletRequest#getParameter

以Tomcat容器实现为例

实现类为org.apache.catalina.connector.Request

关键代码

1
2
3
4
5
6
7
8
@Override
public String getParameter(String name) {
    // 确保一个Request只会执行一次解析
    if (!parametersParsed) {
        parseParameters();
    }
    ····
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
protected void parseParameters() {
    try {
      	// 处理URL拼接的请求参数
      	parameters.handleQueryParameters();

        if (usingInputStream || usingReader) {
            success = true;
            return;
        }
       	// 获取ContentType 如果有多个取第一个为准
        String contentType = getContentType();
        if (contentType == null) {
            contentType = "";
        }
        int semicolon = contentType.indexOf(';');
        if (semicolon >= 0) {
            contentType = contentType.substring(0, semicolon).trim();
        } else {
            contentType = contentType.trim();
        }
      	// 判断ContentType类型 如果是多媒体类型 那么使用ParseParts
        if ("multipart/form-data".equals(contentType)) {
            parseParts(false);
            success = true;
            return;
        }
      	// 判断是否是需要解析请求体的请求 POST
        if( !getConnector().isParseBodyMethod(getMethod()) ) {
            success = true;
            return;
        }
      	// 当contenttype不为application/x-www-form-urlencoded退出，不在执行下面的关键代码
        if (!("application/x-www-form-urlencoded".equals(contentType))) {
            success = true;
            return;
        }

        int len = getContentLength();

        if (len > 0) {
            int maxPostSize = connector.getMaxPostSize();
            if ((maxPostSize >= 0) && (len > maxPostSize)) {
                Context context = getContext();
                if (context != null && context.getLogger().isDebugEnabled()) {
                    context.getLogger().debug(
                            sm.getString("coyoteRequest.postTooLarge"));
                }
                checkSwallowInput();
                parameters.setParseFailedReason(FailReason.POST_TOO_LARGE);
                return;
            }
            byte[] formData = null;
            if (len < CACHED_POST_LEN) {
                if (postData == null) {
                    postData = new byte[CACHED_POST_LEN];
                }
                formData = postData;
            } else {
                formData = new byte[len];
            }
            try {
                // readPostBody方法其实就是request.getinputstream().read(); 所以getParameter会读取完流,如果需要流多次读取那么需要使用包装类
                if (readPostBody(formData, len) != len) {
                    parameters.setParseFailedReason(FailReason.REQUEST_BODY_INCOMPLETE);
                    return;
                }
            } catch (IOException e) {
                // Client disconnect
                Context context = getContext();
                if (context != null && context.getLogger().isDebugEnabled()) {
                    context.getLogger().debug(
                            sm.getString("coyoteRequest.parseParameters"), e);
                }
                parameters.setParseFailedReason(FailReason.CLIENT_DISCONNECT);
                return;
            }
            parameters.processParameters(formData, 0, len);
        } else if ("chunked".equalsIgnoreCase(
                coyoteRequest.getHeader("transfer-encoding"))) {
            byte[] formData = null;
            try {
                formData = readChunkedPostBody();
            } catch (IllegalStateException ise) {
                // chunkedPostTooLarge error
                parameters.setParseFailedReason(FailReason.POST_TOO_LARGE);
                Context context = getContext();
                if (context != null && context.getLogger().isDebugEnabled()) {
                    context.getLogger().debug(
                            sm.getString("coyoteRequest.parseParameters"),
                            ise);
                }
                return;
            } catch (IOException e) {
                // Client disconnect
                parameters.setParseFailedReason(FailReason.CLIENT_DISCONNECT);
                Context context = getContext();
                if (context != null && context.getLogger().isDebugEnabled()) {
                    context.getLogger().debug(
                            sm.getString("coyoteRequest.parseParameters"), e);
                }
                return;
            }
            if (formData != null) {
                parameters.processParameters(formData, 0, formData.length);
            }
        }
        success = true;
    } finally {
        if (!success) {
            parameters.setParseFailedReason(FailReason.UNKNOWN);
        }
    }
}