相隔4年多，MIDP终于小心翼翼的升了一小级，从2.0过渡到了2.1.
新版本于20060526发布，拿到新的版本，当然首先要稍微整体把握一下，估计这个月开始新的部门的实装和新老式样的调整也要尽快的展开了。总的来说，这一次新的版本的说明相对于2.0来说，更加容易阅读,比如说排版和小标题号的增加。言归正传，看看究竟有些什么。(转载请注明出处->Yama)

一。简述
1。在文档17面Compliant MIDP2.0 implementation里面加入了
    Must support ISO/IEC JPEG together with JFIF(JPEG File Interchange Format).
    也就是以前没有支持JPEG关联图像格式的厂商这次郁闷了，还是要加上的说。
    另外，2.1的文档里面大量的地方还是2.0的称呼，估计是文档小组太不好好干活的说
2。文档18页的Package Summary里面javax.microedition.lcdui.game终于从
    User Interface Package里面独立出来自成一家Game Package.
    另外就是Persistence Package的排名飙升到Application Lifecycle之后，不知道是不是对于存储方面MIDP2.1更加重视了。还有就是Sound and Tone Media改名为Sound.

二。Over The Air User Initiated Provisioning Specification

1。文档21页MIDlet Suite Installation里面增加了关于MIDlet Suite安装后直接执行的部分。
    In case of user-initiated OTA provisioning, after a MIDlet suite is successfully installed on the device and if the suite contains any MIDlets(that is , one or more MIDlet-<n> attibutes are in the JAD file or JAR manifest), an implementation must prompt the user to specify whether to launch a MIDlet from the suite.if the user approves launching a MIDlet and the MIDlet suite contains only one MIDlet, that specific MIDlet must be launched. If the suite contains several MIDlets, an implementation must give the user the opportunity to choose which MIDlet to launch. After the selection, the chosen MIDlet Must be launched. These requirements apply only to MIDlets that are listed in the JAD file or in the JAR manifest by means of MIDlet-<n> attributes.
    说穿了，也就是加入了直接执行的部分说明。2.0的时候好像什么相关文档中提到过，这个部分应该大多数实现厂商都提供了。所以虽然是新加的，但是也不用从新对应了。

2。Page23 MIDlet Suite Removal
    在MIDP2.0里面关于包含复数MIDlet的MIDlet Suite的删除时候the MIDlet suite may contain multiple MIDlets,and the user should be made aware that all of the MIDlets and associated RMS record stores are being removed. 而MIDP2.1里面该段话变成了强制执行-〉if a MIDlet suite contains multiple MIDlets, an implementation must make the user aware of the MIDlets and associated RMS record stores that will be removed, and the user must be given the chance to abort this action.

3。Page24 Installation/Deletion status reports
    For installations里面关于状态发送的部分有了很大的改动，主要是强制说明了最少必须重发5次。
    MIDP2.0里面，for installations, if the status report cannot be sent, or if the server reply is not received, the installation status report may be sent again(as described above)each time a MIDlet in this suite is executed and the device has data network connectivity.
    而MIDP2.1里面说这种情况下，an implementation must attempt to resend the report at least 5 times.并且，attempts to resend the status report must not be performed after a response from the server is received.

    同样的for deletions和安装完全一样，也需要最少重发5次，并且一旦受到服务器的应答后就必须停止重发了。但是重发的条件有点奇怪？if the status report cannot be sent, or if the server reply is not received.也就是说安装后没有发送的时候如果关机的话，按照现在的文档来说是必须要重发的，这样的话这部如何处理。以后在什么时候重发，需要和delete的状态报告一样方式处理么？
   
三。Security for MIDP Applications
四。Trusted MIDlet Suites using X.509 PKI

...
5.java.lang
6.java.util
7.javax.microedition.io
8.javax.microedition.lcdui
9.javax.microedition.lcdui.game
10.javax.microedition.media
11.javax.microedition.media.control

十二。javax.microedition.midlet
１．P427－４２８MIDlet-<n>属性说明里面关于icon的描述里面增加了以下的东东。
    If an implementation displays MIDlet icons(using associated MIDlet-Icon attribute), the following requirement apply:
    1> The application manager must always be able to display a MIDlet-Icon of 16 by 16 pixels in the application list
    2>The application manager should always be able to display a MIDlet-Icon of 24 by 24 pixels in the application list
    3>A MIDlet-Icon larger than 24 by 24 may be displayed properly in full size in the application list
    4>A MIDlet-Icon must not be scaled down in the application list, but the application manager may use centered cropping to fit the icon into the list.

２．MicroEdition-Profile没有详细的特别说明,但是midp2.1的话这个部分是不是有变更的必要性呢？要调查！！！

３．P429 新的属性增加 Runtime-Execution-Environment
    This is an optional attribute that indicates the runtime execution environment REQUIRED by the application. This attribute MAY have the value MIDP.CLDC. If the MIDlet suite does not specify the attribute, the implicit value is MIDP.CLDC. When the value of the Runtime-Execution-Environment attribute is MIDP.CLDC, the behavior of the implementation MUST adhere to the requirements presented in the following more detailed
description. Additional values for this attribute MAY be defined in future
    后面并且为此加入了12.2.3.1大段说明
    When an application defines the Runtime-Execution-Environment attribute value MIDP.CLDC or does not define this attribute, the behavior of the mobile handset implementation during execution of this application MUST adhere to the following requirements:
    • The set of supported APIs and the API behavior, as well as the behavior of the underlying virtual machine, MUST comply with the CLDC 1.1 specification.
    • A mobile handset implementation MAY alternatively use the CDC configuration of Java ME. However, if CDC is used as the underlying configuration, applications running on top of this platform MUST see an enviroment that is semantically and functionally equivalent to a CLDC 1.1 platform. CDC-specific APIs or CDC-specfic behavior MUST NOT be exposed to applications or application developers.
    • When an application defines the Runtime-Execution-Environment attribute value MIDP.CLDC the application MUST also define a CLDC platform in the MicroEdition-Configuration attribute. If this is not the case, the application MUST NOT be installed and Status Code 905 "Attribute Mismatch" MUST be used when reporting the installation suite.
    • If an application defines a value for the Runtime-Execution-Environment or MicroEdition-Configuration attribute that is not supported by the implementation, the application MUST NOT be installed. All mobile handset implementations MUST support the "MIDP.CLDC" value for the Runtime-Execution-Environment attribute.
    • A mobile handset implementation MUST support the Runtime-Execution-Environment attribute.

４．P430 An attribute MUST not appear more than once within the manifest. If an attribute is　duplicated the effect is unspecified
    2.0和2.1是一样的,但是好像现在我的实现错掉了,为了防止忘记,顺便记下

５．P431 加入的这部门仅仅说明下面3个属性的重要性有所增加,但是对于实装来说没有什么很大的影响
    In addition, to improve the user experience (by rejecting incompatible suites without needing to download the JAR file), the application descriptor SHOULD contain the following attributes:
    • MicroEdition-Profile
    • MicroEdition-Configuration
    • MIDlet-Permissions

６．P432
７．


...
13.javax.microedition.pki
14.javax.microedition.rms
15.The Recommended Security Policy for GSM/UMTS Compliant Devices