opencms 安装细节探讨
引入：
因为项目需求，我们要用到openCMS。虽然以前用过很多类似的内容管理系统类似Vignette,Fatwire,但是openCMS虽然大体功能差不多，具体并没用过，所以这里做了一些研究，会陆续把这些研究心得分享出来。这里先从openCMS安装讲起，虽然简单，但也有一些值得探讨的问题。
安装亮点1：不可以重复配置openCMS。
我们知道，第一次运行openCMS需要做配置，配置的请求URL是：http://localhost:8080/opencms/setup/ ，但是运行第一次之后就不可以运行第二次了，理由是在安装过程中，它会去调用CmsSetupBean类的prepareSetup10()方法：
/**
* Prepares step 10 of the setup wizard.<p>
*/
publicvoidprepareStep10() {
if (isInitialized()) {
// lock the wizard for further use
lockWizard();
// save Properties to file "opencms.properties"
saveProperties(getProperties(),CmsSystemInfo.FILE_PROPERTIES, false);
setSchemaGeneration(false);
m_peristenceConfigurator.save();
}
}
而这个方法会去调用lockWizard()方法后保存opencms.properties让其生效，lockWizard方法的实现就是把opencms.properties中key为wizard.enabled设为false:
publicvoidlockWizard() {
setExtProperty("wizard.enabled", CmsStringUtil.FALSE);
}
这会导致我们的opencms.properties被更改：
# # Enable/Disable OpenCms Setup Wizard # The wizard sets the flag to false after the setup. # To use the wizard again, reset it manually to true. # By setting no value, wizard can always be used. ################################################################################# wizard.enabled=false
而下次运行时候，它会去判断此属性，判断点在CmsAutoSetup类的main()方法中调用的run()方法的第一行：
/**
* Performs the setup.<p>
* @throws Exception
*/
publicvoidrun() throwsException {
if (m_bean.getWizardEnabled()) {
longtimeStarted = System.currentTimeMillis();
CmsSetupTests setupTests = new CmsSetupTests();
…
}
}
安装亮点2： 正确设置max_allowed_packet这个mysql系统变量的大小。
在opencms安装过程中，它会对一些DB变量做检查，其代码如下：
/**
* Returns an optional warning message ifneeded, <code>null</code> if not.<p>
*
* @param db the selected database key
*
* @return html warning, or <code>null</code> if no warning
*/
publicString checkVariables(String db) {
StringBuffer html = new StringBuffer(512);
if (m_con == null){
return null; // prior error,trying to get a connection
}
Exception exception = null;
if (db.equals("mysql")){
String statement = "SELECT @@max_allowed_packet;";
Statement stmt = null;
ResultSet rs = null;
longmaxAllowedPacket = 0;
try {
stmt = m_con.createStatement();
rs = stmt.executeQuery(statement);
if (rs.next()) {
maxAllowedPacket = rs.getLong(1);
}
} catch (Exception e) {
exception = e;
} finally {
if (stmt != null){
try {
stmt.close();
} catch (SQLException e) {
// ignore
}
}
}
if (exception == null){
intmegabyte = 1024 * 1024;
if (maxAllowedPacket > 0) {
html.append("<p>MySQL system variable <code>'max_allowed_packet'</code>is set to ");
html.append(maxAllowedPacket);
html.append(" Byte (");
html.append((maxAllowedPacket / megabyte) + "MB).</p>\n");
}
html.append("<p>Please note that it will not be possible for OpenCms tohandle files bigger than this value in the VFS.</p>\n");
intrequiredMaxAllowdPacket = 16;
if (maxAllowedPacket < (requiredMaxAllowdPacket * megabyte)){
m_errors.add("<p><b>Your <code>'max_allowed_packet'</code>variable is set to less than "
+ (requiredMaxAllowdPacket* megabyte)
+ " Byte("
+ requiredMaxAllowdPacket
+ "MB).</b></p>\n"
+ "<p>The required value for running OpenCms isat least "
+ requiredMaxAllowdPacket
+ "MB."
+ "Please change your MySQL configuration (in the<code>my.ini</code> or <code>my.cnf</code>file).</p>\n");
}
} else {
html.append("<p><i>OpenCms was not able to detect the value of your<code>'max_allowed_packet'</code>variable.</i></p>\n");
html.append("<p>Please note that it will not be possible for OpenCms tohandle files bigger than this value.</p>\n");
html.append("<p><b>The recommended value for running OpenCms is 16MB,please set it in your MySQL configuration (in your<code>my.ini</code> or <code>my.cnf</code>file).</b></p>\n");
html.append(CmsException.getStackTraceAsString(exception));
}
}
if (html.length() == 0) {
return null;
}
return html.toString();
}
从这里可以看出，对于数据库是mysql的情形，它会先去执行数据库查询读取max_allowed_packet的值，这个变量主要让mysql限制服务器接受的单个数据包的大小（因为在openCMS中，经常要存富文本内容，所以这个值还是要设置大点为好），并且如果它<16MB, 则报错our max_allowed_packet variable is set to less than 16MB。而默认的mysql这个值配置是4MB，所以第一次setup出错。我们在my.ini中将其改为30MB,这样才过了这关：
安装亮点3：opencms中资产的存储。
opencms中，这些资产都是以BLOB形式存储的：
