上文写到Solr的启动过程是在SolrDispatchFilter的init()里实现，当Tomcat启动时候会自动调用init();
Solr的启动主要在 this.cores = createCoreContainer();语句中实现。
/**
*初始化，当tomcat启动时候开始初始化，其中主要调用createCoreContainer来实现Solr的初始化
*/
public void init(FilterConfig config) throws ServletException
{
log.info("SolrDispatchFilter.init()");
try {
// web.xml configuration
this.pathPrefix = config.getInitParameter( "path-prefix" );
this.cores = createCoreContainer();
log.info("user.dir=" + System.getProperty("user.dir"));
}
catch( Throwable t ) {
// catch this so our filter still works
log.error( "Could not start Solr. Check solr/home property and the logs");
SolrCore.log( t );
if (t instanceof Error) {
throw (Error) t;
}
}
log.info("SolrDispatchFilter.init() done");
}
Solr的启动过程主要包括：
1、 获取SolrHome：分别先后通过JNDI，Systemproperty，defaultdirectory三种方式尝试获取；
2、 实例化启动过程中使用的类加载器SolrResourceLoader；
3、 加载solrhome下的solr.xml文件，封装为ConfigSolr；
4、 实例化一个CoreContainer,通过CoreContainer来加载cores；
5、 遍历SolrHome，当寻找到含有core.properties的文件夹，则作为一个core；
6、 多线程加载cores；
7、 加载每个core时先加载solrconfig.xml封装为SolrConfig；
8、 再加载schema.xml封装为IndexSchema；
9、 最后实例化SolrCore；
以下是createCoreContainer()实现代码，该函数就包含了以上的启动过程。
1 /**
2 * Override this to change CoreContainer initialization
3 * @return a CoreContainer to hold this server's cores
4 */
5 protected CoreContainer createCoreContainer() {
6 SolrResourceLoader loader = new SolrResourceLoader(SolrResourceLoader.locateSolrHome());
7 ConfigSolr config = loadConfigSolr(loader);
8 CoreContainer cores = new CoreContainer(loader, config);
9 cores.load();
10 return cores;
11 }
1、 获取SolrHome信息；
Solr通过三种方式来获取SolrHome,分别是JNDI,System property,以及当前路径。
JNDI的java:comp/env/solr/home的获取，主要通过在tomcat/conf/Catalina/localhost目录下新建solr.xml。Tomcat启动的时候就会该目录下自动获取 SolrHome的信息.
System property的SolrHome获取是直接在tomcat启动脚本catalina.sh中加入set JAVA_OPTS -Dsolr.solr.home=/Users/rcf/workspace/java/solr 。
最后的获取SolrHome的方式就是在当前目录下查找。
1 /**
2 * Determines the solrhome from the environment.
3 * Tries JNDI (java:comp/env/solr/home) then system property (solr.solr.home);
4 * if both fail, defaults to solr/
5 * @return the instance directory name
6 */
7 /**
8 * Finds the solrhome based on looking up the value in one of three places:
9 * <ol>
10 * <li>JNDI: via java:comp/env/solr/home</li>
11 * <li>The system property solr.solr.home</li>
12 * <li>Look in the current working directory for a solr/ directory</li>
13 * </ol>
14 *
15 * The return value is normalized. Normalization essentially means it ends in a trailing slash.
16 * @return A normalized solrhome
17 * @see #normalizeDir(String)
18 */
19 public static String locateSolrHome() {
20
21 String home = null;
22 // Try JNDI
23 try {
24 Context c = new InitialContext();
25 home = (String)c.lookup("java:comp/env/"+project+"/home");
26 log.info("Using JNDI solr.home: "+home );
27 } catch (NoInitialContextException e) {
28 log.info("JNDI not configured for "+project+" (NoInitialContextEx)");
29 } catch (NamingException e) {
30 log.info("No /"+project+"/home in JNDI");
31 } catch( RuntimeException ex ) {
32 log.warn("Odd RuntimeException while testing for JNDI: " + ex.getMessage());
33 }
34
35 // Now try system property
36 if( home == null ) {
37 String prop = project + ".solr.home";
38 home = System.getProperty(prop);
39 if( home != null ) {
40 log.info("using system property "+prop+": " + home );
41 }
42 }
43
44 // if all else fails, try
45 if( home == null ) {
46 home = project + '/';
47 log.info(project + " home defaulted to '" + home + "' (could not find system property or JNDI)");
48 }
49 return normalizeDir( home );
50 }
1 <Context docBase="/Users/rcf/workspace/java/tomcat/apache-tomcat-8.0.9/webapps/solr.war" debug="0" crossContext="true" >
2 <Environment name="solr/home" type="java.lang.String" value="/Users/rcf/workspace/java/solr" override="true" />
3 </Context>
获取完SolrHome后,就会实例化SolrResourceLoader。因为传进去的parent是null，所以parents是ContextClassLoader，并且加载了SolrHome/lib/下的文件.
1 /**
2 * <p>
3 * This loader will delegate to the context classloader when possible,
4 * otherwise it will attempt to resolve resources using any jar files
5 * found in the "lib/" directory in the specified instance directory.
6 * </p>
7 *
8 * @param instanceDir - base directory for this resource loader, if null locateSolrHome() will be used.
9 * @see #locateSolrHome
10 */
11 public SolrResourceLoader( String instanceDir, ClassLoader parent, Properties coreProperties )
12 {
13 if( instanceDir == null ) {
14 this.instanceDir = SolrResourceLoader.locateSolrHome();
15 log.info("new SolrResourceLoader for deduced Solr Home: '{}'",
16 this.instanceDir);
17 } else{
18 this.instanceDir = normalizeDir(instanceDir);
19 log.info("new SolrResourceLoader for directory: '{}'",
20 this.instanceDir);
21 }
22
23 this.classLoader = createClassLoader(null, parent);
24 addToClassLoader("./lib/", null, true);
25 reloadLuceneSPI();
26 this.coreProperties = coreProperties;
27 }
1 /**
2 * Convenience method for getting a new ClassLoader using all files found
3 * in the specified lib directory.
4 */
5 static URLClassLoader createClassLoader(final File libDir, ClassLoader parent) {
6 if ( null == parent ) {
7 parent = Thread.currentThread().getContextClassLoader();
8 }
9 return replaceClassLoader(URLClassLoader.newInstance(new URL[0], parent),
10 libDir, null);
11 }
1 /**
2 * Adds every file/dir found in the baseDir which passes the specified Filter
3 * to the ClassLoader used by this ResourceLoader. This method <b>MUST</b>
4 * only be called prior to using this ResourceLoader to get any resources, otherwise
5 * it's behavior will be non-deterministic. You also have to {link @reloadLuceneSPI}
6 * before using this ResourceLoader.
7 *
8 * <p>This method will quietly ignore missing or non-directory <code>baseDir</code>
9 * folder.
10 *
11 * @param baseDir base directory whose children (either jars or directories of
12 * classes) will be in the classpath, will be resolved relative
13 * the instance dir.
14 * @param filter The filter files must satisfy, if null all files will be accepted.
15 * @param quiet Be quiet if baseDir does not point to a directory or if no file is
16 * left after applying the filter.
17 */
18 void addToClassLoader(final String baseDir, final FileFilter filter, boolean quiet) {
19 File base = FileUtils.resolvePath(new File(getInstanceDir()), baseDir);
20 if (base != null && base.exists() && base.isDirectory()) {
21 File[] files = base.listFiles(filter);
22 if (files == null || files.length == 0) {
23 if (!quiet) {
24 log.warn("No files added to classloader from lib: "
25 + baseDir + " (resolved as: " + base.getAbsolutePath() + ").");
26 }
27 } else {
28 this.classLoader = replaceClassLoader(classLoader, base, filter);
29 }
30 } else {
31 if (!quiet) {
32 log.warn("Can't find (or read) directory to add to classloader: "
33 + baseDir + " (resolved as: " + base.getAbsolutePath() + ").");
34 }
35 }
36 }
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