接上一篇 15. Gradle編譯其他應用代碼流程（四) - Configure過程 繼續分析
一. task選擇
到了這個階段，gradle開始計算task入口是哪個？ 選擇的邏輯是這樣：
如果用戶收入了task，比如這樣的指令'gradle pmd'，那麼就執行pmd這個task
如果用戶沒有輸入task，比如直接輸入'gradle'，那麼看有沒有默認的task
如果沒有默認的task，那就執行help這個task。大家可以試下直接輸入gradle，看看輸出什麼內容。
接下來看源代碼。
文件路徑：subprojects\core\src\main\java\org\gradle\initialization\DefaultGradleLauncher.java
private void doBuildStages(Stage upTo) {
...
// After this point, the GradleLauncher cannot be reused
stage = Stage.Build;
// Populate task graph
buildOperationExecutor.run("Calculate task graph", new Runnable() {
@Override
public void run() {
buildConfigurationActionExecuter.select(gradle);
if (gradle.getStartParameter().isConfigureOnDemand()) {
buildListener.projectsEvaluated(gradle);
}
}
});
...
}文件路徑：
subprojects\core\src\main\java\org\gradle\execution\DefaultBuildConfigurationActionExecuter.java
public class DefaultBuildConfigurationActionExecuter implements BuildConfigurationActionExecuter {
...
public void select(GradleInternal gradle) {
List<BuildConfigurationAction> processingBuildActions = CollectionUtils.flattenCollections(BuildConfigurationAction.class, configurationActions, taskSelectors);
configure(processingBuildActions, gradle, 0);
}
...
private void configure(final List<BuildConfigurationAction> processingConfigurationActions, final GradleInternal gradle, final int index) {
if (index >= processingConfigurationActions.size()) {
return;
}
BuildConfigurationAction action = processingConfigurationActions.get(index);
System.out.println("DefaultBuildConfigurationActionExecuter action: " + action + " index: " + index);
/*processingConfigurationActions.get(index)*/action.configure(new BuildExecutionContext() {
public GradleInternal getGradle() {
return gradle;
}
public void proceed() {
configure(processingConfigurationActions, gradle, index + 1);
}
});
}
}這個地方的寫法挺奇怪的，它的想法是遍歷processingConfigurationActions裏面的每個action，然後執行它的configure方法，所以它用了遞歸。
但是個人覺得直接用循環不是更簡單直接嗎？
先不去管這些，processingConfigurationActions裏面有3個成員，他們繼承自同一接口BuildConfigurationAction。
org.gradle.execution.ExcludedTaskFilteringBuildConfigurationAction@3ee68eb2 index: 0 org.gradle.execution.DefaultTasksBuildExecutionAction@49cd08f9 index: 1 org.gradle.execution.TaskNameResolvingBuildConfigurationAction@4eace42b index: 2
他們3個分別處理的事情不一樣。
a. ExcludedTaskFilteringBuildConfigurationAction用來處理不執行的task，如果用戶有配置的話。
代碼如下：
文件路徑：
subprojects\core\src\main\java\org\gradle\execution\ExcludedTaskFilteringBuildConfigurationAction.java
/**
* A {@link BuildConfigurationAction} which filters excluded tasks.
*/
public class ExcludedTaskFilteringBuildConfigurationAction implements BuildConfigurationAction {
...
public void configure(BuildExecutionContext context) {
GradleInternal gradle = context.getGradle();
Set<String> excludedTaskNames = gradle.getStartParameter().getExcludedTaskNames();
if (!excludedTaskNames.isEmpty()) {
final Set<Spec<Task>> filters = new HashSet<Spec<Task>>();
for (String taskName : excludedTaskNames) {
filters.add(taskSelector.getFilter(taskName));
}
gradle.getTaskGraph().useFilter(Specs.intersect(filters));
}
context.proceed();
}
}b. DefaultTasksBuildExecutionAction用來處理默認的task，如果用戶有輸入task，那麼就使用用戶輸入的。比如用戶輸入'gradle pmd'，那麼使用的task就是pmd
如果用戶沒有輸入task，那麼就使用默認的task
如果默認task也沒有，則使用help task，比如用戶直接輸入'gradle'
文件路徑：
subprojects\core\src\main\java\org\gradle\execution\DefaultTasksBuildExecutionAction.java
public class DefaultTasksBuildExecutionAction implements BuildConfigurationAction {
...
public void configure(BuildExecutionContext context) {
StartParameter startParameter = context.getGradle().getStartParameter();
System.out.println("DefaultTasksBuildExecutionAction configure. startParameter: " + startParameter);
//判斷是否有輸入task?
for (TaskExecutionRequest request : startParameter.getTaskRequests()) {
if (!request.getArgs().isEmpty()) {
context.proceed();
return;
}
}
//沒有輸入task，嘗試使用默認task和help task
// Gather the default tasks from this first group project
ProjectInternal project = context.getGradle().getDefaultProject();
//so that we don't miss out default tasks
projectConfigurer.configure(project);
List<String> defaultTasks = project.getDefaultTasks();
if (defaultTasks.size() == 0) {
defaultTasks = Collections.singletonList(ProjectInternal.HELP_TASK);
LOGGER.info("No tasks specified. Using default task {}", GUtil.toString(defaultTasks));
System.out.println("No tasks specified. Using default task {}" + "-" + GUtil.toString(defaultTasks));
} else {
LOGGER.info("No tasks specified. Using project default tasks {}", GUtil.toString(defaultTasks));
System.out.println("No tasks specified. Using project default tasks {}" + " - " + GUtil.toString(defaultTasks));
}
startParameter.setTaskNames(defaultTasks);
context.proceed();
}
}c. TaskNameResolvingBuildConfigurationAction
把輸入的task(如果沒有輸入，則使用默認task或者 help)添加到executer裏面，爲真正執行做準備。
代碼路徑：
subprojects\core\src\main\java\org\gradle\execution\TaskNameResolvingBuildConfigurationAction.java
/**
* A {@link BuildConfigurationAction} which selects tasks which match the provided names. For each name, selects all tasks in all
* projects whose name is the given name.
*/
public class TaskNameResolvingBuildConfigurationAction implements BuildConfigurationAction {
...
public void configure(BuildExecutionContext context) {
System.out.println("TaskNameResolvingBuildConfigurationAction configure 1");
GradleInternal gradle = context.getGradle();
TaskGraphExecuter executer = gradle.getTaskGraph();
List<TaskExecutionRequest> taskParameters = gradle.getStartParameter().getTaskRequests();
for (TaskExecutionRequest taskParameter : taskParameters) {
System.out.println("TaskNameResolvingBuildConfigurationAction configure 2");
List<TaskSelector.TaskSelection> taskSelections = commandLineTaskParser.parseTasks(taskParameter);
for (TaskSelector.TaskSelection taskSelection : taskSelections) {
LOGGER.info("Selected primary task '{}' from project {}", taskSelection.getTaskName(), taskSelection.getProjectPath());
System.out.println("Selected primary task '{}' from project {}" + taskSelection.getTaskName() + "-"+ taskSelection.getProjectPath());
executer.addTasks(taskSelection.getTasks());
}
}
context.proceed();
}
}二. 通知projectsEvaluated
if (gradle.getStartParameter().isConfigureOnDemand()) {
buildListener.projectsEvaluated(gradle);
}到此爲止，所有的準備工作都已經做好了，接下就要真正的執行這個task了。
配置文件加載
gradle文件加載以及相應的plugin 類加載
要執行的task選擇
下一篇帖子講task的執行。