fix missing class constructor (mostly GSon serialized classes)

server/sonar-auth-gitlab/src/main/java/org/sonar/auth/gitlab/GsonUser.java

@@ -30,6 +30,12 @@ public class GsonUser {
   private String name;
   private String email;
 
+  public GsonUser() {
+    // even if empty constructor is not required for Gson, it is strongly
+    // recommended:
+    // http://stackoverflow.com/a/18645370/229031
+  }
+
   public long getId() {
     return id;
   }

server/sonar-ce-task-projectanalysis/src/main/java/org/sonar/ce/task/projectanalysis/api/measurecomputer/MeasureComputerDefinitionImpl.java

@@ -84,7 +84,7 @@ public class MeasureComputerDefinitionImpl implements MeasureComputer.MeasureCom
 
     private String[] inputMetricKeys = new String[] {};
     @CheckForNull
-    private String[] outputMetrics;
+    private String[] outputMetrics = null;
 
     @Override
     public Builder setInputMetrics(String... inputMetrics) {

server/sonar-ce-task-projectanalysis/src/main/java/org/sonar/ce/task/projectanalysis/batch/BatchReportDirectoryHolderImpl.java

@@ -24,7 +24,7 @@ import java.util.Objects;
 
 public class BatchReportDirectoryHolderImpl implements MutableBatchReportDirectoryHolder {
 
-  private File directory;
+  private File directory = null;
 
   @Override
   public void setDirectory(File newDirectory) {

server/sonar-ce-task-projectanalysis/src/main/java/org/sonar/ce/task/projectanalysis/component/ComponentTreeBuilder.java

@@ -351,7 +351,7 @@ public class ComponentTreeBuilder {
 
   private static class Node {
     private final Map<String, Node> children = new LinkedHashMap<>();
-    private ScannerReport.Component reportComponent;
+    private ScannerReport.Component reportComponent = null;
 
     private Map<String, Node> children() {
       return children;

server/sonar-ce-task-projectanalysis/src/main/java/org/sonar/ce/task/projectanalysis/component/DisabledComponentsHolderImpl.java

@@ -25,7 +25,7 @@ import static com.google.common.base.Preconditions.checkState;
 
 public class DisabledComponentsHolderImpl implements MutableDisabledComponentsHolder {
 
-  private Set<String> uuids;
+  private Set<String> uuids = null;
 
   @Override
   public Set<String> getUuids() {

server/sonar-ce-task-projectanalysis/src/main/java/org/sonar/ce/task/projectanalysis/component/TreeRootHolderImpl.java

@@ -33,14 +33,12 @@ import static org.sonar.ce.task.projectanalysis.component.ComponentVisitor.Order
  */
 public class TreeRootHolderImpl implements MutableTreeRootHolder {
   @CheckForNull
-  private Map<Integer, Component> componentsByRef;
-
+  private Map<Integer, Component> componentsByRef = null;
   @CheckForNull
-  private Map<Integer, Component> extendedComponentsByRef;
-
-  private int size;
-  private Component root;
-  private Component extendedTreeRoot;
+  private Map<Integer, Component> extendedComponentsByRef = null;
+  private int size = 0;
+  private Component root = null;
+  private Component extendedTreeRoot = null;
 
   @Override
   public boolean isEmpty() {

server/sonar-ce-task-projectanalysis/src/main/java/org/sonar/ce/task/projectanalysis/filesystem/ComputationTempFolderProvider.java

@@ -38,7 +38,7 @@ import org.sonar.server.platform.ServerFileSystem;
 public class ComputationTempFolderProvider extends ProviderAdapter implements ComponentLifecycle<TempFolder> {
   private boolean started = false;
   @CheckForNull
-  private DefaultTempFolder tempFolder;
+  private DefaultTempFolder tempFolder = null;
 
   public TempFolder provide(ServerFileSystem fs) {
     if (this.tempFolder == null) {

server/sonar-db-dao/src/main/java/org/sonar/db/newcodeperiod/NewCodePeriodDto.java

@@ -22,13 +22,13 @@ package org.sonar.db.newcodeperiod;
 import javax.annotation.CheckForNull;
 
 public class NewCodePeriodDto {
-  private String uuid;
-  private String projectUuid;
-  private String branchUuid;
-  private NewCodePeriodType type;
-  private String value;
-  private long updatedAt;
-  private long createdAt;
+  private String uuid = null;
+  private String projectUuid = null;
+  private String branchUuid = null;
+  private NewCodePeriodType type = null;
+  private String value = null;
+  private long updatedAt = 0L;
+  private long createdAt = 0L;
 
   public static NewCodePeriodDto defaultInstance() {
     return new NewCodePeriodDto().setType(NewCodePeriodType.PREVIOUS_VERSION);

sonar-plugin-api-impl/src/main/java/org/sonar/api/impl/server/RulesDefinitionContext.java

@@ -36,7 +36,7 @@ import static org.sonar.api.utils.Preconditions.checkState;
 
 public class RulesDefinitionContext extends RulesDefinition.Context {
   private final Map<String, RulesDefinition.Repository> repositoriesByKey = new HashMap<>();
-  private String currentPluginKey;
+  private String currentPluginKey = null;
 
   @Override
   public RulesDefinition.NewRepository createRepository(String key, String language) {

sonar-plugin-api/src/main/java/org/sonar/api/server/rule/RulesDefinition.java

@@ -359,7 +359,7 @@ public interface RulesDefinition {
    */
   class Context extends AbstractContext {
     private final Map<String, Repository> repositoriesByKey = new HashMap<>();
-    private String currentPluginKey;
+    private String currentPluginKey = null;
 
     @Override
     public RulesDefinition.NewRepository createRepository(String key, String language) {

sonar-scanner-engine/src/main/java/org/sonar/scanner/bootstrap/ScannerPluginInstaller.java

@@ -112,12 +112,20 @@ public class ScannerPluginInstaller implements PluginInstaller {
 
   private static class InstalledPlugins {
     InstalledPlugin[] plugins;
+
+    public InstalledPlugins() {
+      // http://stackoverflow.com/a/18645370/229031
+    }
   }
 
   static class InstalledPlugin {
     String key;
     String hash;
     long updatedAt;
+
+    public InstalledPlugin() {
+      // http://stackoverflow.com/a/18645370/229031
+    }
   }
 
   private static class Loaded {

sonar-scanner-engine/src/main/java/org/sonar/scanner/externalissue/ReportParser.java

@@ -101,6 +101,10 @@ public class ReportParser {
 
   static class Report {
     Issue[] issues;
+
+    public Report() {
+      // http://stackoverflow.com/a/18645370/229031
+    }
   }
 
   static class Issue {
@@ -113,6 +117,10 @@ public class ReportParser {
     Location primaryLocation;
     @Nullable
     Location[] secondaryLocations;
+
+    public Issue() {
+      // http://stackoverflow.com/a/18645370/229031
+    }
   }
 
   static class Location {
@@ -121,6 +129,10 @@ public class ReportParser {
     String filePath;
     @Nullable
     TextRange textRange;
+
+    public Location() {
+      // http://stackoverflow.com/a/18645370/229031
+    }
   }
 
   static class TextRange {
@@ -131,5 +143,9 @@ public class ReportParser {
     Integer endLine;
     @Nullable
     Integer endColumn;
+
+    public TextRange() {
+      // http://stackoverflow.com/a/18645370/229031
+    }
   }
 }

sonar-scanner-engine/src/main/java/org/sonar/scanner/repository/DefaultMetricsRepositoryLoader.java

@@ -123,6 +123,10 @@ public class DefaultMetricsRepositoryLoader implements MetricsRepositoryLoader {
 
     private int ps;
 
+    public WsMetricsResponse() {
+      // http://stackoverflow.com/a/18645370/229031
+    }
+
     public int getTotal() {
       return total;
     }