Guava makes defensive programming more pleasant.

src/main/java/com/samskivert/depot/EHCacheAdapter.java

@@ -39,6 +39,8 @@ import net.sf.ehcache.distribution.RMICacheReplicatorFactory;
 import net.sf.ehcache.event.CacheEventListener;
 import net.sf.ehcache.store.MemoryStoreEvictionPolicy;
 
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
 import static com.samskivert.depot.Log.log;
 
 /**
@@ -149,9 +151,8 @@ public class EHCacheAdapter
     {
         long now = System.currentTimeMillis();
         Ehcache cache = _categories.get(category);
-        if (cache == null) {
+        checkArgument(cache != null, "Unknown category: " + category);
-            throw new IllegalArgumentException("Unknown category: " + category);
+
-        }
         @SuppressWarnings("unchecked")
         EHCacheBin<T> bin = (EHCacheBin<T>) _bins.get(cacheId);
         if (bin == null) {
@@ -305,9 +306,8 @@ public class EHCacheAdapter
     {
         public EHCacheKey (String id, Serializable key)
         {
-            if (id == null || key == null) {
+            checkNotNull(id);
-                throw new IllegalArgumentException("Can't handle null key or id");
+            checkNotNull(key);
-            }
             _id = id;
             _key = key;
         }

src/main/java/com/samskivert/depot/Key.java

@@ -37,6 +37,8 @@ import com.samskivert.depot.impl.DepotMarshaller;
 import com.samskivert.depot.impl.DepotUtil;
 import com.samskivert.depot.impl.FragmentVisitor;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 /**
  * A special form of {@link WhereClause} that uniquely specifies a single database row and thus
  * also a single persistent object. It knows how to invalidate itself upon modification. This class
@@ -181,12 +183,9 @@ public class Key<T extends PersistentRecord> extends WhereClause
     // from ValidatingCacheInvalidator
     public void validateFlushType (Class<?> pClass)
     {
-        if (!pClass.equals(_pClass)) {
+        checkArgument(pClass.equals(_pClass),
-            throw new IllegalArgumentException(
+                      "Class mismatch between persistent record and cache invalidator " +
-                "Class mismatch between persistent record and cache invalidator " +
+                      "[record=%s, invtype=%s].", pClass.getSimpleName(), _pClass.getSimpleName());
-                "[record=" + pClass.getSimpleName() +
-                ", invtype=" + _pClass.getSimpleName() + "].");
-        }
     }
 
     // from CacheInvalidator
@@ -247,9 +246,8 @@ public class Key<T extends PersistentRecord> extends WhereClause
     protected static Comparable<?>[] toCanonicalOrder (
         Class<? extends PersistentRecord> pClass, ColumnExp<?>[] fields, Comparable<?>[] values)
     {
-        if (fields.length != values.length) {
+        checkArgument(fields.length == values.length,
-            throw new IllegalArgumentException("Field and Value arrays must be of equal length.");
+                      "Field and Value arrays must be of equal length.");
-        }
 
         // look up the cached primary key fields for this object
         ColumnExp<?>[] keyFields = DepotUtil.getKeyFields(pClass);
@@ -269,24 +267,16 @@ public class Key<T extends PersistentRecord> extends WhereClause
         Comparable<?>[] cvalues = new Comparable<?>[values.length];
         for (int ii = 0; ii < keyFields.length; ii++) {
             Comparable<?> value = map.remove(keyFields[ii]);
-            if (value == null) {
+            // make sure we were provided with a value for this primary key field
-                // make sure we were provided with a value for this primary key field
+            checkArgument(value != null, "Missing value for key field: " + keyFields[ii]);
-                throw new IllegalArgumentException(
+            checkArgument(value instanceof Serializable,
-                    "Missing value for key field: " + keyFields[ii]);
+                          "Non-serializable argument [key=%s, value=%s]", keyFields[ii], value);
-            }
-            if (!(value instanceof Serializable)) {
-                throw new IllegalArgumentException(
-                    "Non-serializable argument [key=" + keyFields[ii] +
-                    ", value=" + value + "]");
-            }
             cvalues[ii] = value;
         }
 
         // finally make sure we were not given any fields that are not primary key fields
-        if (map.size() > 0) {
+        checkArgument(map.isEmpty(), "Non-key columns given: " +
-            throw new IllegalArgumentException(
+                      StringUtil.join(map.keySet().toArray()));
-                "Non-key columns given: " +  StringUtil.join(map.keySet().toArray(), ", "));
-        }
 
         return cvalues;
     }

src/main/java/com/samskivert/depot/QueryBuilder.java

@@ -32,6 +32,9 @@ import com.samskivert.depot.expression.SQLExpression;
 import com.samskivert.depot.impl.ColumnSet;
 import com.samskivert.depot.impl.FindAllQuery;
 
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkState;
+
 /**
  * The root of a fluent mechanism for constructing queries. Obtain an instance via {@link
  * DepotRepository#from}.
@@ -96,9 +99,7 @@ public class QueryBuilder<T extends PersistentRecord>
     public QueryBuilder<T> where (Iterable<? extends SQLExpression> exprs)
     {
         Iterator<? extends SQLExpression> iter = exprs.iterator();
-        if (!iter.hasNext()) {
+        checkArgument(iter.hasNext(), "Must supply at least one expression.");
-            throw new IllegalArgumentException("Must supply at least one expression.");
-        }
         SQLExpression first = iter.next();
         return where(iter.hasNext() ? new Where(Ops.and(exprs)) : new Where(first));
     }
@@ -128,7 +129,7 @@ public class QueryBuilder<T extends PersistentRecord>
      */
     public QueryBuilder<T> where (WhereClause where)
     {
-        requireNull(_where, "Where clause is already configured.");
+        checkState(_where == null, "Where clause is already configured.");
         _where = where;
         return this;
     }
@@ -177,7 +178,7 @@ public class QueryBuilder<T extends PersistentRecord>
      */
     public QueryBuilder<T> groupBy (SQLExpression... exprs)
     {
-        requireNull(_groupBy, "GroupBy clause is already configured.");
+        checkState(_groupBy == null, "GroupBy clause is already configured.");
         _groupBy = new GroupBy(exprs);
         return this;
     }
@@ -211,7 +212,7 @@ public class QueryBuilder<T extends PersistentRecord>
      */
     public QueryBuilder<T> orderBy (OrderBy orderBy)
     {
-        requireNull(_orderBy, "OrderBy clause is already configured.");
+        checkState(_orderBy == null, "OrderBy clause is already configured.");
         _orderBy = orderBy;
         return this;
     }
@@ -221,7 +222,7 @@ public class QueryBuilder<T extends PersistentRecord>
      */
     public QueryBuilder<T> limit (int count)
     {
-        requireNull(_limit, "Limit clause is already configured.");
+        checkState(_limit == null, "Limit clause is already configured.");
         _limit = new Limit(0, count);
         return this;
     }
@@ -231,7 +232,7 @@ public class QueryBuilder<T extends PersistentRecord>
      */
     public QueryBuilder<T> limit (int offset, int count)
     {
-        requireNull(_limit, "Limit clause is already configured.");
+        checkState(_limit == null, "Limit clause is already configured.");
         _limit = new Limit(offset, count);
         return this;
     }
@@ -258,7 +259,7 @@ public class QueryBuilder<T extends PersistentRecord>
      */
     public QueryBuilder<T> override (FromOverride fromOverride)
     {
-        requireNull(_fromOverride, "FromOverride clause is already configured.");
+        checkState(_fromOverride == null, "FromOverride clause is already configured.");
         _fromOverride = fromOverride;
         return this;
     }
@@ -304,7 +305,7 @@ public class QueryBuilder<T extends PersistentRecord>
      */
     public QueryBuilder<T> forUpdate ()
     {
-        requireNull(_forUpdate, "ForUpdate clause is already configured.");
+        checkState(_forUpdate == null, "ForUpdate clause is already configured.");
         _forUpdate = new ForUpdate();
         return this;
     }
@@ -450,30 +451,16 @@ public class QueryBuilder<T extends PersistentRecord>
         }
     }
 
-    protected void requireNotNull (Object value, String message)
-    {
-        if (value == null) {
-            throw new IllegalStateException(message);
-        }
-    }
-
-    protected void requireNull (Object value, String message)
-    {
-        if (value != null) {
-            throw new IllegalStateException(message);
-        }
-    }
-
     protected void assertValidDelete ()
     {
-        requireNotNull(_where, "Where clause must be specified for delete.");
+        checkState(_where != null, "Where clause must be specified for delete.");
-        requireNull(_joins, "Join clauses not supported by delete.");
+        checkState(_joins == null, "Join clauses not supported by delete.");
-        requireNull(_orderBy, "OrderBy clause not applicable for delete.");
+        checkState(_orderBy == null, "OrderBy clause not applicable for delete.");
-        requireNull(_groupBy, "GroupBy clause not applicable for delete.");
+        checkState(_groupBy == null, "GroupBy clause not applicable for delete.");
-        requireNull(_limit, "Limit clause not supported by delete.");
+        checkState(_limit == null, "Limit clause not supported by delete.");
-        requireNull(_fromOverride, "FromOverride clause not applicable for delete.");
+        checkState(_fromOverride == null, "FromOverride clause not applicable for delete.");
-        requireNull(_fieldDefs, "FieldDefinition clauses not applicable for delete.");
+        checkState(_fieldDefs == null, "FieldDefinition clauses not applicable for delete.");
-        requireNull(_forUpdate, "ForUpdate clause not supported by delete.");
+        checkState(_forUpdate == null, "ForUpdate clause not supported by delete.");
     }
 
     protected final PersistenceContext _ctx;

src/main/java/com/samskivert/depot/SchemaMigration.java

@@ -32,6 +32,7 @@ import com.samskivert.depot.expression.ColumnExp;
 import com.samskivert.depot.impl.FieldMarshaller;
 import com.samskivert.depot.impl.Modifier;
 
+import static com.google.common.base.Preconditions.checkArgument;
 import static com.samskivert.depot.Log.log;
 
 /**
@@ -97,25 +98,20 @@ public abstract class SchemaMigration extends Modifier
         @Override
         protected int invoke (Connection conn, DatabaseLiaison liaison) throws SQLException {
             if (!liaison.tableContainsColumn(conn, _tableName, _oldColumnName)) {
-                if (liaison.tableContainsColumn(conn, _tableName, _newColumnName)) {
+                // if the new column already exists, log a warning, otherwise freak out
-                    // we'll accept this inconsistency
+                checkArgument(liaison.tableContainsColumn(conn, _tableName, _newColumnName),
-                    log.warning(_tableName + "." + _oldColumnName + " already renamed to " +
+                              _tableName + " does not contain '" + _oldColumnName + "'");
-                                _newColumnName + ".");
+                log.warning(_tableName + "." + _oldColumnName + " already renamed to " +
-                    return 0;
+                            _newColumnName + ".");
-                }
+                return 0;
-                // but this is not OK
-                throw new IllegalArgumentException(
-                    _tableName + " does not contain '" + _oldColumnName + "'");
             }
 
             // nor is this
-            if (liaison.tableContainsColumn(conn, _tableName, _newColumnName)) {
+            checkArgument(!liaison.tableContainsColumn(conn, _tableName, _newColumnName),
-                throw new IllegalArgumentException(
+                          _tableName + " already contains '" + _newColumnName + "'");
-                    _tableName + " already contains '" + _newColumnName + "'");
-            }
 
             log.info("Renaming '" + _oldColumnName + "' to '" + _newColumnName + "' in: " +
-                _tableName);
+                     _tableName);
             return liaison.renameColumn(
                 conn, _tableName, _oldColumnName, _newColumnName, _newColumnDef) ? 1 : 0;
         }
@@ -274,10 +270,8 @@ public abstract class SchemaMigration extends Modifier
         Map<String, FieldMarshaller<?>> marshallers, String fieldName)
     {
         FieldMarshaller<?> marsh = marshallers.get(fieldName);
-        if (marsh == null) {
+        checkArgument(marsh != null,
-            throw new IllegalArgumentException(
+                      "'" + _tableName + "' does not contain field '" + fieldName + "'");
-                "'" + _tableName + "' does not contain field '" + fieldName + "'");
-        }
         return marsh;
     }
 

src/main/java/com/samskivert/depot/clause/SelectClause.java

@@ -32,6 +32,8 @@ import com.samskivert.depot.PersistentRecord;
 import com.samskivert.depot.expression.ColumnExp;
 import com.samskivert.depot.impl.FragmentVisitor;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 /**
  * Represents a complete select clause.
  */
@@ -64,17 +66,12 @@ public class SelectClause
                 continue;
             }
             if (clause instanceof WhereClause) {
-                if (_where != null) {
+                checkArgument(_where == null, "Query can't contain multiple Where clauses.");
-                    throw new IllegalArgumentException(
-                        "Query can't contain multiple Where clauses.");
-                }
                 _where = (WhereClause) clause;
 
             } else if (clause instanceof FromOverride) {
-                if (_fromOverride != null) {
+                checkArgument(_fromOverride == null,
-                    throw new IllegalArgumentException(
+                              "Query can't contain multiple FromOverride clauses.");
-                        "Query can't contain multiple FromOverride clauses.");
-                }
                 _fromOverride = (FromOverride) clause;
 
             } else if (clause instanceof Join) {
@@ -84,31 +81,20 @@ public class SelectClause
                 _disMap.put(((FieldDefinition) clause).getField(), ((FieldDefinition) clause));
 
             } else if (clause instanceof OrderBy) {
-                if (_orderBy != null) {
+                checkArgument(_orderBy == null, "Query can't contain multiple OrderBy clauses.");
-                    throw new IllegalArgumentException(
-                        "Query can't contain multiple OrderBy clauses.");
-                }
                 _orderBy = (OrderBy) clause;
 
             } else if (clause instanceof GroupBy) {
-                if (_groupBy != null) {
+                checkArgument(_groupBy == null, "Query can't contain multiple GroupBy clauses.");
-                    throw new IllegalArgumentException(
-                        "Query can't contain multiple GroupBy clauses.");
-                }
                 _groupBy = (GroupBy) clause;
 
             } else if (clause instanceof Limit) {
-                if (_limit != null) {
+                checkArgument(_limit == null, "Query can't contain multiple Limit clauses.");
-                    throw new IllegalArgumentException(
-                        "Query can't contain multiple Limit clauses.");
-                }
                 _limit = (Limit) clause;
 
             } else if (clause instanceof ForUpdate) {
-                if (_forUpdate != null) {
+                checkArgument(_forUpdate == null,
-                    throw new IllegalArgumentException(
+                              "Query can't contain multiple For Update clauses.");
-                        "Query can't contain multiple For Update clauses.");
-                }
                 _forUpdate = (ForUpdate) clause;
 
             } else {

src/main/java/com/samskivert/depot/clause/WhereClause.java

@@ -22,6 +22,8 @@ package com.samskivert.depot.clause;
 
 import com.samskivert.depot.expression.SQLExpression;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 /**
  * Currently only exists as a type without any functionality of its own.
  */
@@ -50,10 +52,8 @@ public abstract class WhereClause implements QueryClause
      */
     protected void validateTypesMatch (Class<?> qClass, Class<?> kClass)
     {
-        if (!qClass.equals(kClass)) {
+        checkArgument(qClass.equals(kClass),
-            throw new IllegalArgumentException(
+                      "Class mismatch between persistent record and key in query " +
-                "Class mismatch between persistent record and key in query " +
+                      "[qtype=%s, ktype=%s].", qClass.getSimpleName(), kClass.getSimpleName());
-                "[qtype=" + qClass.getSimpleName() + ", ktype=" + kClass.getSimpleName() + "].");
-        }
     }
 }