解决DataBase只有一个Read节点时，而且没有写weight属性，导致权重选择出异常的问题，同时在build xmlConfig时，强制验证Read节点是否写了Weight属性，当Read节点大于2时，其中一个read节点没有写weight属性，直接抛异常

src/SmartSql.Test.Unit/ConfigBuilder/XmlConfigLoaderTest.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Text;
 using SmartSql.ConfigBuilder;
+using SmartSql.Exceptions;
 using Xunit;
 
 namespace SmartSql.Test.Unit.ConfigBuilder
@@ -14,5 +15,18 @@ public void Load()
             var configLoader = new XmlConfigBuilder(ResourceType.File, "SmartSqlMapConfig.xml");
             var config = configLoader.Build();
         }
+        [Fact]
+        public void LoadFailTest()
+        {
+            try
+            {
+                var configLoader = new XmlConfigBuilder(ResourceType.File, "SmartSqlMapConfig2.xml");
+                var config = configLoader.Build();
+            }
+            catch (SmartSqlException ex)
+            {                  
+                Assert.StartsWith( "Read Nodes must have Weight attribute",ex.Message);
+            }
+        }
     }
 }

src/SmartSql.Test.Unit/SmartSql.Test.Unit.csproj

@@ -131,6 +131,9 @@
     <None Update="Maps\T_Entity.xml">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
+    <None Update="SmartSqlMapConfig2.xml">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
     <None Update="SmartSqlMapConfig.json">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>

src/SmartSql.Test.Unit/SmartSqlMapConfig.xml

@@ -53,7 +53,7 @@
         <DbProvider Name="${DbProvider}"/>
         <Write Name="WriteDB" ConnectionString="${ConnectionString}"/>
         <Read Name="ReadDb-1" ConnectionString="${ConnectionString}" Weight="100"/>
-        <Read Name="ReadDb-2" ConnectionString="${ConnectionString}" Weight="100"/>
+        <Read Name="ReadDb-2" ConnectionString="${ConnectionString}"  Weight="100"  />
     </Database>
     <TypeHandlers>
         <TypeHandler PropertyType="SmartSql.Test.Entities.UserInfo,SmartSql.Test" Type="${JsonTypeHandler`}">

src/SmartSql.Test.Unit/SmartSqlMapConfig2.xml

@@ -0,0 +1,99 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<SmartSqlMapConfig xmlns="http://SmartSql.net/schemas/SmartSqlMapConfig.xsd">
+    <Settings IgnoreParameterCase="false" ParameterPrefix="$" IsCacheEnabled="true" EnablePropertyChangedTrack="true"
+              IgnoreDbNull="true"/>
+    <Properties>
+        <!--    <Property Name="Redis" Value="localhost"/>-->
+        <Property Name="DbProvider" Value="MsSqlServer"/>
+        <Property Name="ConnectionString"
+                  Value="Data Source=.;Initial Catalog=SmartSqlTestDB;Integrated Security=True"/>
+        <Property Name="JsonTypeHandler`" Value="SmartSql.TypeHandler.JsonTypeHandler`1,SmartSql.TypeHandler"/>
+        <Property Name="JsonTypeHandler" Value="SmartSql.TypeHandler.JsonTypeHandler,SmartSql.TypeHandler"/>
+        <Property Name="ScriptBuilder" Value="SmartSql.ScriptTag.ScriptBuilder,SmartSql.ScriptTag"/>
+        <Property Name="RedisCacheProvider" Value="SmartSql.Cache.Redis.RedisCacheProvider,SmartSql.Cache.Redis"/>
+    </Properties>
+    <AutoConverters>
+        <AutoConverter Name="NoneConverter">
+            <Tokenizer Name="None"/>
+            <Converter Name="None"/>
+        </AutoConverter>
+        <AutoConverter Name="Default" Default="true">
+            <Tokenizer Name="Default"/>
+            <Converter Name="Pascal"/>
+        </AutoConverter>
+        <AutoConverter Name="PascalConverter">
+            <Tokenizer Name="Default">
+                <Properties>
+                    <Property Name="IgnorePrefix" Value=""/>
+                    <Property Name="Delimiter" Value="_"/>
+                    <Property Name="UppercaseSplit" Value="false"/>
+                </Properties>
+            </Tokenizer>
+            <Converter Name="Pascal"/>
+        </AutoConverter>
+        <AutoConverter Name="DelimiterConverter">
+            <Tokenizer Name="Default">
+                <Properties>
+                    <Property Name="IgnorePrefix" Value="col_"/>
+                    <Property Name="Delimiter" Value="_"/>
+                    <Property Name="UppercaseSplit" Value="true"/>
+                </Properties>
+            </Tokenizer>
+            <Converter Name="Delimiter">
+                <Properties>
+                    <Property Name="Prefix" Value="Col_"/>
+                    <Property Name="Delimiter" Value="_"/>
+                    <Property Name="Mode" Value="FirstUpper"/>
+                </Properties>
+            </Converter>
+        </AutoConverter>
+    </AutoConverters>
+    <Database>
+        <!-- MsSqlServer: Microsoft.Data.SqlClient , SqlServer: System.Data.SqlClinet -->
+        <DbProvider Name="${DbProvider}"/>
+        <Write Name="WriteDB" ConnectionString="${ConnectionString}"/>
+        <Read Name="ReadDb-1" ConnectionString="${ConnectionString}" Weight="100"/>
+        <Read Name="ReadDb-2" ConnectionString="${ConnectionString}"  />
+    </Database>
+    <TypeHandlers>
+        <TypeHandler PropertyType="SmartSql.Test.Entities.UserInfo,SmartSql.Test" Type="${JsonTypeHandler`}">
+            <Properties>
+                <Property Name="DateFormat" Value="yyyy-MM-dd mm:ss"/>
+                <Property Name="NamingStrategy" Value="Camel"/>
+            </Properties>
+        </TypeHandler>
+        <TypeHandler Name="AnsiStringTypeHandler" Type="SmartSql.TypeHandlers.StringTypeHandler,SmartSql">
+            <Properties>
+                <Property Name="DbType" Value="AnsiString"/>
+            </Properties>
+        </TypeHandler>
+        <TypeHandler Name="AnsiStringFixedLengthTypeHandler" Type="SmartSql.TypeHandlers.StringTypeHandler,SmartSql">
+            <Properties>
+                <Property Name="DbType" Value="AnsiStringFixedLength"/>
+            </Properties>
+        </TypeHandler>
+        <TypeHandler Name="Json" Type="${JsonTypeHandler}"></TypeHandler>
+
+    </TypeHandlers>
+    <TagBuilders>
+        <TagBuilder Name="Script" Type="${ScriptBuilder}"/>
+    </TagBuilders>
+    <IdGenerators>
+        <IdGenerator Name="SnowflakeId" Type="SnowflakeId">
+            <Properties>
+                <Property Name="WorkerIdBits" Value="9"/>
+                <Property Name="WorkerId" Value="511"/>
+                <Property Name="Sequence" Value="14"/>
+            </Properties>
+        </IdGenerator>
+        <IdGenerator Name="DbSequence" Type="DbSequence">
+            <Properties>
+                <Property Name="Step" Value="10"/>
+                <Property Name="SequenceSql" Value="Select Next Value For IdSequence;"/>
+            </Properties>
+        </IdGenerator>
+    </IdGenerators>
+    <SmartSqlMaps>
+        <SmartSqlMap Path="Maps" Type="Directory"></SmartSqlMap>
+    </SmartSqlMaps>
+</SmartSqlMapConfig>

src/SmartSql/ConfigBuilder/XmlConfigBuilder.cs

@@ -28,7 +28,7 @@ public class XmlConfigBuilder : AbstractConfigBuilder
 
         private readonly IWordsConverterBuilder _wordsConverterBuilder = new WordsConverterBuilder();
         private readonly ITokenizerBuilder _tokenizerBuilder = new TokenizerBuilder();
-        
+
         public XmlConfigBuilder(ResourceType resourceType, string resourcePath, ILoggerFactory loggerFactory = null)
         {
             _resourceType = resourceType;
@@ -153,12 +153,8 @@ protected override void BuildDatabase()
             database.Write.DbProvider = database.DbProvider;
             var readDataSourceNodes = databaseNode.SelectNodes($"{CONFIG_PREFIX}:Read", XmlNsManager);
             if (readDataSourceNodes == null) return;
-            foreach (XmlNode readNode in readDataSourceNodes)
-            {
-                var readDb = ParseReadDataSource(readNode);
-                readDb.DbProvider = database.DbProvider;
-                database.Reads.Add(readDb.Name, readDb);
-            }
+            var readDataSources = this.ParseReadDataSource(readDataSourceNodes, database.DbProvider);
+            database.Reads.AddRange(readDataSources);
         }
 
         private DbProvider ParseDbProvider(XmlNode dbProviderNode)
@@ -226,34 +222,46 @@ private WriteDataSource ParseWriteDataSource(XmlNode writeDataSourceNode)
             {
                 writeDataSource.ConnectionString = connectionString;
             }
-
+          
             return writeDataSource;
         }
-        private ReadDataSource ParseReadDataSource(XmlNode readDataSourceNode)
+        private IDictionary<string, ReadDataSource> ParseReadDataSource(XmlNodeList readDataSourceNodes, DbProvider dbProvider)
         {
-            if (readDataSourceNode == null)
-            {
-                throw new SmartSqlException("ReadDataSource can not be null.");
-            }
-            var readDataSource = new ReadDataSource();
-            if (readDataSourceNode.Attributes.TryGetValueAsString(nameof(ReadDataSource.Name), out string name, SmartSqlConfig.Properties)
-            )
-            {
-                readDataSource.Name = name;
-            }
-            if (readDataSourceNode.Attributes.TryGetValueAsString(nameof(ReadDataSource.ConnectionString), out string connectionString, SmartSqlConfig.Properties)
-            )
-            {
-                readDataSource.ConnectionString = connectionString;
-            }
-            if (readDataSourceNode.Attributes.TryGetValueAsInt32(nameof(ReadDataSource.Weight), out int weight, SmartSqlConfig.Properties)
-            )
-            {
-                readDataSource.Weight = weight;
+            var readDataSources = new Dictionary<string, ReadDataSource>();
+            var s = new List<string>();           
+            foreach (XmlNode readDataSourceNode in readDataSourceNodes)
+            {  
+
+                var readDataSource = new ReadDataSource();
+                if (readDataSourceNode.Attributes.TryGetValueAsString(nameof(ReadDataSource.Name), out string name, SmartSqlConfig.Properties)                )
+                {
+                    readDataSource.Name = name;
+                }
+                else
+                {
+                      throw new SmartSqlException($"Read Nodes must have Name attribute");
+                }
+                if (readDataSourceNode.Attributes.TryGetValueAsString(nameof(ReadDataSource.ConnectionString), out string connectionString, SmartSqlConfig.Properties)                )
+                {
+                    readDataSource.ConnectionString = connectionString;
+                }
+                if (readDataSourceNode.Attributes.TryGetValueAsInt32(nameof(ReadDataSource.Weight), out int weight, SmartSqlConfig.Properties)                )
+                {
+                    readDataSource.Weight = weight;
+                }
+                else
+                {
+                    if (readDataSourceNodes.Count > 1)
+                    {
+                         throw new SmartSqlException($"Read Nodes must have Weight attribute,Name is {readDataSource.Name}");
+                    }                  
+                }
+                readDataSource.DbProvider = dbProvider;
+                readDataSources.Add(readDataSource.Name, readDataSource);
             }
-
-            return readDataSource;
+            return readDataSources;
         }
+
         #endregion
         #region 3. TypeHandlers
         protected override void BuildTypeHandlers()
@@ -414,7 +422,7 @@ private void BuildAutoConverter(XmlNode autoConverterNode)
             var wordsConverter = BuildWordsConverter(wordsConverterNode);
 
             var autoConverter = new AutoConverter.AutoConverter(converterName, tokenizer, wordsConverter);
-                
+
             SmartSqlConfig.AutoConverters.Add(autoConverter.Name, autoConverter);
             if (isDefault)
             {
@@ -431,7 +439,7 @@ private ITokenizer BuildTokenizer(XmlNode tokenizerNode)
             var properties = ParseProperties(tokenizerNode);
             return _tokenizerBuilder.Build(tokenizerName, properties);
         }
-        
+
         private IWordsConverter BuildWordsConverter(XmlNode wordsConverterNode)
         {
             if (!wordsConverterNode.Attributes.TryGetValueAsString("Name", out String wordsConverterName, SmartSqlConfig.Properties))
@@ -441,10 +449,10 @@ private IWordsConverter BuildWordsConverter(XmlNode wordsConverterNode)
             var properties = ParseProperties(wordsConverterNode);
             return _wordsConverterBuilder.Build(wordsConverterName, properties);
         }
-        
+
         #endregion
-        
-        
+
+
         private IDictionary<String, object> ParseProperties(XmlNode parentNode)
         {
             var parametersNode = parentNode.SelectSingleNode($"{CONFIG_PREFIX}:Properties", XmlNsManager);

src/SmartSql/Utils/DictionaryExtensions.cs

@@ -39,6 +39,13 @@ public static void EnsureValue<TKey, TValue, TTypedValue>(this IDictionary<TKey,
                 throw new SmartSqlException($"Can not find Parameter:{key}!");
             }
         }
+        public static void AddRange<TKey, TValue>(this IDictionary<TKey,TValue> dic, IDictionary<TKey,TValue> collection)
+        {
+            foreach(var  item in collection)
+            {
+                dic.Add(item);
+            }
+        }
 
     }
 }

src/SmartSql/Utils/WeightFilter.cs

@@ -11,6 +11,7 @@ namespace SmartSql.Utils
     /// </summary>
     public class WeightFilter<T>
     {
+
         /// <summary>
         /// 选举权重源
         /// </summary>
@@ -20,7 +21,16 @@ public WeightSource Elect(IEnumerable<WeightSource> inWeightSources)
         {
             var random = new Random((int)Stopwatch.GetTimestamp());
             var weightSources = inWeightSources.ToList();
-            int totalWeight = weightSources.Sum(source => source.Weight);
+            int totalWeight = 0;
+            if (weightSources.Count ==1)
+            {
+                return weightSources[0];
+            }
+            else
+            {
+              totalWeight=weightSources.Sum(source => source.Weight);
+            }
+
             int position = random.Next(1, totalWeight);
             return FindByPosition(weightSources, position);
         }