Mapper接口增加selectOne方法。

abel533 · abel533 · commit de9eaa7409fb · 2015-04-05T10:54:35.000+08:00
diff --git a/src/main/java/com/github/abel533/mapper/Mapper.java b/src/main/java/com/github/abel533/mapper/Mapper.java
@@ -40,6 +40,9 @@
  */
 public interface Mapper<T> {
 
+    @SelectProvider(type = MapperProvider.class, method = "dynamicSQL")
+    T selectOne(T record);
+
     @SelectProvider(type = MapperProvider.class, method = "dynamicSQL")
     List<T> select(T record);
 
diff --git a/src/main/java/com/github/abel533/mapper/MapperProvider.java b/src/main/java/com/github/abel533/mapper/MapperProvider.java
@@ -48,6 +48,27 @@ public MapperProvider(Class<?> mapperClass, MapperHelper mapperHelper) {
         super(mapperClass, mapperHelper);
     }
 
+    /**
+     * 查询
+     *
+     * @param ms
+     * @return
+     */
+    public SqlNode selectOne(MappedStatement ms) {
+        Class<?> entityClass = getSelectReturnType(ms);
+        //修改返回值类型为实体类型
+        setResultType(ms, entityClass);
+        List<SqlNode> sqlNodes = new ArrayList<SqlNode>();
+        //静态的sql部分:select column ... from table
+        sqlNodes.add(new StaticTextSqlNode("SELECT "
+                + EntityHelper.getSelectColumns(entityClass)
+                + " FROM "
+                + tableName(entityClass)));
+        //将if添加到<where>
+        sqlNodes.add(new WhereSqlNode(ms.getConfiguration(), getAllIfColumnNode(entityClass)));
+        return new MixedSqlNode(sqlNodes);
+    }
+
     /**
      * 查询
      *
@@ -66,15 +87,9 @@ public SqlNode select(MappedStatement ms) {
                 + tableName(entityClass)));
         //将if添加到<where>
         sqlNodes.add(new WhereSqlNode(ms.getConfiguration(), getAllIfColumnNode(entityClass)));
-        StringBuilder orderBy = new StringBuilder();
-        for (EntityHelper.EntityColumn column : EntityHelper.getColumns(entityClass)) {
-            if (column.getOrderBy() != null) {
-                orderBy.append(column.getColumn()).append(" ").append(column.getOrderBy()).append(",");
-            }
-        }
-        if (orderBy.length() > 0) {
-            orderBy.insert(0, "order by");
-            sqlNodes.add(new StaticTextSqlNode(orderBy.substring(0, orderBy.length() - 1)));
+        String orderByClause = EntityHelper.getOrderByClause(entityClass);
+        if (orderByClause.length() > 0) {
+            sqlNodes.add(new StaticTextSqlNode(orderByClause));
         }
         return new MixedSqlNode(sqlNodes);
     }
diff --git a/src/main/java/com/github/abel533/mapperhelper/EntityHelper.java b/src/main/java/com/github/abel533/mapperhelper/EntityHelper.java
@@ -242,6 +242,28 @@ public static EntityTable getEntityTable(Class<?> entityClass) {
         return entityTable;
     }
 
+    /**
+     * 获取默认的orderby语句
+     *
+     * @param entityClass
+     * @return
+     */
+    public static String getOrderByClause(Class<?> entityClass){
+        StringBuilder orderBy = new StringBuilder();
+        for (EntityHelper.EntityColumn column : getColumns(entityClass)) {
+            if (column.getOrderBy() != null) {
+                if(orderBy.length()!=0){
+                    orderBy.append(",");
+                }
+                orderBy.append(column.getColumn()).append(" ").append(column.getOrderBy());
+            }
+        }
+        if (orderBy.length() > 0) {
+            orderBy.insert(0, "ORDER BY ");
+        }
+        return orderBy.toString();
+    }
+
     /**
      * 获取全部列
      *
diff --git a/src/test/java/com/github/abel533/test/country/TestSelectOne.java b/src/test/java/com/github/abel533/test/country/TestSelectOne.java
@@ -0,0 +1,84 @@
+package com.github.abel533.test.country;
+
+import com.github.abel533.mapper.CountryMapper;
+import com.github.abel533.mapper.MybatisHelper;
+import com.github.abel533.model.Country;
+import org.apache.ibatis.exceptions.TooManyResultsException;
+import org.apache.ibatis.session.SqlSession;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * 通过实体类属性进行查询
+ *
+ * @author liuzh
+ */
+public class TestSelectOne {
+
+    /**
+     * 查询全部
+     */
+    @Test(expected = TooManyResultsException.class)
+    public void testDynamicSelectAll() {
+        SqlSession sqlSession = MybatisHelper.getSqlSession();
+        try {
+            CountryMapper mapper = sqlSession.getMapper(CountryMapper.class);
+            Country country = mapper.selectOne(new Country());
+        } finally {
+            sqlSession.close();
+        }
+    }
+
+    /**
+     * 入参为null时查询全部
+     */
+    @Test(expected = TooManyResultsException.class)
+    public void testDynamicSelectAllByNull() {
+        SqlSession sqlSession = MybatisHelper.getSqlSession();
+        try {
+            CountryMapper mapper = sqlSession.getMapper(CountryMapper.class);
+            mapper.selectOne(null);
+        } finally {
+            sqlSession.close();
+        }
+    }
+
+    /**
+     * 根据查询条件进行查询
+     */
+    @Test
+    public void testDynamicSelect() {
+        SqlSession sqlSession = MybatisHelper.getSqlSession();
+        try {
+            CountryMapper mapper = sqlSession.getMapper(CountryMapper.class);
+            Country country = new Country();
+            country.setCountrycode("CN");
+            Country result = mapper.selectOne(country);
+
+            Assert.assertEquals(true, result.getId() == 35);
+            Assert.assertEquals("China", result.getCountryname());
+        } finally {
+            sqlSession.close();
+        }
+    }
+
+    /**
+     * 查询不存在的结果
+     */
+    @Test
+    public void testDynamicSelectZero() {
+        SqlSession sqlSession = MybatisHelper.getSqlSession();
+        try {
+            CountryMapper mapper = sqlSession.getMapper(CountryMapper.class);
+            Country country = new Country();
+            country.setCountrycode("CN");
+            country.setCountryname("天朝");//实际上是 China
+            Country result = mapper.selectOne(country);
+
+            Assert.assertNull(result);
+        } finally {
+            sqlSession.close();
+        }
+    }
+
+}
