1. Function接口，提供两个方法：
apply方法：
可以自定义自己想实现的功能
1 @Nullable T apply(@Nullable F input);
１. 实例：
代码语言：javascript复制 1 import com.google.common.base.Function;
2 import com.google.common.base.Joiner;
3 import org.junit.Test;
4 import org.slf4j.Logger;
5 import org.slf4j.LoggerFactory;
6
7 /**
8 * author: 龚细军
9 * class-aim:
10 */
11 public class Demo<F, T> {
12
13 private Logger logger = LoggerFactory.getLogger(Demo.class);
14
15 public void demoFunction(F input, Function<F, T> function) throws Exception {
16
17 logger.info(String.valueOf(function.apply(input)));
18 }
19
20 @Test
21 public void show() {
22
23 Function<F, T> functionTest = new Function<F, T>() {
24 @Override
25 public T apply(F input) {
26 return (T) Integer.valueOf(String.valueOf(input));
27 }
28 };
29
30 try {
31 demoFunction((F) "123", functionTest);
32 } catch (Exception e) {
33 logger.error(Joiner.on("").join("{}show发生异常", e));
34 }
35 }
36 }一般而言，使用这种方法，可以让我们避免做重复的事情，比如，我们在使用jdbc时，会出现大量重复的代码，我们可以采用Function<F,T>来进行函数编程，简化代码：
代码语言：javascript复制 2
3
4 import com.google.common.base.Function;
5 import com.google.common.collect.Lists;
6 import com.qunar.fresh.bean.PageVistor;
7 import com.qunar.fresh.bean.dbBean;
8 import org.slf4j.Logger;
9 import org.slf4j.LoggerFactory;
10 import org.springframework.beans.factory.BeanFactory;
11 import org.springframework.context.support.FileSystemXmlApplicationContext;
12
13 import java.sql.*;
14 import java.util.List;
15
16
17 /**
18 * author: 龚细军
19 * class-aim: dao-dbDemo
20 */
21 public class DbUtil<F, T> {
22
23 private static final String CONFIG_PROPERTIES = "classpath:Beans.xml";
24
25
26 static Logger logger = LoggerFactory.getLogger(DbUtil.class);
27
28 private Connection connection = null;
29 private static dbBean dataBean;
30 private PreparedStatement preparedStatement = null;
31 private ResultSet resultSet = null;
32 private List<PageVistor> PageVisitors;
33
34 static {
35 try {
36 BeanFactory beanFactory = new FileSystemXmlApplicationContext(CONFIG_PROPERTIES);
37
38 dataBean = (dbBean) beanFactory.getBean("dbBean");
39 Class.forName(dataBean.getDriver());
40 } catch (ClassNotFoundException e) {
41 logger.info(String.format("sql exception0 : %s", e));
42 }
43 }
44
45
46 private T execute(Function<F, T> function, String sql) {
47
48 T execResult = null;
49
50 try {
51 connection = DriverManager.getConnection(dataBean.getUrl(),
52 dataBean.getUsername(), dataBean.getPassword());
53 preparedStatement = connection.prepareStatement(sql);
54 execResult = function.apply(null);
55 } catch (SQLException e) {
56 logger.info(String.format("sql exception１ : %s", e));
57 } finally {
58 try {
59 if (!preparedStatement.isClosed())
60 preparedStatement.close();
61 if (!connection.isClosed())
62 connection.close();
63 } catch (SQLException e) {
64 logger.info(String.format("sql exception２ : %s", e));
65 }
66 }
67
68 return execResult;
69 }
70
71
72 public List<PageVistor> Query(String sql) {
73
74
75 PageVisitors = Lists.newArrayList();
76
77 Function<F, T> function = new Function<F, T>() {
78
79 @Override
80 public T apply(F input) {
81
82
83 try {
84 resultSet = preparedStatement.executeQuery();
85
86 while (resultSet.next()) {
87 PageVisitors.add(new PageVistor(0, "", resultSet.getString(1)
88 , resultSet.getInt(2)));
89 }
90 } catch (SQLException e) {
91 logger.info(String.format("sql exception3 : %s", e));
92 } finally {
93 try {
94
95 if (resultSet != null) resultSet.close();
96
97 } catch (SQLException e) {
98 logger.info(String.format("sql exception４ : %s", e));
99 }
100 }
101
102 return null;
103 }
104 };
105 this.execute(function, sql);
106
107 return PageVisitors;
108 }
109
110
111 public void Update(String sql) {
112
113 Function<F, T> function = new Function<F, T>() {
114
115 @Override
116 public T apply(F input) {
117
118 try {
119 int var = preparedStatement.executeUpdate();
120 if (var == 0)
121 logger.error("{} 更新数据失败");
122 } catch (SQLException e) {
123 logger.info(String.format("sql exception3 : %s", e));
124 }
125 return null;
126 }
127 };
128
129 this.execute(function, sql);
130 }
131 }
